Un dispositivo semiconductor de nitruro de láser que comprende: un sustrato de semiconductor de nitruro, una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo, una capa activa y un P-capa de semiconductor de tipo laminado en o sobre el sustrato de semiconductor de nitruro, y tiene una franja en forma de región de la guía de onda de la luz láser, y una emisión final del film lado de la superficie de protección y una superficie del extremo trasero lado opusieron a la misma película protectora sobre las superficies extremas de la resonancia, encerrando la región de guía de ondas, en el cual el sustrato de semiconductor de nitruro tiene una región de radiación luminosa que absorbe la luz emitida por la capa activa y emite radiación luminosa con una longitud de onda más larga que la longitud de onda de la luz emitida, y la parte trasera de cine lado de la superficie de protección incluye una superficie final primera película de protección con una mayor reflectividad para la longitud de onda de la radiación luminosa, y una película superficial segundo extremo de protección con una mayor reflectividad para la longitud de onda de la luz emitida desde la capa activa, la emisión final del film lado de la superficie de protección incluye una superficie final tercera película de protección con una mayor reflectividad para la longitud de onda de la radiación luminosa y con una menor reflectividad de la longitud de onda de la luz emitida desde la capa activa, la emisión final del film lado de la superficie de protección cubre la banda región de guía de ondas en forma de una emisión o del lado de la superficie final de la resonancia, la superficie del extremo películas protectoras más cobertura ambos extremos de la superficie del sustrato semiconductor de nitruro, y en donde la superficie final segunda película de protección es insertado por la capa de semiconductor de nitruro y la superficie final primera película de protección.
2. Un dispositivo semiconductor de nitruro de láser que comprende: un sustrato de semiconductor de nitruro, una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo, una capa activa y un P-capa de semiconductor de tipo laminado en o sobre el sustrato de semiconductor de nitruro, y tiene una franja en forma de región de la guía de onda de la luz láser, y una emisión final del film lado de la superficie de protección y una superficie del extremo trasero lado opusieron a la misma película protectora sobre las superficies extremas de la resonancia, encerrando la región de guía de ondas, en el cual el sustrato de semiconductor de nitruro tiene una región de radiación luminosa que absorbe la luz emitida por la capa activa y emite radiación luminosa con una longitud de onda más larga que la longitud de onda de la luz emitida, la parte trasera de cine lado de la superficie de protección incluye una superficie final primera película de protección con una mayor reflectividad para la longitud de onda de la radiación luminosa, y un segunda superficie de película de protección final con una mayor reflectividad para la longitud de onda de la luz emitida desde la capa activa, la emisión final del film lado de la superficie de protección incluye una superficie final tercera película de protección con una mayor reflectividad para la longitud de onda de la radiación luminosa, la primera película de la superficie final de protección y / o la superficie final tercera película de protección tiene una baja reflectividad de la longitud de onda de la luz emitida desde la capa activa, la emisión final del film lado de la superficie de protección cubre la banda región de guía de ondas en forma de una emisión o del lado final superficie de la resonancia de la superficie final películas protectoras más cubrir tanto las superficies finales del sustrato de semiconductor de nitruro, y en donde la superficie final segunda película protectora es insertado por la capa de semiconductor de nitruro y la superficie final primera película protectora.
3. El dispositivo semiconductor de nitruro de láser, según la reivindicación 1, donde la emisión final del film lado de la superficie de protección incluye una superficie final cuarta película de protección con una mayor reflectividad para la longitud de onda de la luz emitida desde la capa activa (104).
4. El dispositivo semiconductor de nitruro de láser según la reivindicación 3, caracterizado porque cada una de las primera, segunda, tercera y cuarta de superficie final películas de protección tiene una sola capa o estructura de múltiples capas.
5. Un dispositivo semiconductor de nitruro de láser que comprende: un sustrato de semiconductor de nitruro, una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo, una capa activa y un P-capa de semiconductor de tipo laminado en o sobre el sustrato de semiconductor de nitruro, y tiene una franja en forma de región de la guía de onda de la luz láser, y una emisión final del film lado de la superficie de protección y una superficie del extremo trasero lado opusieron a la misma película protectora sobre las superficies extremas de la resonancia, encerrando la región de guía de ondas, en el cual el sustrato de semiconductor de nitruro tiene una región de radiación luminosa que absorbe la luz emitida por la capa activa y emite radiación luminosa con una longitud de onda más larga que la longitud de onda de la luz emitida, la parte trasera de cine lado de la superficie de protección incluye una superficie final primera película de protección con una mayor reflectividad para la longitud de onda de la radiación luminosa, y un segunda superficie de película de protección final con una mayor reflectividad para la longitud de onda de la luz emitida desde la capa activa, la emisión final del film lado de la superficie de protección incluye una superficie final tercera película de protección con una mayor reflectividad para la longitud de onda de la radiación luminosa, la primera y la superficie del segundo extremo películas protectoras son laminados a fin de, al menos parcialmente se superponen unos a otros, la emisión final del film lado de la superficie de protección cubre la banda región de guía de ondas en forma de una emisión o de superficie final lado de la resonancia, la superficie del extremo películas protectoras más cobertura ambos extremos de la superficie del sustrato semiconductor de nitruro, y en donde la superficie final segunda película de protección es insertado por la capa de semiconductor de nitruro y la superficie final primera película de protección.
6. El dispositivo semiconductor de nitruro de láser, según la reivindicación 4, en donde las películas de tercera y cuarta final superficie de protección son laminados a fin de, al menos parcialmente se superponen unos a otros.
7. El dispositivo semiconductor de nitruro de láser, según la reivindicación 1, donde la superficie final segunda película protectora se forma en contacto con la capa de semiconductor de nitruro.
8. El dispositivo semiconductor de nitruro de láser según la reivindicación 3, caracterizado porque la superficie final cuarta película protectora se forma en contacto con la capa de semiconductor de nitruro.
9. El dispositivo semiconductor de nitruro de láser que comprende: un sustrato de semiconductor de nitruro, una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo, una capa activa y un P-capa de semiconductor de tipo laminado en o sobre el sustrato de semiconductor de nitruro, y tiene una franja en forma de región de la guía de onda de la luz láser, y la superficie final películas protectoras en ambos extremos superpuestos a la superficie de la resonancia de la región de guía de ondas, en el cual el sustrato de semiconductor de nitruro tiene una región de radiación luminosa que absorbe la luz emitida desde la capa activa y emite radiación luminosa con una longitud de onda más larga que la películas protectoras longitud de onda de la luz emitida, al menos uno de la superficie del extremo tiene una mayor reflectividad para la longitud de onda de la radiación luminosa de la región de la radiación luminosa, la región de la radiación luminosa tiene una densidad más baja de la luxación en comparación con la periferia del mismo, por lo menos uno de la superficie del extremo película de protección cubre la banda región de guía de ondas en forma de una emisión o de superficie final lado de la resonancia ~ la superficie del extremo más películas protectoras cubrir tanto las superficies finales del sustrato de semiconductor de nitruro, y en donde la superficie final segunda película de protección se intercala por el semiconductor de nitruro de cerveza y la superficie final primera película de protección.
10. Un dispositivo semiconductor de nitruro de láser que comprende: un sustrato de semiconductor de nitruro, una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo, una capa activa y un P-capa de semiconductor de tipo laminado en o sobre el sustrato de semiconductor de nitruro, y tiene una franja en forma de región de la guía de onda de la luz láser, y la superficie final películas protectoras en ambos extremos superpuestos a la superficie de la resonancia de la región de guía de ondas, en el cual el sustrato de semiconductor de nitruro tiene una región de radiación luminosa que absorbe la luz emitida desde la capa activa y emite radiación luminosa con una longitud de onda más larga que la películas protectoras longitud de onda de la luz emitida, al menos uno de la superficie del extremo tiene una mayor reflectividad para la longitud de onda de la radiación luminosa de la región de la radiación luminosa y la región de la radiación luminosa tiene una alta concentración de impurezas en comparación con la periferia del mismo, en menos uno de la superficie del extremo película de protección cubre la banda región de guía de ondas en forma de una emisión o de superficie final lado de la resonancia, la superficie del extremo más películas protectoras cubrir tanto las superficies finales del sustrato de semiconductor de nitruro, y en donde la superficie final segunda película de protección es insertado por el semiconductor de nitruro de algas y la superficie final primera película de protección.
11. El dispositivo semiconductor de nitruro de láser, según la reivindicación 10, en donde la impureza es al menos un elemento seleccionado del grupo formado por H, O, C y Si.
12. Un dispositivo semiconductor de nitruro de láser que comprende: un sustrato de semiconductor de nitruro, una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo, una capa activa y una capa de semiconductor de tipo laminado en o sobre el sustrato de semiconductor de nitruro, y tiene una franja región de guía de ondas en forma de de luz láser, y la superficie final películas protectoras en ambos extremos superpuestos a la superficie de la resonancia de la región de guía de ondas, en el cual el sustrato de semiconductor de nitruro tiene una región de radiación luminosa que absorbe la luz emitida desde la capa activa y emite radiación luminosa con una longitud de onda más larga que la longitud de onda de la luz emitida, al menos uno de la superficie del extremo películas protectoras tiene mayor reflectividad para la longitud de onda de la radiación luminosa de la región de la radiación luminosa, la capa activa tiene una emisión de luz de longitud de onda de 390 a 420 nm y las radiaciones luminosas tiene una longitud de onda de 550 a 600 nm, por lo menos un extremo de la superficie una película protectora cubre la banda región de guía de ondas en forma de una emisión o de superficie final lado de la resonancia: la superficie del extremo más películas protectoras cubrir tanto las superficies finales del sustrato de semiconductor de nitruro, y en donde la superficie final segunda película protectora es insertado por la capa de semiconductor de nitruro y la superficie final primera película de protección.
13. El dispositivo semiconductor de nitruro de láser, según la reivindicación 9, en donde la región de las radiaciones luminosas se forma en una forma de banda prácticamente paralelo a la región de guía de onda.
14. El dispositivo semiconductor de nitruro de láser, según la reivindicación 1, donde la región de guía de onda se forma por encima de la región de las radiaciones luminosas.
15. Un dispositivo semiconductor de nitruro de láser que comprende: un sustrato de semiconductor de nitruro), una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo, una capa activa y un P-capa de semiconductor de tipo laminado en o sobre el sustrato de semiconductor de nitruro, y tiene una raya - región en forma de guía de onda de la luz láser, y la superficie final películas protectoras en ambos extremos superpuestos a la superficie de la resonancia de la región de guía de ondas, en el cual el sustrato de semiconductor de nitruro tiene una región de radiación luminosa que absorbe la luz emitida desde la capa activa y emite radiación luminosa con una longitud de onda más larga que la longitud de onda de la luz emitida, por lo menos una de las películas de protección de superficie final tiene una mayor reflectividad para la longitud de onda de la radiación luminosa de la región de la radiación luminosa y la región de guía de onda se formó en una región que es espacio lejos de la radiación luminosa región, al menos uno de la superficie del extremo película de protección cubre la banda región de guía de ondas en forma de una emisión o de superficie final lado de la resonancia, la superficie del extremo más películas protectoras cubrir tanto las superficies finales del sustrato de semiconductor de nitruro, y en donde el segundo extremo de superficie la película protectora es insertado por la capa de semiconductor de nitruro y la superficie final primera película de protección.
16. Un aparato de láser que incluye el dispositivo semiconductor de nitruro de láser, según la reivindicación 9, y un detector que detecta la emisión de luz del láser semiconductor de nitruro de dispositivo, en el que el detector tiene una sensibilidad espectral en una longitud de onda) ~ ex de la radiación luminosa superior a una longitud de onda ) ? LD de la luz emitida de nitruro de dispositivo láser de semiconductor.
17. Un aparato de láser que incluye el dispositivo semiconductor de nitruro de láser, según la reivindicación 1, y un detector que detecta la emisión de luz del láser semiconductor de nitruro de dispositivo, en el que el detector tiene una sensibilidad espectral en una longitud de onda ? ex de la radiación luminosa superior a una longitud de onda ? LD de la luz emitida del nitruro de dispositivo láser de semiconductor.
Descripción:
ANTECEDENTES DE LA INVENCIÓN
1. Técnico de Campo
La presente invención se relaciona con un dispositivo láser de semiconductor con una película de protección dieléctrica forma en la superficie una capa final de semiconductores utilizando un semiconductor de nitruro, y más concretamente a un máximo de dispositivos semiconductores utilizando un láser de semiconductor de nitruro de sustrato. Un grupo III-V semiconductor de nitruro incluyendo GaN, AlN y posada, y un cristal mezcla de ellos como Algan grupo, grupo y grupo de InGaN AlInGaN puede darse como la composición específica de los dispositivos semiconductores.
2. Descripción de las Obras Relacionadas
Elementos semiconductores de nitruro de que la emisión de luz de la gama ultravioleta de la relativamente corta longitud de onda de la gama de luz visible, que incluye rojos, y son ampliamente utilizados como materias que componen un diodo láser de semiconductor (LD), un diodo emisor de luz (LED), y así sucesivamente. En estos años, se están haciendo para mejorar la miniaturización, la vida, la fiabilidad y potencia de salida, y se utilizan principalmente para las fuentes de luz en los dispositivos electrónicos, como computadoras personales y dispositivos de DVD para la electrónica, dispositivos médicos, dispositivos de mecanizado, las comunicaciones de fibra óptica , y así sucesivamente.
Este tipo de elementos semiconductores de nitruro de tener una estructura laminada sobre todo con una capa de amortiguación, una n-capa de contacto de tipo, una capa de prevención de crack, una n-capa de revestimiento tipo, una n-luz capa de tipo guía, una capa activa, un p - la capa de tipo de confinamiento de electrones, un P-luz de la capa de tipo guía, un P-capa de revestimiento tipo y un P-capa de contacto de tipo que son sucesivamente laminada sobre un substrato de zafiro. Además, una cresta en forma de banda está formada por el grabado, o un estrechamiento de la capa actual es creado para brindar una franja región en forma de guía de ondas. El tipo n y p-capas de contacto de tipo se proporcionan con la N-lado y lado de los electrodos p, respectivamente. Se aplica corriente a través de los electrodos, por lo tanto, la capa activa, emite luz. Resonancia superficies se forman en una longitud de resonancia prescrito en el extremo las dos superficies de la región de guía de onda. La luz del láser es emitida desde la superficie de la resonancia.
Películas de protección aislante, o similares, se forman en la superficie de resonancia para proteger a las capas de semiconductores, de aire y para proporcionar la diferencia entre el lado de la reflectividad de las emisiones y la parte trasera. La película protectora en la parte trasera tiene una alta reflectividad en comparación con la película protectora en la parte de las emisiones. Esto puede mejorar la potencia de salida.
En el dispositivo semiconductor de láser de películas protectoras con una diferencia grande entre la reflectividad en la parte trasera y la parte de emisión, la luz que se filtra de la región de guía de onda (luz difusa) no es propenso a los egresos de la parte trasera, por lo que se emite desde la superficie del extremo de el lado de las emisiones. En consecuencia, la luz difusa puede causar el ruido en el patrón de medida de campo (FFP), y, en consecuencia, la no distribución de Gauss. A fin de evitar las emisiones hacia el exterior de la luz parásita, una película no-transparentes, como la película de metal, se pueden formar de manera que cubra la superficie final del sustrato. (Véase en materia de Patentes Documento 1: Japonesa de Patentes Laid-Open Publication TOKUKAI N º 2002-280663)
Sin embargo, en el caso de que una película no es transparente parcialmente formado en la superficie de la resonancia en el lado de la emisión de luz, un proceso adicional, como la máscara de proceso de formación, es obligatorio. En particular, en el caso de que, después de una oblea se divide en la barra de elementos en forma de láser, una superficie final se forma una película protectora sobre la superficie del extremo de la barra de elemento en forma de láser, es difícil incluso para formar una máscara en la alineación exacta. Por esta razón, es más difícil controlar la región en la que la superficie del extremo película de protección debe ser formado. En particular, en el caso de que un material metálico que se utiliza como una película no transparente, si el control de alineación es pobre, hay un problema que un cortocircuito puede ocurrir. Además, en el caso de que una película no-transparente se forma en una gran región, las características de unión entre la película no-transparentes y la capa de semiconductor o de una película protectora disminuye debido a la diferencia del coeficiente de expansión térmica entre el material metálico y la capa de semiconductores en el caso de algunos materiales. En este caso, un problema que la película no transparente es propenso a pelar surge.
RESUMEN DE LA INVENCIÓN
Por lo tanto, la presente invención tiene por objeto proporcionar un dispositivo semiconductor de nitruro de láser que elimina el deterioro de FFP por perdida la luz emitida por una superficie final en el lado de emisión para proporcionar características excelente de la viga, y no mal funcionamiento y, además, tienen características de vida excelente .
El inventor de la presente invención se ha estudiado con diligencia para resolver el problema anterior, y, como resultado, desarrolló la presente invención. El desarrollo de la presente invención se basa en conclusiones que una película de la superficie final de un dispositivo láser de control de luces láser y la luz parásita que distinguen a ser controlado por la película superficial final en el control de alto nivel, en otras palabras, puede proporcionar un dispositivo láser que tiene tanto dos funciones de salida eficiente de la luz LD del dispositivo de láser y el confinamiento eficaz para la prevención de la luz parásita de salida. Un dispositivo láser semiconductor de nitruro de acuerdo con la presente invención comprende un sustrato de semiconductor de nitruro de 101 y una capa de semiconductor de nitruro de que tiene un n-capas de semiconductores tipo 102, una capa activa 104 y un P-103 capa de semiconductor de tipo laminado o por encima del semiconductor de nitruro sustrato de 101, y tiene una franja región en forma de guía de onda de la luz láser, y la superficie final de 110 películas protectoras final los dos superficies sensiblemente perpendicular a la región de guía de onda. El sustrato de semiconductor de nitruro de 101 tiene una región de las radiaciones luminosas 112 que absorbe la luz emitida desde la capa activa 104 y emite radiación luminosa con una longitud de onda más larga que la longitud de onda de la luz emitida. La superficie final películas protectoras 110 tienen un alto grado de reflexión para la longitud de onda de la radiación luminosa de la región de las radiaciones luminosas 112. En concreto, la superficie del extremo películas de protección tienen una reflectividad para ? ex superior ? LD, LD, donde ? es la longitud de onda de la luz emitida del nitruro de dispositivo láser de semiconductor, y es un ex ? longitud de onda de la radiación luminosa. En otras palabras, una superficie de película de protección final con una reflectividad de la luz láser de longitud de onda ? LD superior a la radiación luminosa de longitud de onda ? ex del sustrato utilizado. En consecuencia, la superficie de película de protección final sirve como una superficie reflectante de gama alta película protectora de la radiación luminosa que tiene una reflectividad superior de la radiación luminosa de longitud de onda ? ex. Dado que la superficie final tiene una película protectora de transmisión de la radiación luminosa de longitud de onda ? ex mayor que la luz láser de longitud de onda ? LD, es posible ofrecer ambos efectos preferible eficiente de salida de la luz láser y corte eficiente-off de la radiación luminosa.
Light emitted from the active layer is confined in a region sandwiched by cladding layers with a refractive index lower than the active layer in the vertical direction (the direction substantially perpendicular to the lamination plane), and, additionally, is confined in a stripe shape corresponding to a current injection region in the transverse direction (the horizontal direction relative to the lamination surface). Resonance surfaces are formed in the region where the light from the active layer is confined, thus, a stripe-shaped waveguide is formed. However, light leaks from the waveguide region to other regions. According to the present invention, a non-transparent film that does not allow the light from the waveguide region (stray light) to pass is not provided, but the end surface protective film having a high reflectivity for a wavelength that is converted and different from the stray light. Therefore, mixture of noise in laser light is suppressed. In the present invention, specifically, a high reflectivity can be approximately 50% to 100%, and preferably 70 to 100%. A low reflectivity can be the range of approximately 18% or less of the end surface of gallium nitride group compound semiconductor without protective film.
In a nitride semiconductor laser device according to a second aspect of the present invention, the end surface protective films 110 are located on the end surfaces both on the emission side and the rear side.
In this construction, it is possible to efficiently suppress outward emission of stray light. Specifically, light from the laser device is incident on PD as a detector (photo detector) that is located on a part of a light path of emitted light or reflected light opposed thereto (light from the rear-side end surface) in the resonance direction. The detector detects each light power, and the driving of the laser device is controlled based on the information. For this reason, elimination of the luminescent radiation component that is a noise component for PD improves the control. Accordingly, it is preferable that the aforementioned protective films are formed at least on the both end surfaces of the resonator as described above. In this case, it is possible to eliminate the noise component. It is more preferable that the aforementioned film is provided on end surfaces of the laser device other than the resonance end surfaces, such as side and bottom surfaces along the resonance direction. In this case, since the luminescent radiation component from the device can be almost completely eliminated, the luminescent radiation does not exist in the laser apparatus. It is possible to improve the precision of detection sensitivity of PD. On the other hand, in the laser device, since the detector is located at the position on which the emitted light or the reflected light (light from the rear-side end surface) is incident, particularly in the case where the aforementioned high reflective protective film is provided at least on the end surface side where the light is incident on the PD, this effect can be obtained. In addition, it is more preferable that the protective films are provided on the both end surfaces of the resonator as main emission outputs for light with high light intensity or density. In this case, it is possible to eliminate almost whole part of the noise component emitted from the laser device.
In a nitride semiconductor laser device according to a third aspect of the present invention, the end surface protective films 110 have a low reflectivity for the wavelength of the emitted light from the active layer 104 .
In this construction, it is possible to provide an end surface protective film that allows resonance of laser light and can suppress outward emission of the luminescent radiation emitted by absorbing stray light.
In a nitride semiconductor laser device according to a fourth aspect of the present invention, the end surface protective films 110 have a single-layer or multilayer structure.
In this construction, it is possible to provide adjustment of a desired reflectivity of the end surface protective film. It is necessary to select a material of the end surface protective film in consideration not only of the reflectivity, refractive index and transmittance, but also of thermal expansion coefficient, stress, and so on. In the case of a multilayer structure, various combinations can provide an end surface protective film with more excellent function.
Furthermore, a nitride semiconductor laser device according to the another aspect of the present invention comprises a nitride semiconductor substrate 101 ; a nitride semiconductor layer that has an n-type semiconductor layer, 102 an active layer 104 and a p-type semiconductor layer 103 laminated on or above the nitride semiconductor substrate 101 , and has a stripe-shaped waveguide region for laser light; and an emission side end surface protective film and a rear-side end surface protective film opposed thereto on the end surfaces substantially perpendicular to the waveguide region. The nitride semiconductor substrate 101 has a luminescent radiation region 112 that absorbs light emitted from the active layer 104 and emits luminescent radiation with a wavelength longer than the wavelength of the emitted light. The rear-side end surface protective film includes a first end surface protective film having a high reflectivity for the wavelength of the luminescent radiation, and a second end surface protective film having a high reflectivity for the wavelength of the emitted light from the active layer 104 . The emission-side end surface protective film includes a third end surface protective film having a high reflectivity for the wavelength of the luminescent radiation. Specifically, as for the reflectivities for the laser light wavelength ? LD and the luminescent radiation wavelength ? ex , this construction includes the first and third end surface protective films having a higher reflectivity for the luminescent radiation wavelength, and the second end surface protective film having a higher reflectivity for the laser light wavelength. That is, this construction has combination of the end surface protective films that have excellent reflectivities for reflection of the laser light and luminescent radiation respectively, and are provided for the end surface protective films to perform functions separated into each of the films.
In this construction, it is possible to suppress outward emission of the luminescent radiation from the rear side. As a result, it is possible to suppress improper operation in the case where a detector (photo diode) is provided on the rear side to perform the driving control, for example. Particularly, the wavelength of the luminescent radiation is longer than the light from the active layer. Accordingly, it is more detectable even if the radiation is weak. FIG. 4 is a spectral sensitivity curve of Si that is a typical photo diode (PD). Its sensitivity peak lies in the infrared region. Thus, light emission with a long wavelength is more detectable. For this reason, in the case of light emission with a relative short wavelength, eg, in proximity of 390 to 420 nm, such as the case of a laser device of a nitride semiconductor, and in the case where luminescent radiation with a wavelength in proximity of 550 to 600 nm is emitted by absorbing the emitted light, the PD sensitivity increases nearly triple. In this case, even light other than laser light is prone to be more detectable, if it is weak. In the case where the light emitted from the rear side is not the luminescent radiation but stray light that is weak light with the same wavelength as the laser light, it is the same light as the laser light in terms of the PD sensitivity. Accordingly, the stray light does not highly affect the PD sensitivity. According to the present invention, stray light is absorbed and converted into luminescent radiation, and the end surface protective film with high reflectivity for the luminescent radiation is formed. Therefore, it is possible to suppress emission of the luminescent radiation from both of the emission side and the rear side, and, as a result, to provide excellent laser device characteristics.
In a nitride semiconductor laser device according to a sixth aspect of the present invention, the first end surface protective film and/or the third end surface protective film has a low reflectivity for the wavelength of the emitted light from the active layer 104 .
In this construction, it is possible to suppress reduction of the reflectivity of the laser light due to the first and third end surface protective films, and, thus, to reduce a threshold.
In a nitride semiconductor laser device according to a seventh aspect of the present invention, the emission-side end surface protective film includes a fourth end surface protective film having a high reflectivity for the wavelength of the emitted light from the active layer 104 . In addition, in a nitride semiconductor laser device according to an eighth aspect of the present invention, each of the first, second, third and fourth end surface protective films 110 has a single-layer or multilayer structure.
In this construction, the reflectivities of the emission side and the rear side can be easily adjusted to desired values. Therefore, it is possible to provide the reflectivities depending on applications.
In a nitride semiconductor laser device according to a ninth aspect of the present invention, the first and second end surface protective films are laminated so as to at least partially overlap each other. In addition, a nitride semiconductor laser device according to a tenth aspect of the present invention, the third and fourth end surface protective films are laminated so as to at least partially overlap each other.
Since the first and second end surface protective films have different wavelengths to reflect light, even in the case of lamination, they can still have high reflectivities for light with target wavelengths, respectively. The third and fourth end surface protective films have a similar effect.
In a nitride semiconductor laser device according to an eleventh aspect of the present invention, the second end surface protective film is formed in contact with the semiconductor layer. In addition, a nitride semiconductor laser device according to a twelfth aspect of the present invention, the fourth end surface protective film is formed in contact with the semiconductor layer.
The luminescent radiation has a wavelength longer than the light emitted from the active layer, and thus has low energy. In addition, since it is excited by stray light that leaks from the waveguide region, its light density is low as compared with the laser light in the waveguide region. Accordingly, in the case where an end surface protective film with a high reflectivity for the light emitted from the active layer is provided in contact with the semiconductor layer, deterioration of the end surface protective film for the luminescent radiation is suppressed. Therefore, it is possible to provide stable mode of laser light.
In a nitride semiconductor laser device according to a thirteen aspect of the present invention, the luminescent radiation region 112 has a low dislocation density as compared with the periphery thereof. Specifically, in a nitride semiconductor substrate having regions with high and low dislocation densities in the substrate plane, the region with the low dislocation density serves as the luminescent radiation region to convert light propagated in the substrate into the luminescent radiation that can be controlled by the aforementioned end surface protective film. As a result, it is possible to prevent emission of the stray light from the laser device.
In a nitride semiconductor laser device according to a fourteenth aspect of the present invention, the luminescent radiation region 112 has a high impurity concentration as compared with the periphery thereof. Specifically, in a nitride semiconductor substrate having regions with high and low impurity concentrations in the substrate plane, the region with the high concentration serves as the luminescent radiation region. In this case, it is possible to enhance the aforementioned structures and effects.
In a nitride semiconductor laser device according to a fifteen aspect of the present invention, the impurity is at least one element selected from the group consisting of H, O, C and Si.
In a nitride semiconductor laser device according to a sixteen aspect of the present invention, the active layer 104 has a light emission wavelength of 390 to 420 nm.
In a nitride semiconductor laser device according to a seventeen aspect of the present invention, the luminescent radiation has aa wavelength of 550 to 600 nm.
In a nitride semiconductor laser device according to an eighteen aspect of the present invention, the luminescent radiation region 112 is formed in a stripe shape substantially parallel to the waveguide region. Specifically, the aforementioned high impurity region or low dislocation density region in the substrate plane is formed in a stripe shape as the luminescent radiation region, and is arranged such that the stripe direction is substantially parallel to the stripe direction of a ridge stripe as the waveguide. In this parallel arrangement, light leaks in the vertical and transverse directions from the stripe-shaped waveguide region as a source serves as light to be converted into the luminescent radiation. As a result, the arrangement of the waveguide region and the luminescent radiation region parallel to each other suitably provides the aforementioned light conversion and luminescent radiation.
In a nitride semiconductor laser device according to a nineteenth aspect of the present invention, the waveguide region is formed above the luminescent radiation region 112 . Specifically, the waveguide region of the semiconductor layer is provided such that the aforementioned high impurity region or low dislocation density region as the luminescent radiation region at least partially overlaps the region in the substrate plane. It is preferable that the luminescent radiation region covers almost the whole waveguide region. In the case where the whole laser construction has a ridge waveguide structure, in order to be overlapped the stripe-shaped ridge in the substrate plane, it is preferable that the luminescent radiation region with a width wider than the ridge stripe overlaps the ridge. In this case, it is possible to provide efficient luminescent radiation and light conversion of stray light.
In a nitride semiconductor laser device according to a twentieth aspect of the present invention, the waveguide region is formed in a region that is spaced away from the luminescent radiation region 112 . Specifically, the luminescent radiation region and the waveguide region of the laser device structure on the substrate are spaced away from each other. In the case where the luminescent radiation region and the waveguide region have stripe shapes, a structure having the stripe shapes that extend along substantially the same longitudinal direction in parallel to each other can be given as an example.
A laser apparatus according to a twenty-first aspect of the present invention comprises the aforementioned nitride semiconductor laser device, and a detector of PD (photo diode) that detect the laser light. The PD has a spectral sensitivity in a luminescent radiation wavelength ? ex higher than a laser light wavelength ? LD . In other words, the laser apparatus includes a photo diode with a spectrum sensitivity of [sensitivity for ? LD ]<[sensitivity for ? ex ] as the detector. In the laser apparatus having PD with a high sensitivity for luminescent radiation, even if small leakage of luminescent radiation seriously affect a laser apparatus, confinement of luminescent radiation by the aforementioned end surface protective film properly functions, and thus can provide precise control of LD driving. Since a Si semiconductor typically used as a photodiode is not a PD less sensitive for a wavelength region of a wide band gap nitride semiconductor laser device, it is difficult to precisely control the nitride semiconductor laser device in a laser apparatus using the PD as a detector. However, the present invention can solve this problem. In reference to the laser apparatus, specifically, there is a CAN type laser apparatus having a laser device chip and a PD chip that are mounted on mount portions, respectively, and are connected to terminals in the laser apparatus by wires, and so on. In addition to this CAN type laser device apparatus, there is a laser apparatus having an integrated laser coupler with a laser device chip, a PD chip and a circuit that drives them and provides external terminals. As for a laser coupler, there is a laser apparatus composed of a stuck device that has a laser device chip and a PD chip laminated and mounted thereon, and an additional mount substrate and a base body that are provided with the laser device side and the PD chip side mounted thereon, respectively. Laser devices, in this case, are not limited to only one type of the aforementioned nitride semiconductor laser device, but can include second laser device that emits laser light with different wavelength. That is, this type of laser apparatus can be a multi-wavelength laser apparatus with a plurality of laser devices.
A nitride laser semiconductor laser device according to the present invention absorbs stray light inside the substrate, and thus suppresses FFP deterioration due to mixture of the stray light into laser light. In addition, the laser device absorbs the stray light and emits luminescent radiation, and has a high reflective end surface protective film formed therein such that the luminescent radiation is not emitted outward. Therefore, the laser device can provide more stable laser light. Furthermore, a high reflective end surface protective film is also formed on the rear side to prevent improper operation of a detector due to the luminescent radiation with a wavelength longer than light emitted from the active layer, thus, precise driving control can be obtained. Therefore, it is possible to provide an excellent reliable semiconductor laser device.
BREVE DESCRIPCIÓN DE LOS DIBUJOS
FIG. 1( a ) is a schematic perspective view for explanation of a semiconductor laser device according to the present invention;
FIG. 1( b ) is a cross-sectional view of FIG. 1( a ) along a line bb?;
FIG. 1( c ) is a cross-sectional view of FIG. 1( a ) along a line cc?;
FIG. 2 is a graph showing the transmittance of an end surface protective film according to an embodiment of the present invention;
FIG. 3 is a graph showing the transmittance of an end surface protective film according to the embodiment of the present invention; and
FIG. 4 is a spectral sensitivity curve of a photodiode.
DESCRIPCIÓN DETALLADA DE LAS MODALIDADES PREFERIDAS
The following description will describe a nitride semiconductor laser device according to the present invention, however, the present invention is not limited to a device structure shown in embodiments.
The nitride semiconductor laser device according to the present invention includes a nitride semiconductor substrate having a luminescent radiation region that absorbs light emitted from an active layer and emits luminescent radiation with a wavelength longer than the wavelength of the emitted light, and thus suppresses outward emission of light (stray light) that leaks from a laser light waveguide region. This can provide suitable device characteristics.
FIG. 1 shows the construction of the nitride semiconductor laser device according to this embodiment. The nitride semiconductor laser device according to the present invention includes an n-type nitride semiconductor layer 102 , an active layer 104 and a p-type nitride semiconductor layer 103 that are laminated on a nitride semiconductor substrate 101 . The p-type nitride semiconductor layer is provided with a stripe-shaped ridge. The ridge can be formed by removing a part of the p-type nitride semiconductor layer in an etching method, and so on, and thus provides an effective refraction type waveguide. In addition, the ridge may be formed to provide a refraction type waveguide by etching a part of the p-type to n-type nitride semiconductor layers. Alternatively, the ridge may be formed in a selective growing method. The ridge is not limited to a normal mesa shape with wide stripe width on the bottom side and decreasing as closer to the top. The ridge may be an inverse mesa shape with width decreasing as closer to the ridge bottom. In addition, the ridge may be a stripe with side surfaces perpendicular to the lamination plane, or may be a shape of combination of them. It is not necessary that a stripe-shaped waveguide has a substantially constant width. Furthermore, a buried type laser having semiconductor layers that are formed on the ridge surface and beside the ridge after the ridge is formed may be used. Moreover, a gain waveguide type laser without ridge may be used.
A first insulating film 109 is formed on the side surface of the ridge and the top surface of the p-type nitride semiconductor layer contiguous to the ridge. A p-side ohmic electrode 105 is provided on the top surfaces of the ridge and the first insulating film. An n-side ohmic electrode 107 is provided on the back surface of the nitride semiconductor substrate. A second insulating film 108 that covers the side surfaces of the semiconductor layer is continuously provided to the upper part of the first insulating film. A p-side pad electrode 106 in contact with the second insulating film and the p-side ohmic electrode is provided on the upper part of the p-type nitride semiconductor layer.
(Nitride Semiconductor Substrate)
GaN, AlN and InN, and a mixture crystal of them as AlGaN group. InGaN group and AlInGaN group can be given as the composition of the substrate to be used. The substrate can be produced as follows.
A nitride semiconductor with a thickness of 100 ?m or more is thickly grown on a different material substrate by a hydride vapor-phase-epitaxy method (hereinafter referred to as a HVPE method). After that, the different material substrate is removed, thus, the nitride semiconductor as the substrate can be provided. The surface of the nitride semiconductor after the substrate is removed is (000 1 ) plane. Inclined surfaces other than (000 1 ) plane are formed by dry etching, wet etching or chemical-mechanical polishing (hereinafter, referred to as CMP). In the case where the half-value width of the nitride semiconductor of a (0002) diffraction X-ray rocking curve in a biaxial crystal method is three minute or less, preferably two minutes or less, the nitride semiconductor is less prone to be damaged even in a process for removing the different substrate. Accordingly, it is possible to provide a nitride semiconductor with a thickness of 100 ?m or more that retains excellent crystallinity. Subsequently, a new nitride semiconductor element is formed on (0001) plane of the nitride semiconductor. In addition, a first electrode is formed on the back surface of the nitride semiconductor.
El semiconductor de nitruro está representado por una fórmula general de In x Al y Ga 1-XY N (0 ? X ? 1, 0 ? Y ? 1, 0 ? X + Y ? 1). The nitride semiconductor is preferably formed above the different material substrate so as to interpose a buffer layer represented by Al a Ga 1-a N (0.01<a?0.5) between them. The reason is to improve its crystallinity. The buffer layer is grown at a low growth temperature of 800° C. or less. This growth can reduce dislocation and pits in the nitride semiconductor. After the buffer layer is grown on the different material substrate by a metal-organic chemical vapor deposition method (hereinafter, referred to as a MOCVD method), a layer of Al X Ga 1-X N (0?X?1) may be additionally grown by an epitaxially lateral overgrowth method (ELO method). The ELO method laterally grows a nitride semiconductor to bend threading dislocation, an additionally to converge the threading dislocation. This reduces the threading dislocation on the surface side, and thus improves its crystallinity.
Various substrates, such as GaAs substrate, sapphire substrate, SiC substrate, Si substrate, spinel substrate, NdGaO 3 substrate, ZnO substrate, GaP substrate and GaN substrate, and so on, can be sued as a growth substrate for growing the nitride semiconductor substrate.
In the case the nitride semiconductor layer is grown by a growth method that laterally grows the layer as described above, and is used as the substrate, it is possible to provide a substrate in which the dislocation density (defect density), or the like, are not uniform in a location corresponding to a shape of the growth starting point. In addition, it is preferable that the layer is grown while an impurity is doped. In this case, a region with non-uniform impurity concentration is also formed so as to correspond the distribution state of the aforementioned dislocation density.
As for a low dislocation density region as described above, its distribution state can be selected by the shape of the growth starting point. Since the laser light waveguide region is formed in a stripe shape, the growth starting point is preferably formed in a stripe shape corresponding to it. In the case where a nitride semiconductor layer is grown from growth starting points that are cyclically arranged in a stripe shape, it is possible to provide a nitride semiconductor substrate that cyclically is provided with a region that has a low dislocation density and excellent crystallinity, and, on the other hand, a region that has much dislocation and poor crystallinity (dislocation flux). A nitride semiconductor layer is less prone to grow on the dislocation flux. Such a nitride semiconductor layer grown thereon has poor crystallinity. For this reason, it is prone to affect adversely when the device is driven. Accordingly, it is preferable that an operation region such as a waveguide region is formed in a region other than the dislocation flux. For example, deterioration of the device characteristics can be suppressed by adjustment of the region to be located in proximity of the device division position, as shown in FIG. 1( b ).
The nitride semiconductor substrate is formed to be conductive by doping an impurity. In this case, an n-electrode can be provided on the substrate back surface side, as shown in FIG. 1. The substrate can be an insulating or low conductive substrate. In this case, the n-electrode is provided on the same plane side as a p-electrode 105 . In terms of strength, and so on, in handling, the nitride semiconductor substrate preferably has a thickness of approximately 100 ?m.
(Luminescent Radiation Region)
The nitride semiconductor substrate that is grown on the growth substrate as described above includes a region where it is laterally grown. Accordingly, its crystal characteristics are less prone to be uniform in the plane. For this reason, regions with different dislocation densities and impurity concentrations are formed. Particularly, since the region with a low dislocation density tends to absorb the wavelength of light emitted from the active layer as compared with the region with a high density, it serves as the luminescent radiation region. Depending on the type of employed growth substrate, the growth condition of nitride semiconductor layer (temperature, gas flow rate, pressure, and type and concentration of impurity), and so on, the state of the formed luminescent region varies. Accordingly, the boundary between the luminescent radiation region and a non-luminescent radiation region is not clear. A luminescent radiation region that emits low luminescent radiation in almost the whole surface can be formed. On the other hand, a luminescent radiation region 112 that locally emits high luminescent radiation as shown in FIG. 1( b ) can be formed. A preferable form of these types can be selected depending on the purpose and application. The shape and distribution of the luminescent radiation of the substrate depends on the type and growth condition of the aforementioned substrate.
In addition, it is preferable that the luminescent radiation region is formed so as to correspond to the laser light waveguide region, specifically, such that the luminescent radiation region and the waveguide region or the ridge stripe overlap each other in the substrate plane.
Additionally, in the case where the waveguide region is formed in the nitride semiconductor layer that is grown on the luminescent radiation region, it is possible to provide an excellent waveguide region for laser light. In the case where the luminescent radiation region is formed in the location corresponding to the waveguide region, it is possible to improve the absorption efficiency of stray light. For this reason, the luminescent radiation region is preferably provided in proximity to the waveguide region. However, too much absorption may cause threshold to increase. In this case, the waveguide region is spaced away from the luminescent radiation region, specifically, the luminescent radiation region and the waveguide region or the ridge stripe are spaced away from each other. Thus, the waveguide region can be formed in a grown nitride semiconductor. The luminescent radiation region is only required to be able to absorb the wavelength of light emitted from the active layer and to emit luminescent radiation. Specifically, the luminescent radiation region is only required to provide high luminescent radiation as compared with a partial region other than the luminescent radiation region. Accordingly, in addition to adjustment of dislocation density or impurity by the aforementioned nitride semiconductor substrate growth method, the luminescent radiation region can be formed by ion implantation, or the like, in the later processes.
(End Surface Protective Film 110 )
In the present invention, the end surface protective films have a high reflectivity for the wavelength of the luminescent radiation from the luminescent radiation region. The end surface protective film can have a single-layer or multilayer structure. Since the luminescent radiation is emitted by absorbing stray light that leaks from the waveguide region, its intensity is low as compared with laser light outwardly emitted from the waveguide region. For this reason, it is preferable that its reflectivity is set to a certain degree that does not prevent laser light emission. Its thickness is preferably small. The reason is that, although the laser light is less prone to be reflected due to the wavelength difference, it may be absorbed in the case of some materials. In addition, although the laser light passes the end surface protective film, the end surface protective film causes loss more or less.
The end surface protective film is provided with not only an end surface protective film for the wavelength of the luminescent radiation, but also an end surface protective film for the wavelength of laser light. Accordingly, it is possible to efficiently emit laser light. The rear-side end surface protective film includes a first end surface protective film having a high reflectivity for the wavelength of the luminescent radiation, and a second end surface protective film having a high reflectivity for the wavelength of the emitted light from the waveguide region. In addition, the emission-side end surface protective film includes a third end surface protective film having a high reflectivity for the wavelength of the luminescent radiation, and a fourth end surface protective film having a high reflectivity for the wavelength of the emitted light from the active layer.
Although either of the first and second end surface protective films can be contact with the semiconductor layer, it is preferable that the second end surface protective film is in contact with the semiconductor layer. In this case, it is possible to suppress deterioration of the first end surface protective film.
In the case where the third end surface protective film is only provided on the emission-side end surface, its thickness is set to a high reflectivity for the wavelength of the luminescent radiation, and the film with the set thickness is provided on the whole emission-side end surface. Although the third end surface protective film is required to be provided only a region where the luminescent radiation is emitted outward, it is provided the end surface to serve as a protective film that prevents the exposure of the semiconductor layer including the active layer, and so on, to air. Since the luminescent radiation and the laser light have different wavelengths, the laser light is less prone to be cut off. Specifically, in the case where the luminescent radiation region and the waveguide region corresponds to each other as described above, it is preferable that the protective film is provided so as to cover the luminescent radiation region on the substrate end surface, more preferably to cover, in the substrate and the device structure located thereon, the luminescent radiation region of the substrate and the waveguide region on the end surface of the device structure including the active layer.
In addition to the third end surface protective film, the fourth end surface protective film can be provided on the emission-side end surface. In this case, when the fourth end surface protective film is in contact with the semiconductor layer, it is possible to suppress deterioration of the third end surface protective film due to the laser light with high light density. In addition, adjustment of reflectivity by the protective film disposed on the emission side can provide efficient laser light emission, and thus can reduce the threshold. The luminescent radiation is not reflected by the fourth protective film and passes the fourth protective film. It is reflected by the first protective film, and thus does not outgo.
Specifically, at least one conductive material selected from the group consisting of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B, Ti, and a compound such as oxides, nitride and fluoride of them can be employed as a material of the end surface protective film. Only one material of them can be employed. Alternatively, a plurality of materials among them can be employed as a compound or multi layers. A material employing Si, Mg, Al, Hf, Zr, Y, or Ga is preferable. In addition, a semiconductor material such as AlN, AlGaN and BN can be employed. As for an insulating material, a compound, such as oxide, the nitride and fluoride of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y and B, can be employed.
The following combinations can be given as preferable materials of the first to fourth end surface protective films, for example.
A: First End Surface Protective Film (Rear-Side End Surface Protective Film for Luminescent Radiation)
GaN/ZrO 2 +one to three pair(s) of (SiO 2 /ZrO 2 )
GaN/TiO 2 +one to three pair(s) of (SiO 2 /TiO 2 )
B: Second End Surface Protective Film (Rear-Side End Surface Protective Film for Light Emission of Active Layer)
GaN/ZrO 2 +three to six pairs of (SiO 2 /ZrO 2 )
GaN/TiO 2 +three to six pairs of (SiO 2 /TiO 2 )
C: Third End Surface Protective Film (Emission-Side End Surface Protective Film for Luminescent Radiation)
GaN/one or two pair(s) of (SiO 2 /Nb 2 O 5 )
GaN/one or two pair(s) of (Al 2 O 3 /Nb 2 O 5 )
GaN/one or two pair(s) of (Al 2 O 3 /TiO 2 )
GaN/Al 2 O 3 +one or three pair(s) of (SiO 2 /Nb 2 O 5 )
D: Fourth End Surface Protective Film (Emission-Side End Surface Protective Film for Light Emission of Active Layer)
GaN/ZrO 2 +one to three pair(s) of (SiO 2 /ZrO 2 )
GaN/TiO 2 +one to three pair(s) of (SiO 2 /TiO 2 )
In the aforementioned combinations, thickness adjustment depending on the wavelengths can provide a laser device with excellent characteristics.
(Electrode)
A material having good ohmic characteristics and bonding characteristics for the p-type nitride semiconductor layer can be employed as an electrode material of the p-side ohmic electrode that is provided on the p-type nitride semiconductor layer. Specifically, Ni, Co, Fe, Cr, Al, Cu, Au, W, Mo, Ta, Ag, Pt, Pd, Rh, Ir, Ru, Os, and oxide and nitride of them can be given as the examples. A single layer, alloy or multi layers of them can be used. At least one element selected from the group consisting of Ni, Co, Fe, Cu, Au and Al, and oxide and nitride of them are preferable.
Thermal treatment can provide excellent ohmic characteristics of the p-side ohmic electrode. The thermal treatment temperature is preferably in the range of 350° C. to 1200° C., more preferably 400° C. to 750° C., and most preferably 500° C. to 650° C.
Además, Ni, Co, Fe, Ti, Cu, Au, W, Mo, Zr, Ta, Ag, Pt, Pd, Rh, Ir, Ru, Os, y el óxido y el nitruro de ellos se pueden dar como ejemplos de el p-pad electrodo lateral 106. Una sola capa, o de múltiples capas de aleación de ellos pueden ser utilizados. Dado que la capa superior del mismo está conectado al cable, o similares, preferentemente Au es empleado como la capa superior. A fin de evitar la difusión de Au, un material con un punto de fusión relativamente alto es preferentemente utilizado como una capa inferior para servir como una capa de prevención de la difusión. Por ejemplo, Ti, Pt, W, Ta, Mo, TiN, etc, se puede dar como ejemplo. En particular, Ti puede ser dado como un material preferible. En cuanto a espesor, el espesor total es de preferencia en el rango de 3000 a 20000 ? ?, más preferiblemente ? 7000 a 13000 ?.
En cuanto a la N-electrodo que se proporciona en la N-semiconductor de nitruro de tipo, en caso de que el sustrato de semiconductor de nitruro es conductor, es preferible siempre en la superficie posterior del sustrato. Alternativamente, puede formarse en una superficie expuesta por el grabado, o por el estilo. Además, pueden formarse en una n-capa de contacto de tipo. En el caso de que se proporciona en el lado mismo plano que el p-electrodo, el electrodo óhmico y el electrodo almohadilla se puede formar en el mismo proceso o procesos diferentes. Además, el tratamiento térmico puede omitirse en el caso de algunos materiales.
Un material con buenas características óhmicas y las características de unión de la N-Type nitruro de capa de semiconductor puede ser empleado como material de los electrodos de la N-electrodo lateral óhmica. En concreto, Ni, Co, Fe, Ti, Cu, Au, W, V, Zr, Mo, Ta, Al, Ag, Pt, Pd, Rh, Ir, Ru, Os, y así sucesivamente, se puede administrar como los ejemplos . Una sola capa, o de múltiples capas de aleación de ellos pueden ser utilizados. Una estructura de múltiples capas de Ti y Al que son sucesivamente laminado se utiliza preferentemente. A fin de ofrecer buenas características óhmico para la capa de semiconductores, después de la N-electrodo lado óhmico se forma, el tratamiento térmico se realiza preferiblemente en el caso de algunos materiales. En cuanto al espesor de la N-electrodo lateral óhmico, el grueso total es de preferencia cerca de 100 ? a 30000 ?, más preferiblemente 3000 ? ? a 15000, y más preferiblemente 5000 ? a 10000 ?. Es preferible que la N-electrodo lateral óhmico se forma dentro de la gama. La razón es que un electrodo con una baja resistencia de contacto se puede proporcionar en este caso.
Además, Ni, Co, Fe, Ti, Cu, Au, W, Zr, Mo, Ta, Al, Ag, Pt, Pd, Rh, Ir, Ru, Os, y así sucesivamente, se puede administrar como los ejemplos de la N-pad electrodo lateral. Una sola capa, o de múltiples capas de aleación de ellos pueden ser utilizados. El n-pad electrodo lateral de preferencia tiene una estructura de múltiples capas. Dado que la capa superior del mismo está conectado al cable, o similares, preferentemente Au es empleado como la capa superior. A fin de evitar la difusión de Au, un material con un punto de fusión relativamente alto es preferentemente utilizado como una capa inferior para servir como una capa de prevención de la difusión. Por ejemplo, Ti, Pt, W, Mo, TiN, etc, se puede administrar como los ejemplos. En cuanto a espesor, el espesor total es de preferencia en el rango de 3000 a 20000 ? ?, más preferiblemente ? 7000 a 13000 ?.
El n-electrodo lateral no podrá ser formado de manera similar al electrodo óhmico y la almohadilla de electrodo formado en diferentes procesos como se describió anteriormente, pero puede ser continua y han formado ambas funciones. Es decir, la N-electrodo puede sirve como un electrodo óhmicas en contacto óhmico con la capa de semiconductor y un archivo adjunto de electrodos (electrodo PAD) que está conectado al cable. La razón es que la N-electrodo secundarios relativamente pueden fácilmente proporcionar contacto óhmico para la n-capas de semiconductores tipo en comparación con el P-electrodo lateral. Además, desde que se forma en una región de espacio fuera de la región de guía de ondas en una pequeña parte, no es muy necesario tener en sus características visuales en consideración. Por lo tanto, tiene la flexibilidad en el material. En cuanto al espesor de la N-electrodo, el espesor total es de preferencia en el rango de 3000 a 20000 ? ?, más preferiblemente ? 7000 a 13000 ?. Ti / Al, HF / Al, Ti / Pt / Au, Ti / Mes / Pt / Au, Ti / Mes / Ti / Pt / Au, Ti / W / Pt / Au, Ti / W / Ti / Pt / Au, Mo / Pt / Au, Mo / Ti / Pt / Au, W / Pt / Au, V / Pt / Au, V / Mo / Pt / Au, V / W / Pt / Au, Cr / Pt / Au, Cr / Mo / Pt / Au, Cr / W / Pt / Au, y así sucesivamente, se puede administrar como combinaciones preferible. En el caso de que la N-electrodo se forma en el sustrato de la superficie posterior, una corriente que puede ser aplicada por la vinculación con Au / Sn.
La primera película aislante se presta para limitar una región de inyección de corriente a la cresta superficie superior. Sin embargo, desde la primera película aislante está situado en la proximidad de la región de guía de ondas, tiene un efecto sobre la eficiencia de confinamiento de luz. Un grosor preferible de la primera película aislante se puede seleccionar en función de un material de película aislante que se utilizará. La primera película aislante se puede formar con el fin de tener apreciablemente la misma anchura que la capa de semiconductor de nitruro. La primera capa aislante que se forma antes de la p-electrodo lado óhmico es sometido al tratamiento térmico, junto con el electrodo óhmicas en el proceso de tratamiento térmico para el electrodo óhmica. El tratamiento térmico aumenta la resistencia de la película (atómico-fuerza de enlace a nivel de la película), en comparación con una película como depósito, y por lo tanto mejora la intensidad de la unión en la interfase con la capa de semiconductor en el medio. En particular, en el caso de que este tipo de película aislante primero está formado hasta el final de la capa de semiconductor superficie superior, donde la película aislante segundos se forma, es posible mejorar las características de unión de la segunda película aislante.
Además, la plataforma P-electrodo secundarios pueden ser formados de manera que no estar en contacto con la película aislante segundo. En particular, en el caso de las uniones por adhesión, el calor es conducido a la categoría P-pad electrodo lateral. En este momento, su volumen aumenta debido a la expansión térmica, por lo tanto, tiende a moverse hacia la superficie lateral del dispositivo (hacia el final de la categoría P-capa de semiconductor tipo). Además, no sólo el calor, pero también se aplica la presión, por lo tanto, el material del electrodo tiende a moverse hacia la superficie lateral. En el caso de que la plataforma P-electrodo de lado es el espacio fuera de la película aislante en segundo lugar, es posible evitar un cortocircuito, debido al traslado del material del electrodo de la plataforma P-electrodo lateral hacia la superficie lateral.
La película aislante primero es preferentemente formado por un material de óxido que contiene al menos un elemento seleccionado del grupo formado por Si, Ti, V, Zr, Nb, Hf y Ta, o por lo menos un material seleccionado entre el grupo formado SiN, BN, SiC, AlN y Algan, y más preferiblemente de un óxido de Zr, Hf o Si, o BN, AlN o Algan entre ellos.
En concreto, el espesor de la capa aislante de primera se establece en el rango entre no menos de 10 ni más ? 10000 ?, y preferiblemente entre no menos de 100 ? y no más de 5000 ?. La razón es que, si es menor de 10 ?, es difícil garantizar el suficiente aislamiento, cuando se forme el electrodo. Por otro lado, si es más de 10000 ?, la película de protección no es uniforme, por lo tanto, una película aislante excelente, no puede siempre. Además, en el caso de que el espesor cae dentro del rango anterior, una película uniforme con la diferencia de un excelente índice de refracción entre la película y la cresta se forma en el lado de cresta superficies.
La superficie de aislamiento segundo puede ser proporcionada en toda la superficie de la P-electrodo lateral óhmico a excepción de la cresta superficie superior. Además, es preferible que la película aislante segundo es prestado de manera continua la superficie del extremo lateral de la P-capa de semiconductor tipo y la capa activa expuesta por el grabado. La película está formada preferiblemente de un material de óxido que contiene al menos un elemento seleccionado del grupo formado por Si, Ti, V, Zr, Nb, Hf y Ta, o por lo menos un material seleccionado entre el grupo formado SiN, BN, SiC, ALN y Algan. La película una sola capa o película de múltiples capas de SiO 2, Al 2 O 3, ZrO 2 y TiO 2 puede ser dado como un material más preferible entre ellos.
Furthermore, a pair of resonance surfaces that are provided on the end surfaces to specify the resonance direction along the stripe direction of the aforementioned ridge can be formed by cleavage, etching, or the like. In the case where the resonance surfaces are formed by cleavage, the substrate and the semiconductor layer preferably have cleavage characteristics. An excellent mirror surface can be obtained by using the cleavage characteristics. In addition, in the case where they do not have the cleavage characteristics, the resonance surfaces can be formed by etching. In this case, the resonance surfaces are formed in the same process as exposure of the n-electrode formation surface, and thus can be provided by fewer processes. Additionally, they can be formed in the same process as the ridge formation. Although the formation of them in the same process as other process as described above can reduce the number of processes, a separated process for the formation of resonance surfaces is preferably included in order to provide a more excellent resonance surfaces.
Specifically, in the case where the resonance surfaces are etched end surfaces, for example, after the etched end surfaces are formed, the high reflective (second and fourth) end surface protective films for laser light are provided on the end surfaces (emission and reflection sides), then the substrate is cleaved such that the wafer is divided into bar-shaped elements as described later. After that, the high reflective (first and third) end surface protective films for luminescent radiation are formed so as to cover the exposed substrate end surfaces and the etched surfaces. In this case, the etched end surface and the substrate end surface can have different film structures (different numbers of layers, where the end surface is for both the laser light and luminescent radiation, and the substrate end surface is for luminescent radiation).
EJEMPLO 1
The following description will describe examples. However, a device structure of the n-type nitride semiconductor layer, active layer and p-type nitride semiconductor layer that compose the nitride semiconductor layer according to the present invention is not specifically limited to them, various lamination structure can be used. Laser device structures described in the following examples can be used, however, other device structures can be applied. A III-V nitride semiconductor group semiconductor including a nitride semiconductor such as GaN, AlN and InN, and a mixture crystal of them can be employed. Additionally, A III-V nitride semiconductor group semiconductor containing B, P, and so on, can be used. Any known methods that grows a nitride semiconductor, such as MOVPE, MOCVD (metalorganic chemical vapor deposition), HVPE (halide vapor-phase epitaxiay), MBE (molecular beam epitaxy), and so on, can be used for growth of the nitride semiconductor.
(Nitride Semiconductor Substrate)
First, a 2-inch different material substrate of sapphire having C-plane as primary surface is set in a MOCVD reactor vessel. A buffer layer of GaN with a thickness of 200 ? is grown thereon at temperature of 500° C. by using trimethyl gallium (TMG), and ammonia (NH3). In addition, a foundation layer of GaN with a thickness of 2.5 ?m is grown at temperature of 1000° C. or more. After that, it is moved to a HVPE reactor vessel. A nitride semiconductor of GaN with a thickness of 500 ?m is grown by using Ga metal, HCl gas and ammonia as materials. Subsequently, only the sapphire is peeled off by excimer laser irradiation, and a nitride semiconductor with a thickness of 450 ?m is formed by performing CMP.
(N-Type Contact Layer)
An n-type contact layer of Si-doped n-Al 0.02 Ga 0.98 N with a thickness of 3.5 ?m is grown at 1050° C. similarly by using TMG and ammonia gas as source gases, and a silane gas as an impurity gas. The thickness of the n-type contact layer is not limited as long as it falls within the range 2 to 30 ?m.
(Clack Prevention Layer)
Subsequently, a clack prevention layer of Si-doped n-In 0.05 Ga 0.95 N with a thickness of 0.15 ?m is grown at 800° C. by using TMG, TMI (trimethyl indium) and ammonia.
In addition, in the case where the nitride semiconductor substrate is a conductive substrate and is provided an n-electrode that is formed on the back surface of the substrate after a substrate for growth is removed, it is possible to start laminating the following n-type cladding layer on the nitride semiconductor substrate.
(N-Type Cladding Layer)
Subsequently, a layer A of undoped Al 0.05 Ga 0.095 N and a layer B of Si-doped GaN with the same thickness of 50 ? are grown at temperature of 1050° C. by using TMA (trimethyl aluminum), TMG and ammonia as source gases. These formation steps are repeated 110 times each to alternately laminate the layers A and B, thus, the n-type cladding layer of multilayer film (superlattice structure) with the total thickness of 1.1 ?m is grown. In this case, when the mixture ratio of Al in the unoped AlGaN falls within the range between not less than 0.02 and not more than 0.3, it is possible to obtain the sufficient refractive index difference that provide the function of cladding layer, and even a single layer structure can be formed.
(N-Type Light Guide Layer)
Subsequently, an n-type light guide layer of undoped GaN with a thickness of 0.15 ?m is grown at a similar temperature by using TMG and ammonia as source gases. An n-type impurity may be doped in this layer.
(Active Layer)
Subsequently, a barrier layer of Si-doped In 0.02 Ga 0.98 N with a thickness of 140 ? is grown at temperature of 800° C. by using TMI (trimethyl indium), TMG and ammonia as source gases, and a silane gas as an impurity gas. Then, the silane gas is stopped, and a well layer of undoped In 0.1 Ga 0.9 N with a thickness of 70 ? is grown. These formation steps are repeated twice each, and then the barrier layer of Si-doped In 0.02 Ga 0.98 N with a thickness of 140 ? is finally grown. Thus, an active layer of multiquantum well structure (MQW) with the total thickness of 560 ? is grown.
(P-Type Electron Confinement Layer)
A p-type electron confinement layer of Mg-doped Al 0.25 Ga 0.75 N with a thickness of 30 ? is grown at a similar temperature under a N 2 atmosphere. Subsequently, another p-type electron confinement layer of Mg-doped Al 0.25 Ga 0.75 N with a thickness of 70 ? is grown under a H 2 atmosphere.
(P-Type Light Guide Layer)
Subsequently, a p-type light guide layer of undoped GaN with a thickness of 0.15 ?m is grown at temperature of 1050° C. by using TMG and ammonia as source gases. This p-type light guide layer is grown as an undoped layer, however, Mg may be doped therein.
(P-Type Cladding Layer)
Subsequently, a layer A of undoped Al 0.08 Ga 0.92 N with a thickness of 80 ? is grown, and a layer B of Mg-doped GaN with a thickness of 80 ? is grown thereon. These formation steps are repeated 28 times each to alternately laminate the layers A and B, thus, the p-type cladding layer of multilayer film (superlattice structure) with the total thickness of 0.45 ?m is grown. In the case where the p-type cladding layer is formed in a superlattice structure that has laminated nitride semiconductor layers with band gaps different from each other at least one of which is a semiconductor layer containing Al, when any one of them has a doped impurity concentration higher than the other, in other words, when modulation doping is performed, their crystallinity tends to be better. However, they may have the same doped impurity concentration.
(P-Type Contact Layer)
Finally, a p-type contact layer of Mg-doped GaN with a thickness of 150 ? is grown at 1050° C. on the p-type cladding layer. The p-type contact layer can be formed of p-type In x Al y Ga 1-xy N (0?x, 0?y, x+y?1). It is preferably formed of Mg-doped GaN. The reason is that, in this case, the most preferable ohmic contact can be obtained. After reaction, the wafer is annealed at 700° C. under a nitrogen atmosphere in a reactor vessel to reduce resistance of the p-type layers.
(Exposure of N-Type Layer)
After the nitride semiconductor layers are grown and thus compose the lamination structure as described above, the wafer is moved from the reactor vessel. A protective film of SiO 2 is formed on the surface of the p-type contact layer as the top layer. The surface of the n-type contact layer is etched to be exposed by RIE (reactive ion etching) with a Cl 2 gas. In addition, resonance surfaces may be formed in this process. Additionally, in the case where the n-electrode is provided on the back surface of the substrate as shown in a later-described example 3, the n-electrode formation surface is not required. Accordingly, this process can be eliminated.
(Ridge Formation)
Subsequently, in order to form a stripe shaped waveguide region, after a protective film of Si oxide (mainly SiO 2 ) with a thickness of 0.5 ?m is formed on almost the whole p-type contact layer as the to player by a CVD device, a mask with a prescribed shape is formed on the protective film by a photolithography technique. A RIE device etches it with a CHF 3 gas, and thus the stripe-shaped protective film of Si oxide is formed. This protective film of Si oxide serves as a mask, and the semiconductor layers are etched with a SiCl 4 gas, thus, the ridge stripe is formed above the active layer. In this case, the ridge has a width of 1.6 ?m.
(First Insulating Film)
In the state where the SiO 2 mask is formed, a first insulating film of ZrO 2 with a thickness of 550 ? is formed on the p-type semiconductor layer. The first insulating film can be provided on the whole semiconductor layer after an n-side ohmic electrode formation surface is masked. In addition, in order to easily divide the wafer, a portion where the insulating film is not formed may be provided.
After the first insulating film is formed, thermal treatment is performed on the wafer at 600° C. In the case where the first insulating film of a material other than SiO 2 is formed as described above, after the first insulating film is formed, the thermal treatment is performed in the range between not less than 300° C., preferably not less than 400° C. and not more than a decomposition temperature of nitride semiconductor (1200° C.), thus, the insulating material can be stable. Particularly, in the case where device processing is performed by mainly using SiO 2 as a mask in a process after the first insulating film is formed, the first insulating film can provide resistance for dissolution against a material for dissolving the mask used in a process the SiO 2 mask is removed. The thermal treatment process of the first insulating film can be eliminated depending on materials and processes of the first insulating film. In addition, the process order, and so on, can be suitably selected. For example, the thermal treatment process can be performed in the same process as thermal treatment of the ohmic electrode. After thermal treatment, the wafer is soaked in a buffered solution to dissolve and remove SiO 2 formed on the top surface of the ridge stripe. ZrO 2 on the p-type contact layer (additionally, on the n-type contact layer) is removed together with SiO 2 by a lift-off method. Thus, the top surface of the ridge is exposed, and the side surfaces of the ridge are covered with ZrO 2 .
(Ohmic Electrode)
Subsequently, a p-side ohmic electrode is formed on the top surface of the p-type contact layer and the first insulating film by sputtering. Ni/Au (100 ?/1500 ?) is employed as the p-side ohmic electrode. In addition, the n-side ohmic electrode is formed on the top surface of the n-type contact surface. The n-side ohmic electrode is composed of Ti/Al (200 ?/5500 ?), and is formed in a stripe shape in parallel to the ridge with a length similar to the ridge. After these electrodes are formed, thermal treatment is performed at 600° C. under a mixture atmosphere of oxygen and nitrogen.
(Second Insulating Film)
Subsequently, a resist is formed so as to cover on the whole surface of the p-side ohmic electrode on the ridge and a part of the upper surface of the n-side ohmic electrode. Then, a second insulating film of SiO 2 is formed on almost the whole surface. After the resist is lifted off, the second film with exposed portions of the whole top surface of the p-side ohmic electrode and the part of the n-side ohmic electrode is formed. The second insulating film may be formed so as to be spaced away from the p-side ohmic electrode. In addition, it may be formed so as to partially overlap the p-side ohmic electrode. Additionally, in consideration of a later dividing process, the first and second insulating films and the electrodes may not be formed in a strip-shaped region with a width of about 10 ?m that centers a dividing line.
The second insulating film is provided so as to lie on the whole surface except for the upper surface of the p-side and n-side ohmic electrodes. The film is preferably formed of a material of an oxide containing at least one element selected from the group consisting of Si, Ti, V, Zr, Nb, Hf and Ta, or at least one material selected from the group consisting SiN, BN, SiC, AlN and AlGaN. Single layer film or multilayer film of SiO 2 , Al 2 O 3 , ZrO 2 and TiO 2 can be given as a more preferable material among them.
(Pad Electrode)
Pad Electrodes are formed so as to cover the aforementioned ohmic electrodes. In this case, they are preferably formed so as to overlap the second insulating film. The p-side pad electrode has a lamination structure of Ni/Ti/Au (1000 ?/1000 ?/8000 ?) in this order. In addition, the n-side pad electrode is formed of Ni/Ti/Au (1000 ?/1000 ?/8000 ?) from the bottom side in this order. These pad electrodes are in contact with the p-side and n-side ohmic electrodes along stripe shapes so as to interpose the second insulating film between each pad electrode and each ohmic electrode.
(Cleavage and Resonance Surface Formation)
Subsequently, after the substrate is grinded to have a thickness of about 100 ?m, a scribe groove is formed on the substrate back surface. The wafer is cleaved into bar-shaped laser devices by breaking it from the nitride semiconductor side. The cleavage surface of the nitride semiconductor layer is the (1 1 00) M-plane of nitride semiconductor. This surface serves as a resonance surface.
(End Surface Protective Film Formation)
The resonance surface formed as described above is provided with an end surface protective film by means of a sputtering device such as ECR sputtering device. A third end surface protective film composed of two pairs of (SiO 2 (917 ?)/Nb 2 O 5 (550 ?)) is provided on an emission side end surface. A second end surface protective film composed of ZrO 2 (440 ?)+six pairs of (SiO 2 (667 ?)/ZrO 2 (440 ?)) is provided on a rear side end surface. In addition, a first end surface protective film composed of ZrO 2 (440 ?)+six pairs of (SiO 2 (917 ?)/ZrO 2 (605 ?)) is provided thereon. In the case where the wavelength of light emitted from the active layer is 400 nm, and the wavelength of luminescent radiation that is emitted by absorption of the wavelength of the light emitted from the active layer is 550 nm, as for the wavelengths (?), these thicknesses are set to ?/4n (where n is the refractive index). The transmittance of the end surface protective films that are set as described above is shown in graphs. FIG. 3 shows the transmittance on the emission side. FIG. 2 shows the transmittance on the rear side. In both the cases of the emission side and the rear side, the transmittance in the wavelength range of the luminescent radiation is low. Thus, the luminescent radiation is less prone to outgo.
Finally, a groove is formed so as to be in substantially parallel to the ridge stripe by scribing, and bars are cut at the groove, thus, a semiconductor laser device according to the present invention is obtained. The scribing can be performed by mechanical or physical scribing with a blade of a cutter, and so on, or by optical or thermal scribing with YAG laser. In addition, the scribing can be performed from the semiconductor layer side or the substrate side. Various methods can be suitably selected depending on the shapes of device, the types of substrate, and so on.
The nitride semiconductor laser device obtained as described above has a luminescent radiation region in almost the whole plane of the nitride semiconductor substrate. The reason is that it is grown such that the dislocation density difference is not large too much. Therefore, there is not a local region that has a high luminescent radiation intensity. The laser device can be driven into continuous wave with wavelength of 405 nm and high power of 60 mW, at a room temperature and a threshold current density of 2.5 kA/cm 2 . Since irradiation of the luminescent radiation on a detector provided on the rear side is suppressed, precise controlled driving can be provided. Additionally, the laser light emitted from the emission side end surface has less noise (unevenness), and has excellent FFP.
EJEMPLO 2
In an example 2, a third end surface protective film composed of Al 2 O 3 (1800 ?)/three pairs of (SiO 2 (917 ?)/Nb 2 O 5 (550 ?)) is provided on an emission side end surface. A second end surface protective film composed of ZrO 2 (440 ?)+six pairs of (SiO 2 (667 ?)/TiO 2 (370 ?)) is provided on a rear side end surface. In addition, a first end surface protective film composed of ZrO 2 (440 ?)+six pairs of (SiO 2 (917 ?)/TiO 2 (509 ?)) is provided thereon. Similarly to the example 1, in the case where the wavelength of light emitted from the active layer 104 is 400 nm, and the wavelength of luminescent radiation that is emitted by absorption of the wavelength of the light emitted from the active layer is 550 nm, as for the wavelengths (?), these thicknesses are set to ?/4n (where n is the refractive index). In addition, an n-electrode 107 is provided on the back surface of the nitride semiconductor substrate. V/Pt/Au (150 ?/2000 ?/3300 ?) is provided as the material of the n-electrode. After the n-electrode is provided, thermal treatment is not performed. Other processes except for the processes described above are performed similarly to the example 1, thus, a nitride semiconductor laser device according to the present invention is obtained. The nitride semiconductor laser device obtained as described above has a luminescent radiation region almost over the whole region of the substrate similarly to the example 1, and emits low luminescent radiation. Additionally, the laser device can be driven into continuous wave with wavelength of 405 nm and high power of 60 mW, at a room temperature and a threshold current density of 2.5 kA/cm 2 . Since irradiation of the luminescent radiation on a detector provided on the rear side, precise controlled driving can be provided. Additionally, the laser light emitted from the emission side end surface has less noise (unevenness), and has excellent FFP.
EJEMPLO 3
In an example 3, a substrate that is obtained as follows is used as a nitride semiconductor substrate. A GaAs substrate is used as a growth substrate. A stripe-shaped protective layer of SiO2 is formed in perpendicular to the M-plane of a nitride semiconductor on the upper surface of the substrate. A nitride semiconductor is grown by using this as a seed crystal such that the facet surface appears. Thus, a nitride semiconductor substrate 101 with thickness of 300 ?m is obtained. The nitride semiconductor substrate obtained as described above is a nitride semiconductor substrate has a stripe-shaped low dislocation density region and a dislocation flux region. A ridge is formed in the upper part of the low dislocation density region 112 . The low dislocation density 112 region is a luminescent radiation region. It absorbs light emitted from the active layer (405 nm) when a current is applied, and emits luminescent radiation (560 nm). In the example 3, although the n-electrode 107 is formed on the back surface of the nitride semiconductor substrate, before the ridge formation, etching is performed so as to expose the n-type semiconductor layer 102 . Particularly, the n-type semiconductor layer 102 to the p-type semiconductor layer 103 that are formed above the dislocation flux 111 with poor crystallinity has a growth condition different from its periphery. Accordingly, its thickness is small as compared with the periphery. It is considered that such a region does not have sufficient pn junction formation. For this reason, the n-type semiconductor layer to the p-type semiconductor layer in the region that has a width slightly wider than the strip-shaped dislocation flux is removed by etching, thus, it is possible to reduce deterioration of the device performance. Except for a process where a third end surface protective film composed of two pairs (Al2O3 (823 ?)/TiO2 (509 ?)) is provided on the emission-side end surface, processes are performed similarly to the example 1, thus, a nitride semiconductor laser device according to the present invention is obtained. In addition, in the example 3, similarly to the example 1, in the case where the wavelength of light emitted from the active layer is 400 nm, and the wavelength of luminescent radiation that is emitted by absorption of the wavelength of the light emitted from the active layer is 550 nm, as for the wavelengths (?), these thicknesses in the third end surface protective film are set to ?/4n (where n is the refractive index). The laser device obtained as described above can be driven into continuous wave with wavelength of 405 nm and high power of 60 mW, at a room temperature and a threshold current density of 2.5 kA/cm2. Since irradiation of the luminescent radiation on a detector provided on the rear side, precise controlled driving can be provided. Additionally, the laser light emitted from the emission side end surface has less noise (unevenness), and has excellent FFP.
The present invention can be applied to any devices to which laser devices can be applied such as CD player, MD player, various game machine devices, a DVD player, trunk line and the optical fiber communications systems for telephone line, submarine cable, etc., medical equipment including laser scalpel, laser therapy equipment and laser acupressure device, laser beam printer, printing device for display, etc., various measuring instruments, optical sensing device including laser level, laser measuring machine, laser speed gun laser thermometer, etc., and to various fields such as laser power carrying.
Marcos Pinto D`derlee
C.I. 17862728
Electronica del estado solido
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