JP2014236052A - Semiconductor laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element capable of obtaining sufficient reliability even in high-temperature and high-output drive.SOLUTION: A nitride semiconductor laser element 100 includes: a first coat film 114 which is formed in a light emission part and contains aluminum nitride crystal or aluminum oxynitride crystal; a second coat film 115 which is formed on the side opposite to the light emission part of the first coat film 114 and contains an oxide, oxynitride or nitride; and a DLC film 116 which is a radiation film formed on the side opposite to the first coat film 114 of the second coat film 115 and containing diamond-like carbon.

Description

  The present invention relates to a semiconductor laser device including a nitride semiconductor laser device.

  Conventionally, in a nitride semiconductor laser element among nitride semiconductor light emitting elements, a reliability failure due to deterioration of a light emitting portion is known. It is considered that the deterioration of the light emitting portion is caused by excessive heat generation of the light emitting portion due to the presence of the non-radiative recombination level. And as a main factor which a non-light-emission recombination level generate | occur | produces, the oxidation of a light emission part is considered.

Therefore, a coating film such as alumina (Al ₂ O ₃ ) or silicon oxide (SiO ₂ ) is formed on the light emitting part for the purpose of preventing oxidation of the light emitting part (see Patent Document 1).

JP 2002-335053 A

  We have been researching the realization of a nitride semiconductor laser device that does not cause poor reliability due to deterioration of the light emitting portion even during high output drive. When the following tests were conducted, further problems were found.

  A conventional nitridation is formed by forming a coat film made of alumina on the end face on the light emitting side to a thickness of 80 nm and forming a multilayer film of silicon oxide film / titanium oxide film on the end face on the light reflecting side to achieve a reflectivity of 95%. Aging test (30 ° C., CW drive, optical output 30 mW) under low temperature and low output conditions and aging test (70 ° C., CW drive, optical output 100 mW) under high temperature and high output conditions for semiconductor laser devices Two types of aging tests were performed. As a result, in the aging test under low temperature and low output conditions, the operation was stable even after exceeding 3000 hours. However, in the aging test under high temperature and high output conditions, the light emission was from around 400 hours. Many nitride semiconductor laser elements that stop the oscillation of the laser beam were observed due to the COD (Catastrophic Optical Damage). Therefore, it has been found that in the conventional nitride semiconductor laser device, the COD of the light emitting portion becomes a problem with a relatively short aging time of 400 hours under high temperature and high output conditions.

  An object of the present invention is to provide a semiconductor laser device capable of obtaining sufficient reliability even at high temperature and high output drive.

  To achieve the above object, a semiconductor laser device of the present invention includes a first coat film formed in a light emitting portion and including an aluminum nitride crystal or an aluminum oxynitride crystal, and the light emission of the first coat film. A second coat film containing oxide, oxynitride or nitride, and a heat dissipation film containing diamond-like carbon formed on the opposite side of the second coat film from the first coat film It is set as the structure provided with these.

  According to the present invention, it is possible to provide a semiconductor laser element capable of obtaining sufficient reliability even at high temperature and high output drive.

FIG. 3 is a schematic cross-sectional view of a preferred example of the nitride semiconductor laser element of the first embodiment. FIG. 2 is a schematic side view of the nitride semiconductor laser element shown in FIG. 1 in the cavity length direction. It is an electron beam diffraction pattern by TEM of the first coat film of the nitride semiconductor laser device of the first embodiment. 3 is an electron beam diffraction pattern by TEM of a region extending over two regions of the end surface of the nitride semiconductor laser device of the first embodiment and the first coat film. It is a figure which shows the relationship between the aging time of the nitride semiconductor laser element of this invention, and a COD level. It is a figure which shows the relationship between the aging time of the conventional nitride semiconductor laser element, and a COD level. It is a figure which shows the relationship between the aging time and COD level of the nitride semiconductor laser element in which the light emitting part formed the coat film containing the aluminum nitride crystal or the aluminum oxynitride crystal.

  Embodiments of the present invention will be described below. Although a nitride semiconductor laser element will be described below as an example, the present invention can also be applied to a semiconductor laser element having a laser structure made of AlGaInP, AlGaAs crystal or the like other than the nitride system. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

  In order to solve the above problem, the present inventor has performed aging under conditions of low temperature and low output (30 ° C., CW drive, light output 30 mW) and conditions of high temperature and high output (70 ° C., CW drive, light The change in the COD level of the conventional nitride semiconductor laser element having the above-described configuration after aging at an output of 100 mW was examined.

  FIG. 6 shows the relationship between the aging time and the COD level of a conventional nitride semiconductor laser device. In FIG. 6, the horizontal axis indicates the aging time, and the vertical axis indicates the COD level. Here, the COD level is obtained when the light output is increased by gradually increasing the drive current (CW drive) for each nitride semiconductor laser element after aging by changing the aging time under the above conditions. The light output value when the light emitting part CODs.

  As shown in FIG. 6, in the nitride semiconductor laser device after aging under low temperature and low output conditions, the aging time is about 100 hours, and the light emitting portion is deteriorated by COD. Even with increasing length, the COD level has hardly changed.

  On the other hand, even in a nitride semiconductor laser element after aging under high temperature and high output conditions, the aging time is about 100 hours, the COD of the light emitting portion is deteriorated, and the COD level is greatly reduced until the aging time is about 200 hours. do not do. However, when the aging time exceeds 400 hours, the COD level is greatly reduced.

  From the above results, the present inventor is the cause of the decrease in the reliability of the nitride semiconductor laser device due to the decrease in the COD level after aging time of 400 hours or more in aging under high temperature and high output conditions. I understood it.

  The cause of the decrease in the COD level after 400 hours is that the oxygen or O—H groups in the atmosphere pass through the coat film made of alumina formed on the end surface on the light output side to constitute the end surface on the light output side. It was thought that it reached the surface of the nitride semiconductor crystal and caused a decrease in the COD level because the nitride semiconductor crystal was oxidized. That is, it is considered that it took about 400 hours for oxygen or O—H groups in the atmosphere to pass through the 80 nm-thick coat film made of alumina.

  In most cases, the coating film formed on the end face on the light emitting side is formed using a method such as an EB (Electron Beam) vapor deposition method or a sputtering method. In this case, it is known that the coating film is almost amorphous. When TEM (Transmission Electron Microscopy) observation was performed on the end face of the nitride semiconductor laser element after the above test and the electron diffraction pattern of the coating film was observed, a halo pattern peculiar to amorphous was observed, and the coating film was It was confirmed to be amorphous.

  Since the amorphous coating film has a low density and contains many defects, it easily transmits oxygen or O—H groups in the atmosphere. Therefore, by forming a coating film containing aluminum nitride crystals or aluminum oxynitride crystals in the light emitting portion of the nitride semiconductor laser element, sufficient reliability was obtained at high temperature and high output drive.

  Further, when the crystal axis of the aluminum nitride crystal or the aluminum oxynitride crystal in the coat film is aligned with the crystal axis of the nitride semiconductor crystal constituting the light emitting portion, the high temperature and high output can be obtained. Reliability could be further improved in driving.

  Therefore, a laser in which the crystal axis of the aluminum oxynitride crystal in the coating film is aligned with the crystal axis of the nitride semiconductor crystal constituting the light emitting part is manufactured, and the laser output is 70 ° C., CW drive, and light output is 100 mW. The change in the COD level of the nitride semiconductor laser device having the above-described configuration after aging at 90 ° C., CW drive, and optical output of 300 mW was examined.

  FIG. 7 shows the relationship between the aging time and the COD level of a nitride semiconductor laser element in which a coating film containing an aluminum nitride crystal or an aluminum oxynitride crystal is formed in the light emitting portion. As shown in FIG. 7, at 70 ° C. and an optical output of 100 mW, the COD level does not decrease with time. However, it can be seen that at 90 ° C. and an optical output of 300 mW, the COD level gradually decreases with time.

  In this further aging of high temperature and high output (90 ° C., optical output 300 mW), the temperature of the element end face increased and the coat film on the end face deteriorated, so it is considered that the COD level gradually decreased with time.

  Therefore, in the present invention, an oxide, an oxynitride, or a nitride is further formed on the first coat film containing aluminum nitride crystal or aluminum oxynitride crystal (on the side opposite to the light emitting portion of the first coat film). A second coat film containing an object, and a diamond-like carbon (DLC) laminated film having excellent heat conduction on the second coat film (on the opposite side of the second coat film from the first coat film) Formed. This DLC film (heat dissipation film) reduces the temperature of the element end face, suppresses the reduction of the COD level, and can provide sufficient reliability in driving at high temperature and high output (90 ° C., optical output 300 mW).

  Specifically, a first coat film in which the crystal axis of the aluminum oxynitride crystal in the film is aligned with the crystal axis of the nitride semiconductor crystal constituting the light emitting part is formed on the end face of the light emitting part, A nitride semiconductor laser device in which a second coat film containing oxide, oxynitride or nitride was formed thereon and a DLC film was formed thereon was fabricated. Then, the device was aged at 90 ° C., CW drive, and optical output of 300 mW, and the change in the COD level of the nitride semiconductor laser device of the present invention having the above-described configuration after aging was examined.

  FIG. 5 shows the relationship between the aging time and the COD level of the nitride semiconductor laser device of the present invention. As shown in FIG. 5, even after aging for 1500 hours, the COD level was 640 mW, and it was confirmed that there was almost no deterioration from the initial COD level.

  Further, by laminating the DLC film excellent in heat conduction on the second coat film, it is possible to obtain a sufficient heat dissipation effect on the element end face. Further, by interposing the second coat film between the DLC film and the first coat film, mutual diffusion between the DLC film and the first coat film can be prevented, and a laser element free from a decrease in COD level can be obtained.

  On the other hand, when an oxide, oxynitride, or nitride film is formed on an amorphous aluminum nitride or aluminum oxynitride film that is not crystallized, and a DLC film is formed thereon, Interdiffusion of amorphous aluminum nitride or aluminum oxynitride film, oxide, oxynitride or nitride film, and DLC film occurred, and the reduction in COD level could not be suppressed .

  In the present invention, the thickness of the first coat film is preferably 6 nm or more and 150 nm or less. When the thickness of the first coat film is less than 6 nm, the thickness of the coat film may be too small to sufficiently suppress oxygen and the like from passing through the first coat film. Further, when the thickness of the first coat film exceeds 150 nm, the crystallized first coat film has a stronger internal stress than that of the amorphous case, and thus the first coat film is cracked. May cause problems.

  In the present invention, when the oxygen content of the first coat film containing the aluminum oxynitride crystal is more than 35 atomic% of the total atoms constituting the first coat film, the first coat film is made of alumina. Thus, the crystallinity of the aluminum oxynitride crystal is broken, and oxygen or the like tends not to be sufficiently prevented from passing through the first coat film. Therefore, in the present invention, the oxygen content in the first coat film containing the aluminum oxynitride crystal is preferably 35 atomic percent or less, and more preferably 15 atomic percent or less.

  In the nitride semiconductor laser device of the present invention, the active layer and the cladding layer formed on the substrate are at least one group 3 element and group 5 element selected from the group consisting of aluminum, indium and gallium. It means a device composed of a material containing 50% by mass or more of a compound with nitrogen.

<First Embodiment>
FIG. 1 shows a schematic cross-sectional view of a preferred example of the nitride semiconductor laser element of this embodiment. Here, the nitride semiconductor laser device 100 according to the present embodiment includes a buffer layer 102 made of n-type GaN and a thickness of 0.2 μm and an n-type Al _0.06 Ga _0.94 N on a semiconductor substrate 101 made of n-type GaN. N-type cladding layer 103 having a thickness of 2.3 μm, n-type guide layer 104 having a thickness of 0.02 μm made of n-type GaN, multiple quantum well active layer 105 made of InGaN having a thickness of 4 nm and GaN having a thickness of 8 nm, p P-type current blocking layer 106 made of p-type Al _0.3 Ga _0.7 N with a thickness of 20 nm, p-type cladding layer 107 made of p-type Al _0.05 Ga _0.95 N with a thickness of 0.5 μm, and p-type GaN with a thickness of 0.1 μm The p-type contact layer 108 is stacked by epitaxial growth in this order from the semiconductor substrate 101 side. In addition, the mixed crystal ratio of each said layer is adjusted suitably, and is not related to the essence of this invention. Further, the wavelength of the laser light oscillated from the nitride semiconductor laser element of the present embodiment can be appropriately adjusted in the range of 370 nm to 470 nm, for example, depending on the mixed crystal ratio of the multiple quantum well active layer 105. In the present embodiment, the wavelength of the laser beam is 405 nm.

  The nitride semiconductor laser device 100 is formed such that a part of the p-type cladding layer 107 and the p-type contact layer 108 is removed, and the striped ridge stripe portion 111 extends in the cavity length direction. . Here, the width of the stripe of the ridge stripe portion 111 is, for example, about 1.2 to 2.4 μm, and typically about 1.5 μm.

Further, a p-electrode 110 made of a laminate of a Pd layer, a Mo layer, and an Au layer is provided on the surface of the p-type contact layer 108, and a SiO ₂ layer is formed below the p-electrode 110 except for the formation of the ridge stripe portion 111. An insulating film 109 made of a laminate of a layer and a TiO ₂ layer is provided. In addition, an n-electrode 112 made of a laminate of an Hf layer and an Al layer is formed on the surface of the n-type GaN substrate 101 opposite to the layer on the layer side.

FIG. 2 is a schematic side view of the nitride semiconductor laser element 100 shown in FIG. 1 in the cavity length direction. Here, the light emitting side end face 113 of the nitride semiconductor laser element 100 contains aluminum oxynitride represented by a composition formula of Al _a O _b N _c (a + b + c = 1, 0 <b ≦ 0.35). The first coat film 114 is formed with a thickness of 6 nm. A second coat film 115 containing an aluminum oxide is formed on the first coat film 114 to a thickness of 80 nm. Further, the DLC film 116 is formed on the second coat film 115 with a thickness of 10 nm.

  In the above composition formula, Al represents aluminum, O represents oxygen, and N represents nitrogen. In the above composition formula, a represents the composition ratio of aluminum, b represents the composition ratio of oxygen, and c represents the composition ratio of nitrogen. When the coat film is formed by the sputtering method, argon or the like may be included to some extent, but here, it is expressed in terms of a composition ratio excluding argon other than Al, O, and N. That is, the sum of the composition ratios of Al, O, and N is set to 1.

  The end surface 117 on the light reflection side of the nitride semiconductor laser element 100 has an aluminum oxynitride film 118 having a thickness of 6 nm, an aluminum oxide film 119 having a thickness of 80 nm, and a silicon oxide film having a thickness of 71 nm. A high reflective film 120 in which a silicon oxide film with a thickness of 142 nm is laminated on the outermost surface after four pairs of titanium oxide films with a thickness of 46 nm are laminated as one pair (lamination starts from a silicon oxide film) is formed in this order. Yes.

  The first coat film 114, the second coat film 115, the DLC film 116, the aluminum oxynitride film 118, the aluminum oxide film 119, and the highly reflective film 120 are formed on the above semiconductor substrate, such as a buffer layer. After sequentially laminating the above nitride semiconductor layers and forming a ridge stripe portion, the wafer having the insulating film, p-electrode, and n-electrode formed thereon is cleaved to expose the end face 113 and the end face 117, which are cleavage faces, respectively. Are prepared on the end face 113 and the end face 117 of the sample, respectively.

  Before the first coat film 114 is formed, the end face 113 is heated at a temperature of, for example, 100 ° C. or more in the film forming apparatus to remove the oxide film or impurities attached to the end face 113 and clean it. However, it is not particularly necessary in the present invention. Further, the end face 113 may be cleaned by irradiating the end face 113 with, for example, argon or nitrogen plasma, but this is not particularly necessary in the present invention. It is also possible to irradiate plasma while heating the end face 113. As for the above-described plasma irradiation, for example, it is possible to irradiate nitrogen plasma after irradiating argon plasma, and the plasma may be irradiated in the reverse order. In addition to argon and nitrogen, for example, a rare gas such as helium, neon, xenon, or krypton can be used.

  The first coat film 114, the second coat film 115, and the DLC film 116 can be formed by, for example, an ECR (Electron Cyclotron Resonance) sputtering method, but other various sputtering methods or CVD (Chemical Vapor Deposition). ) Method or EB (Electron Beam) vapor deposition method.

  The contents (atomic%) of aluminum, nitrogen, and oxygen constituting the first coat film 114 can be measured by, for example, AES (Auger Electron Spectroscopy). The oxygen content constituting the first coat film 114 can also be measured by TEM-EDX (Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy).

  As a result of analyzing the composition of aluminum oxynitride separately produced in the thickness direction by AES under the same conditions as the end face coating film of the laser element, the content of aluminum constituting the oxynitride of aluminum is 34. It was found that the composition was almost uniform in the thickness direction with 8 atomic%, oxygen content of 3.8 atomic%, and nitrogen content of 61.4 atomic%. A very small amount of argon was also detected. Further, the argon content in the first coat film 114 is more than 0 atom% and less than 5 atom% when the total number of atoms of aluminum, oxygen, nitrogen and argon in the first coat film 114 is 100 atom%. However, the present invention is not limited to this.

  Further, the aluminum oxide film 115 on the light emitting side, the aluminum oxynitride film 118 on the light reflecting side, the aluminum oxide film 119 and the highly reflective film 120 are also the same as the first coat film 114 and the DLC film 116 described above. It can be formed by ECR sputtering or the like. Also, it is preferable to perform cleaning by heating and / or cleaning by plasma irradiation before forming these films. However, the deterioration of the light emitting portion is a problem on the light emitting side where the light density is large, and the light reflecting side has a light density lower than that on the light emitting side, so that deterioration is not a problem in many cases. Therefore, in the present invention, a film such as an aluminum oxynitride film may not be provided on the end surface 117 on the light reflection side. In the present embodiment, an aluminum oxynitride 118 having a thickness of 6 nm is formed on the end surface 117 on the light reflection side. The thickness of the aluminum oxynitride 118 is, for example, as thick as 50 nm. There is no problem.

  Further, after the above film is formed on the end face, heat treatment may be performed. As a result, it is possible to expect an improvement in film quality due to the removal of moisture contained in the film and the heat treatment.

  As described above, the first coat film 114, the second coat film 115, and the DLC film 116 are formed in this order on the end surface 113 on the light emitting side of the above sample, and aluminum oxynitride is formed on the end surface 117 on the light reflecting side. The nitride semiconductor laser device 100 of this embodiment is obtained by forming the material film 118, the aluminum oxide film 119, and the highly reflective film 120 in this order and then dividing them into chips.

  FIG. 3 shows an electron beam diffraction pattern of the first coat film 114 of the nitride semiconductor laser element 100 of the present embodiment by TEM, and FIG. 4 shows a region extending between the end surface 113 and the first coat film 114. The electron diffraction pattern by TEM is shown. In FIG. 4, the spot diameter is reduced in order to analyze two regions of the end face 113 and the first coat film 114.

  As shown in FIG. 3, since the electron beam diffraction pattern is dotted with diffraction spots, it can be seen that the oxynitride of aluminum constituting the first coat film 114 is crystallized.

  Also, the arrows shown in FIG. 4 indicate the diffraction spots of the first coat film 114, but as shown in FIG. 4, the diffraction spots of the first coat film 114 are nitride semiconductors that constitute the end face 113 on the light emission side. It almost coincides with the diffraction spot of the crystal. Therefore, it was confirmed that the crystal axes of the nitride semiconductor crystal constituting the light emitting side end face 113 and the aluminum oxynitride crystal constituting the first coat film 114 were aligned.

  Strictly speaking, FIG. 4 does not compare the diffraction spots of the light emitting portion of the nitride semiconductor laser device 100 and the first coat film 114, but the end surface 113 on the light emitting side is formed of a nitride semiconductor layer. Since it is the end face of the wafer formed by sequential epitaxial growth, it is considered that all the crystal axes of the nitride semiconductor crystal constituting the end face 113 on the light emission side are aligned. Therefore, the crystal axis of the nitride semiconductor crystal constituting the light emitting portion which is a part of the end surface 113 on the light emitting side of the nitride semiconductor laser device 100 and the crystal of the aluminum oxynitride crystal constituting the first coat film 114 It seems to be aligned with the axis.

  In FIG. 4, the diffraction spot of the first coat film 114 substantially coincides with the diffraction spot of the nitride semiconductor crystal forming the end face 113 on the light emitting side, but the nitriding forming the end face 113 on the light emitting side. Since the lattice constants of the oxide semiconductor crystal and the aluminum oxynitride crystal constituting the first coat film 114 are different, the positions of these diffraction spots may be somewhat shifted. In addition, in the central portion of FIG. 4, the diffraction spots of the nitride semiconductor crystal constituting the end surface 113 on the light emission side are large, and the diffraction spots of the first coat film 114 are hidden behind them.

  Table 1 shows the results of determining the interplanar spacing of the aluminum oxynitride crystals constituting the first coat film 114 from the diffraction spots of the first coat film 114 shown in FIG. The interplanar spacing of the aluminum nitride crystal shown on the JCPDS card as a reference is also shown. Here, the surface spacing in the C-axis direction of the first coat film 114 produced in the present embodiment was 2.48 angstroms (Å).

  Further, when the crystal system of the DLC film 116 was examined by TEM, a diffraction pattern in which a ring-shaped diffraction pattern overlapped with a halo pattern was confirmed, and it was found that the crystal was somewhat crystallized. When a TEM image was confirmed, no clear defects were confirmed.

  It was also confirmed that the TEM diffraction pattern of the DLC film separately produced on the sapphire substrate under the same conditions as the end face coating film of the laser element was amorphous with a halo pattern. When a TEM image of the DLC film on the sapphire substrate was confirmed, dark lines were observed, and it was found that there was a defect.

  Further, when the crystal system of the second coat film 115 was also examined by TEM, it was found that it was somewhat crystallized. When a TEM image was confirmed, no clear defects were confirmed.

  Next, the COD level of the nitride semiconductor laser device 100 before aging and after aging (90 ° C., CW drive, optical output 300 mW) was investigated. The result is shown in FIG. As shown in FIG. 5, the COD level before aging is about 700 mW, and it can be seen that even when the aging time exceeds 400 hours, the COD level hardly decreases.

  This is because, in the nitride semiconductor laser device 100, the aluminum oxynitride crystal constituting the first coat film 114 seems to have epitaxially grown on the nitride semiconductor crystal constituting the end surface 113 on the light emitting side. This is because the film has a very high crystallinity, and this high crystallinity effectively functions as a film that suppresses the permeation of oxygen compared to an amorphous coating film that is considered to contain many defects. Conceivable. This requires that the first coat film 114 does not deteriorate even at a high temperature of 90 ° C., and it is considered that the deterioration is suppressed by the heat dissipation effect of the DLC film 116.

Second Embodiment
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

  In the nitride semiconductor laser device of this embodiment, a first coat film 114 having a thickness of 20 nm containing aluminum nitride is formed on the end surface 113 on the light emitting side, and a silicon film having a thickness of 60 nm is formed on the first coat film 114. A second coat film 115 containing the nitride is formed, and a 200 nm thick DLC film 116 is formed on the second coat film 115.

  Further, an aluminum nitride film having a thickness of 12 nm is formed on the end face 117 on the light reflection side, and an aluminum oxide film having a thickness of 80 nm is formed on the aluminum nitride film, and the aluminum oxide film is formed. 4 pairs of a silicon oxide film having a thickness of 81 nm and a titanium oxide film having a thickness of 54 nm are stacked on top of each other (lamination starts from the silicon oxide film), and then a silicon oxide film having a thickness of 162 nm is stacked on the outermost surface. A reflective film is formed.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was investigated by the electron beam diffraction pattern of the TEM. As a result, the first coat film 114 was made of an aluminum nitride crystal. Was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the light exit side end face 113 and the aluminum nitride crystal constituting the first coat film 114 were aligned. The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

<Third Embodiment>
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

In the nitride semiconductor laser device of the present embodiment, the first coat film 114 having a thickness of 40 nm containing aluminum oxynitride represented by the composition formula of Al _0.33 O _0.11 N _0.56 is formed on the end surface 113 on the light emitting side. Then, a second coat film 115 containing aluminum oxide having a thickness of 240 nm is formed on the first coat film 114, and a DLC film 116 having a thickness of 20 nm is formed on the second coat film 115.

  Further, an aluminum nitride film having a thickness of 12 nm is formed on the end face 117 on the light reflection side, and an aluminum oxide film having a thickness of 80 nm is formed on the aluminum nitride film, and the aluminum oxide film is formed. 4 pairs of a silicon oxide film having a thickness of 81 nm and a titanium oxide film having a thickness of 54 nm are stacked on top of each other (lamination starts from the silicon oxide film), and then a silicon oxide film having a thickness of 162 nm is stacked on the outermost surface. A reflective film is formed.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was examined by the electron beam diffraction pattern of TEM. As a result, the first coat film 114 was composed of aluminum oxynitride crystals. It was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the end surface 113 on the light emission side and the aluminum oxynitride crystal constituting the first coat film 114 were aligned. . The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

<Fourth embodiment>
In the nitride semiconductor laser device of the present embodiment, the configuration of the film formed on the end surface 113 on the light emitting side and the configuration of the film formed on the end surface 117 on the light reflecting side are changed, and the wavelength of the oscillated laser light The structure is the same as that of the nitride semiconductor laser device of the second embodiment except that the thickness is 460 nm.

  In the nitride semiconductor laser device of this embodiment, a first coat film 114 having a thickness of 50 nm containing aluminum oxynitride is formed on the end surface 113 on the light emitting side, and a thickness of 60 nm is formed on the first coat film 114. A second coat film 115 containing silicon nitride is formed, and a DLC film 116 having a thickness of 50 nm is formed on the second coat film 115.

  Further, an aluminum oxynitride film having a thickness of 6 nm is formed on the end surface 117 on the light reflection side, and an aluminum oxide film having a thickness of 80 nm is formed on the aluminum oxynitride film. Four pairs of a silicon oxide film having a thickness of 81 nm and a titanium oxide film having a thickness of 54 nm are laminated on the material film as a pair, and then a silicon oxide film having a thickness of 162 nm is laminated on the outermost surface. A highly reflective film is formed.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was examined by the electron beam diffraction pattern of TEM. As a result, the first coat film 114 was composed of aluminum oxynitride crystals. It was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the end surface 113 on the light emission side and the aluminum oxynitride crystal constituting the first coat film 114 were aligned. . The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

<Fifth Embodiment>
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

In the nitride semiconductor laser device of this embodiment, a first coat film 114 having a thickness of 50 nm containing aluminum oxynitride represented by the composition formula of Al _0.30 O _0.25 N _0.45 is formed on the end surface 113 on the light emitting side. A second coat film 115 containing silicon nitride having a thickness of 110 nm is formed on the first coat film 114, and a DLC film 116 having a thickness of 70 nm is formed on the second coat film 115.

  Further, an aluminum oxynitride film having a thickness of 50 nm is formed on the end surface 117 on the light reflecting side, and a silicon oxide film having a thickness of 50 nm is formed on the aluminum oxynitride film, and the silicon oxide film is formed on the silicon oxide film. A highly reflective film in which a silicon oxide film having a thickness of 142 nm is laminated on the outermost surface after six pairs are laminated (lamination starts from a silicon oxide film) with a silicon oxide film having a thickness of 71 nm and a silicon nitride film having a thickness of 50 nm as one pair. Is formed.

  Since the silicon nitride film has higher moisture resistance and lower oxygen permeability than the silicon oxide film (that is, O—H groups and oxygen are less likely to diffuse than in the silicon oxide film), the aluminum constituting the first coat film 114 By forming the silicon nitride film constituting the second coat film on the oxynitride film, the tendency to suppress the oxidation of the end face 113 on the light emitting side due to the transmission of oxygen or the like increases.

  Here, the thickness of the silicon nitride film constituting the second coat film 115 is preferably 5 nm or more, and more preferably 80 nm or more. If the thickness of the silicon nitride film is less than 5 nm, it tends to be difficult to form a uniform film, and if it is 80 nm or more, the effect of suppressing the diffusion of oxygen tends to be higher. is there.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was examined by the electron beam diffraction pattern of TEM. As a result, the first coat film 114 was composed of aluminum oxynitride crystals. It was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the end surface 113 on the light emission side and the aluminum oxynitride crystal constituting the first coat film 114 were aligned. . The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

<Sixth Embodiment>
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

In the nitride semiconductor laser device of this embodiment, a first coat film 114 having a thickness of 30 nm containing aluminum oxynitride represented by the composition formula of Al _0.31 O _0.03 N _0.66 is formed on the end surface 113 on the light emitting side. A second coat film 115 containing silicon nitride having a thickness of 140 nm is formed on the first coat film 114, and a DLC film 116 having a thickness of 30 nm is formed on the second coat film 115. Here, the thickness of the silicon nitride film constituting the second coat film 115 is preferably 5 nm or more. This is because when the thickness of the silicon nitride film is less than 5 nm, it tends to be difficult to form a uniform film in a plane.

  Further, an aluminum oxynitride film having a thickness of 50 nm is formed on the end surface 117 on the light reflecting side, and a silicon oxide film having a thickness of 50 nm is formed on the aluminum oxynitride film, and the silicon oxide film is formed on the silicon oxide film. A highly reflective film in which a silicon oxide film having a thickness of 142 nm is laminated on the outermost surface after six pairs are laminated (lamination starts from a silicon oxide film) with a silicon oxide film having a thickness of 71 nm and a silicon nitride film having a thickness of 50 nm as one pair. Is formed.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was examined by the electron beam diffraction pattern of TEM. As a result, the first coat film 114 was composed of aluminum oxynitride crystals. It was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the end surface 113 on the light emission side and the aluminum oxynitride crystal constituting the first coat film 114 were aligned. . The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

<Seventh embodiment>
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

In the nitride semiconductor laser device of this embodiment, a first coat film 114 having a thickness of 30 nm containing aluminum oxynitride represented by the composition formula of Al _0.32 O _0.08 N _0.60 is formed on the end surface 113 on the light emitting side. ing. A 140 nm thick silicon nitride film and a 160 nm thick aluminum oxide film are formed on the first coat film 114, and the silicon nitride film and the aluminum oxide film are formed on the silicon nitride film. A second coat film 115 is formed. Further, a DLC film 116 is formed on the second coat film 115.

  Further, an aluminum oxynitride film having a thickness of 50 nm is formed on the end surface 117 on the light reflecting side, and a silicon oxide film having a thickness of 50 nm is formed on the aluminum oxynitride film, and the silicon oxide film is formed on the silicon oxide film. A highly reflective film in which a silicon oxide film having a thickness of 142 nm is laminated on the outermost surface after six pairs are laminated (lamination starts from a silicon oxide film) with a silicon oxide film having a thickness of 71 nm and a silicon nitride film having a thickness of 50 nm as one pair. Is formed.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was examined by the electron beam diffraction pattern of TEM. As a result, the first coat film 114 was composed of aluminum oxynitride crystals. It was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the end surface 113 on the light emission side and the aluminum oxynitride crystal constituting the first coat film 114 were aligned. . The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

  Also, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated in the same manner as described above by replacing the aluminum oxide film of the second coat film 115 with a silicon oxide film having a thickness of 140 nm. However, as described above, it was confirmed that there was almost no decrease even after aging for 1500 hours.

<Eighth Embodiment>
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

In the nitride semiconductor laser device of this embodiment, a first coat film 114 having a thickness of 60 nm containing aluminum oxynitride represented by the composition formula of Al _0.32 O _0.08 N _0.60 is formed on the end surface 113 on the light emitting side. A second coat film 115 containing silicon oxynitride having a thickness of 230 nm is formed on the first coat film 114, and a DLC film 116 having a thickness of 100 nm is formed on the second coat film 115.

Here, the silicon oxynitride film constituting the second coat film 115 is represented by a composition formula of Si _0.348 O _0.04 N _0.612 , the silicon content is 34.8 atomic%, and the oxygen content is 4. The content of 0 atomic% and nitrogen was 61.2 atomic%.

  Further, an aluminum oxynitride film having a thickness of 50 nm is formed on the end surface 117 on the light reflecting side, and a silicon oxide film having a thickness of 50 nm is formed on the aluminum oxynitride film, and the silicon oxide film is formed on the silicon oxide film. A highly reflective film in which a silicon oxide film having a thickness of 142 nm is laminated on the outermost surface after six pairs are laminated (lamination starts from a silicon oxide film) with a silicon oxide film having a thickness of 71 nm and a silicon nitride film having a thickness of 50 nm as one pair. Is formed.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was examined by the electron beam diffraction pattern of TEM. As a result, the first coat film 114 was composed of aluminum oxynitride crystals. It was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the end surface 113 on the light emission side and the aluminum oxynitride crystal constituting the first coat film 114 were aligned. . The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

<Ninth Embodiment>
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

In the nitride semiconductor laser device of this embodiment, the first coat film 114 having a thickness of 40 nm containing aluminum oxynitride represented by the composition formula of Al _0.32 O _0.08 N _0.60 is formed on the end surface 113 on the light emitting side. A second coat film 115 containing zirconium oxide having a thickness of 100 nm is formed on the first coat film 114, and a DLC film 116 having a thickness of 60 nm is formed on the second coat film 115.

  Further, an aluminum oxynitride film having a thickness of 50 nm is formed on the end surface 117 on the light reflecting side, and a silicon oxide film having a thickness of 50 nm is formed on the aluminum oxynitride film, and the silicon oxide film is formed on the silicon oxide film. A highly reflective film in which a silicon oxide film having a thickness of 142 nm is laminated on the outermost surface after six pairs are laminated (lamination starts from a silicon oxide film) with a silicon oxide film having a thickness of 71 nm and a silicon nitride film having a thickness of 50 nm as one pair. Is formed.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was examined by the electron beam diffraction pattern of TEM. As a result, the first coat film 114 was composed of aluminum oxynitride crystals. It was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the end surface 113 on the light emission side and the aluminum oxynitride crystal constituting the first coat film 114 were aligned. . The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

<Tenth Embodiment>
The nitride semiconductor laser device of this embodiment is the same as that of the first embodiment except that the configuration of the film formed on the end surface 113 on the light emission side and the configuration of the film formed on the end surface 117 on the light reflection side are changed. The structure is the same as that of the nitride semiconductor laser element.

  In the nitride semiconductor laser device of this embodiment, a first coat film 114 having a thickness of 50 nm containing aluminum nitride is formed on the end surface 113 on the light emission side, and a 140 nm thick nitride is formed on the first coat film 114. A second coat film 115 containing silicon is formed, and a DLC film 116 having a thickness of 50 nm is formed on the second coat film 115.

  Further, an aluminum nitride film having a thickness of 50 nm is formed on the end face 117 on the light reflecting side, a silicon oxide film having a thickness of 50 nm is formed on the aluminum nitride film, and the thickness is formed on the silicon oxide film. Six pairs of a 71 nm silicon oxide film and a 50 nm thick silicon nitride film are stacked (starting from the silicon oxide film), and then a highly reflective film in which a 142 nm thick silicon oxide film is stacked on the outermost surface is formed. Has been.

  Here, as in the first embodiment, the crystal system of the first coat film 114 was investigated by the electron beam diffraction pattern of the TEM. As a result, the first coat film 114 was made of an aluminum nitride crystal. Was confirmed. It was also confirmed by the electron beam diffraction pattern of the TEM that the crystal axes of the nitride semiconductor crystal constituting the light exit side end face 113 and the aluminum nitride crystal constituting the first coat film 114 were aligned. The DLC film 116 was also found to be free from defects by TEM observation.

  For the nitride semiconductor laser device of this embodiment, the COD level after aging (90 ° C., CW drive, optical output 300 mW) was investigated as in the first embodiment. As a result, it was confirmed that the COD level of the nitride semiconductor laser element of the present embodiment hardly decreased even after aging for 1500 hours.

In the first to tenth embodiments described above, an n-type GaN substrate is used as the semiconductor substrate 101. However, in one embodiment of the present invention, the nitride of the light emitting portion is added to the light emitting portion made of a nitride semiconductor crystal. One feature is to improve the reliability of the nitride semiconductor laser device by forming the first coat film 114 including an aluminum nitride crystal or an aluminum oxynitride crystal whose crystal axes are aligned with the semiconductor crystal. To do. Therefore, Al _S Ga _t N it is preferable to use a substrate made of a nitride semiconductor represented by (s + t = 1,0 ≦ s ≦ 1,0 ≦ t ≦ 1) of the formula in the semiconductor substrate 101, first coated From the viewpoint of reducing lattice mismatch with the film 114 and reducing defects and strain, it is preferable to use a nitride semiconductor substrate containing aluminum such as an AlN substrate or an AlGaN substrate as the semiconductor substrate 101.

  In the first to tenth embodiments, a nitride semiconductor laser element is manufactured by sequentially stacking nitride semiconductor layers on a semiconductor substrate 101 made of a nitride semiconductor. Depending on the growth surface of the layer, the surface state of the nitride semiconductor layer stacked on the growth surface of the semiconductor substrate 101 also changes, and the crystallinity of the first coat film 114 formed on the side surface of the nitride semiconductor layer also changes. Can do. Therefore, it has been found that the growth surface of the semiconductor substrate 101 of the nitride semiconductor laser element can affect the crystallinity of the first coat film 114. Here, the growth surface of the nitride semiconductor layer of the semiconductor substrate 101 made of a nitride semiconductor is a C plane {0001}, an A plane {11-20}, an R plane {1-102}, or an M plane {1-100}. Preferably, the off-angle of the growth surface is preferably within 2 ° from any one of these crystal faces.

  In addition, when expressing a crystal plane and a direction, it should be expressed by adding a bar on a required number, but since there are restrictions on expression means, in this specification, the required number is used. Instead of the expression with a bar on top, the symbol “-” is added in front of the required number.

  In each of the above embodiments, the second coat film 115 is formed on the first coat film 114 in order to control the reflectance. Examples of the second coat film 115 include an oxide film of aluminum, a silicon oxide film, a titanium oxide film, a hafnium oxide film, a zirconium oxide film, a niobium oxide film, a tantalum oxide film, an yttrium oxide film, and the like, aluminum Selected from the group consisting of a nitride film such as a nitride film or a silicon nitride film, and an oxynitride film such as an aluminum oxynitride film or a silicon oxynitride film having a composition different from that of the first coat film 114 At least one kind can be used.

  For example, as an example, an aluminum oxynitride film having a thickness of 20 nm and an oxygen content of 10 atomic% is used for the first coat film 114, and a first silicon film having a thickness of 63 nm is formed on the first coat film 114. A two-coat film 115 is formed, and a DLC film 116 having a thickness of 20 nm is formed on the second coat film 115. As described above, since the silicon nitride film has high moisture resistance and low oxygen permeability, it is considered that oxidation of the light emitting portion due to transmission of oxygen or the like can be suppressed.

  In the present invention, when the first coat film includes an aluminum oxynitride crystal, the oxygen content is graded (from the interface between the light emitting portion and the first coat film to the outermost surface of the first coat film). The oxygen content may gradually decrease or increase toward the surface). Actually, the oxygen content in the first coat film varies somewhat. Moreover, it is preferable that the oxygen content in the first coat film varies within a range of 35 atomic% or less.

  In the present invention, in order to achieve a desired reflectance, a multilayer structure having different refractive indexes may be provided on the inner side (light emitting part side) of the heat dissipation film (DCL film 116).

  Embodiments of the present invention are summarized below. A semiconductor laser device according to an embodiment of the present invention includes a first coat film 114 formed on a light emitting portion and including an aluminum nitride crystal or an aluminum oxynitride crystal, and the light emitting portion of the first coat film 114. A second coat film 115 containing oxide, oxynitride or nitride, and formed on the opposite side of the second coat film 115 from the first coat film 114 and containing diamond-like carbon. The heat dissipation film (DLC film 116) is provided.

  According to this configuration, the temperature of the element end face is reduced by the heat dissipation film excellent in heat conduction, the reduction of the COD level is suppressed, and sufficient reliability is achieved at high temperature and high output (90 ° C., optical output 300 mW). Can be obtained.

  In the semiconductor laser device, it is preferable that the aluminum nitride crystal or the aluminum oxynitride crystal has a crystal axis aligned with the semiconductor crystal constituting the light emitting portion.

  According to this configuration, the film quality of the DLC film 116 can be further improved, and a sufficient heat dissipation effect on the element end face can be obtained. As a result, reliability can be further improved in high temperature and high output driving.

  In the semiconductor laser element described above, the thickness of the first coat film 114 is preferably 6 nm or more and 150 nm or less.

  If the thickness of the first coat film 114 is less than 6 nm, the thickness of the first coat film 114 is too thin and oxygen or the like may not be sufficiently prevented from passing through the first coat film 114. is there. Further, when the thickness of the first coat film 114 exceeds 150 nm, the crystallized first coat film 114 has a stronger internal stress than that of the amorphous case, and therefore the first coat film 114. Problems such as cracks may occur.

  In the above semiconductor laser device, the second coat film may be, for example, an oxide film of aluminum, a silicon oxide film, a titanium oxide film, a hafnium oxide film, a zirconium oxide film, a niobium oxide film, a tantalum oxide film, It is an yttrium oxide film.

  In the semiconductor laser device described above, the second coat film is, for example, an oxynitride film of aluminum or a silicon oxynitride film having a composition different from that of the first coat film.

  In the above semiconductor laser device, the second coat film is, for example, an aluminum nitride film or a silicon nitride film as a nitride.

The semiconductor laser device of the above, it is preferable to use a substrate made of _{Al s Ga t N (s +} t = 1,0 ≦ s ≦ 1,0 ≦ t ≦ 1) nitride semiconductor represented by the composition formula.

  With this configuration, the first coat film 114 made of an aluminum nitride crystal or an aluminum oxynitride crystal whose crystal axes are aligned with the nitride semiconductor crystal of the light emitting portion is formed in the light emitting portion made of a semiconductor crystal. it can.

  In the present invention, the band gap is increased by averaging the composition of the active layer in the vicinity of the end face used in the GaAs semiconductor laser element, for example, in the end face portion including the light emitting portion, and the COD level is improved. It can also be used for a semiconductor laser device having a structure.

100 Nitride semiconductor laser device (semiconductor laser device)
101 Semiconductor substrate 114 First coat layer 115 Second coat film 116 DLC film (heat dissipation film)

Claims (5)

A first coat film formed on the light emitting portion and including an aluminum nitride crystal or an aluminum oxynitride crystal;
A second coat film formed on the opposite side of the first coating film from the light emitting portion and containing an oxide, oxynitride, or nitride;
A semiconductor laser device comprising: a heat dissipation film formed on the opposite side of the second coat film from the first coat film and containing diamond-like carbon.   2. The semiconductor laser device according to claim 1, wherein the aluminum nitride crystal or the aluminum oxynitride crystal has a crystal axis aligned with a semiconductor crystal constituting the light emitting portion.   3. The semiconductor laser device according to claim 1, wherein the thickness of the first coat film is 6 nm or more and 150 nm or less.   The second coat film includes an aluminum oxide film, a silicon oxide film, a titanium oxide film, a hafnium oxide film, a zirconium oxide film, a niobium oxide film, a tantalum oxide film, or an yttrium oxide film. 4. The semiconductor laser device according to any one of 3. _{Al s Ga t N (s +} t = 1,0 ≦ s ≦ 1,0 ≦ t ≦ 1) of claims 1 to 4, characterized in that by using a substrate made of a nitride semiconductor represented by the composition formula Any one of the semiconductor laser elements.