Nitride semiconductor laser element

Abstract

To provide a nitride semiconductor laser element in which the generation of end surface damages is reduced.SOLUTION: A nitride semiconductor laser element comprises: a first nitride semiconductor layer of a first conducive type; and a second nitride semiconductor layer of a second conductive type having a conductive type that is different from the first conductive type; an active layer that is arranged to between the first nitride semiconductor layer and the second nitride semiconductor layer; a light emission side end surface and a light reflection side end surface that are crossed to a side of the second nitride semiconductor layer of the active material layer; and a protection film that is provided onto the light emission side end surface. The protection film contains: a first Al containing film containing a first film that is formed by an oxide film containing aluminum and / or gallium, a second film formed by a nitride film, and aluminum and oxygen in order from the side of the light emission side end surface; and a second Al containing film containing a first silicon oxide film, aluminum, and oxygen; and a second silicon oxide film. The second silicon oxide film is arranged to the outermost side in the protection film.SELECTED DRAWING: Figure 1D

Description

[Technical field]

[0001] The present invention relates to a nitride semiconductor laser device. [Background technology]

[0002] 2. Description of the Related Art In recent years, various light emitting devices have been proposed that include a semiconductor laser or the like as an excitation light source and perform illumination or the like by utilizing excitation light emitted from this excitation light source. In such light emitting devices, a nitride-based semiconductor laser element has been proposed that prevents peeling of a protective film formed on the cavity facet (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-99959 A Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, in semiconductor lasers, where high output is required, facet damage (catastrophic optical damage) is one of the limiting factors in increasing output. In order to further increase output, it is necessary to reduce the occurrence of facet damage. [Means for solving the problem]

[0005] A nitride semiconductor laser element according to one embodiment of the present disclosure comprises a first nitride semiconductor layer of a first conductivity type, a second nitride semiconductor layer of a second conductivity type different from the first conductivity type, an active layer disposed between the first nitride semiconductor layer and the second nitride semiconductor layer, a light-emitting side end face and a light-reflecting side end face intersecting with a surface of the active layer on the second nitride semiconductor layer side, and a protective film provided on the light-emitting side end face, the protective film including, in order from the light-emitting side end face side, a first film made of an oxide film containing aluminum and / or gallium, a second film made of a nitride film, a first Al-containing film containing aluminum and oxygen, a first silicon oxide film, a second Al-containing film containing aluminum and oxygen, and a second silicon oxide film, the second silicon oxide film being disposed on the outermost side of the protective film. Effect of the Invention

[0006] According to the nitride semiconductor laser element of one embodiment of the present disclosure, it is possible to provide a nitride semiconductor laser element in which the occurrence of facet damage is reduced. [Brief description of the drawings]

[0007] [Figure 1A] 1 is a perspective view of a nitride semiconductor laser element according to one embodiment of the present invention; [Figure 1B] FIG. 1B is a front view of FIG. 1A. [Figure 1C] 1B is a cross-sectional view taken along line IC-IC in FIG. 1A. [Figure 1D] FIG. 4 is a partial enlarged view showing an example of a protective film on the light-emitting end face side. [Diagram 2] 1 is a high-resolution transmission electron microscope image of the protective film and its vicinity. [Figure 3A] 1 is an electron beam diffraction image of a first Al-containing film. [Figure 3B] Electron beam diffraction image of the second film. [Figure 3C] 1 is an electron beam diffraction image of the first film. [Figure 3D] 1 is an electron beam diffraction image of a nitride semiconductor laminate. [Figure 4]FIG. 2 is a cross-sectional view showing another example of the nitride semiconductor laser element of the present invention. [Diagram 5] FIG. 4 is a partial enlarged view showing an example of a protective film on the light reflecting end face side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the embodiment shown below is merely an example of a method for realizing the technical idea of ​​the present invention, and the present invention is not limited to the following embodiment. Furthermore, in the following description, the same names and symbols indicate the same or similar components, and detailed description will be omitted as appropriate.

[0009] A nitride semiconductor laser element (hereinafter sometimes referred to as a semiconductor laser element) according to this embodiment is shown in Figs. 1A to 1D. Fig. 1A is a perspective view of the nitride semiconductor laser element of this embodiment. Fig. 1B is a front view of Fig. 1A. Fig. 1C is a cross-sectional view taken along line IC-IC of Fig. 1A. Fig. 1D is a partial enlarged view showing an example of a protective film on the light-emitting end face side. Protective films 30 and 40 are omitted in Figs. 1A and 1B. The nitride semiconductor laser element 10 is an edge-emitting laser element. The nitride semiconductor laser element 10 includes a first nitride semiconductor layer 11, a second nitride semiconductor layer 12, an active layer 13 disposed between the first nitride semiconductor layer 11 and the second nitride semiconductor layer 12, and a protective film 30. The first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 have a light-emitting end face 14 and a light-reflecting end face 15 as faces intersecting with a face of the active layer 13 on the second nitride semiconductor layer 12 side. A stack including the first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 may be referred to as a nitride semiconductor stack. The protective film 30 is provided on the light-emitting end face 14. The protective film 30 includes, in order from the light-emitting end face 14 side, a first film 31 containing aluminum and / or gallium and oxygen, a second film 32 made of a nitride film, a first Al-containing film 33 containing aluminum and oxygen, a first silicon oxide film 34, a second Al-containing film 35 containing aluminum and oxygen, and a second silicon oxide film 36. The second silicon oxide film 36 is disposed on the outermost side of the protective film 30. By providing such a configuration, the occurrence of damage to the end face of the nitride semiconductor laser element 10 can be reduced. The reasons for obtaining this effect are considered to be as follows. First, since the first film 31 in the protective film 30 is a film containing oxygen, the resistance is unlikely to change during operation, and a decrease in resistance can be avoided. Furthermore, since the first Al-containing film 33 is a film containing oxygen, the possibility of the oxidation of the first Al-containing film 33 progressing can be reduced. Furthermore, since the second film 32, which is a nitride film, exists between the first film 31 and the first Al-containing film 33, the possibility of the second film 32 reacting with oxygen in the air or atmosphere to be oxidized and expanding can be reduced. Furthermore, since the first silicon oxide film 34, the second Al-containing film 35, and the second silicon oxide film 36 are included, the number of films constituting the protective film 30 increases compared to a case where they are not included. As a result, local peeling between films that may occur due to operation of the nitride semiconductor laser element 10 can be suppressed by the multiple films, and the possibility of local peeling occurring can be reduced. Since a silicon oxide film tends to react less with the sealing medium that seals the nitride semiconductor laser element 10 than an Al-containing film, by disposing the second silicon oxide film 36 on the outermost side, it is possible to reduce the possibility that the protective film 30 will react with the sealing medium (e.g., a gas containing oxygen) and be altered. As a result, it is believed that the occurrence of facet damage (COD) can be effectively reduced. By reducing the occurrence of facet damage, it is possible to extend the life of the nitride semiconductor laser element 10. Such an effect is particularly noticeable in a high-output nitride semiconductor laser element 10. The high-output nitride semiconductor laser element 10 has an optical density of, for example, 2 MW / cm 2The optical density of the nitride semiconductor laser element 10 is 200 MW / cm 2 or less. The high-output nitride semiconductor laser element 10 is, for example, an element having an output of 1 W or more when the transverse mode is multimode, and may be an element having an output of 5 W or more. The high-output nitride semiconductor laser element 10 is, for example, an element having an output of 0.1 W or more when the transverse mode is single mode. The output of the nitride semiconductor laser element 10 may be 3 W or less.

[0010] (First nitride semiconductor layer 11, active layer 13, second nitride semiconductor layer 12) A first nitride semiconductor layer 11, an active layer 13, and a second nitride semiconductor layer 12 are laminated in this order. A nitride semiconductor laminate including these semiconductor layers can be formed on a substrate 16. The nitride semiconductor laminate has crystallinity. The first nitride semiconductor layer 11 exhibits a first conductivity type, and the second nitride semiconductor layer 12 exhibits a second conductivity type. The first conductivity type may be either n-type or p-type. The second conductivity type means a conductivity type different from the first conductivity type. The first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 are made of In x Al y Ga 1-x-y N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). The first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may contain one or more of Si, Ge, etc. as an n-type impurity. The first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may contain one or more of Mg, Zn, etc. as a p-type impurity. The impurity may be, for example, 5×10 16 / cm 3 ~1×10 21 / cm 3 The first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may each include an undoped layer. An undoped layer refers to a layer that is not intentionally doped with impurities that exhibit n-type or p-type. An undoped layer is one in which the impurity concentration does not exceed the detection limit in the analysis results of secondary ion mass spectrometry (SIMS) or the like, or the impurity concentration is 1×10 16 / cm3 Each of the first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may have only one semiconductor layer, but preferably has two or more layers. The peak oscillation wavelength of a semiconductor laser formed by the first nitride semiconductor layer 11, the active layer 13 and the second nitride semiconductor layer 12 is, for example, not less than 200 nm and not more than 700 nm.

[0011] (First nitride semiconductor layer 11) The first nitride semiconductor layer 11 may have a multi-layer structure made of nitride semiconductors such as GaN, InGaN, AlGaN, etc. When the first nitride semiconductor layer 11 is formed on the substrate 16, the first nitride semiconductor layer 11 may have an underlayer, a cladding layer, a crack prevention layer, an intermediate layer, an optical guide layer, etc. Other semiconductor layers may also be included.

[0012] (Active layer 13) The active layer 13 has a quantum well structure. The active layer 13 may be either a multiple quantum well structure or a single quantum well structure. The active layer 13 may have a multi-layer structure made of nitride semiconductors such as GaN and InGaN. When the active layer 13 has a multiple quantum well structure, it may include, in order from the first nitride semiconductor layer 11 side, a well layer, an intermediate barrier layer, and a well layer. It may have multiple well layers and multiple intermediate barrier layers. The well layer is, for example, an InGaN layer. The intermediate barrier layer is, for example, an InGaN layer or a GaN layer. The active layer 13 is, for example, an undoped layer. The composition of the active layer 13 can be adjusted appropriately according to the oscillation wavelength of the nitride semiconductor laser device to be obtained. x Ga 1-x The well layer may be a layer made of N or the like. The In composition ratio x may be selected from the range of 0.01 to 0.50. This allows the oscillation peak wavelength of the semiconductor laser to be set in the range of 360 nm to 700 nm. The well layer may be a layer made of GaN or AlGaN.

[0013] (Second nitride semiconductor layer 12) The second nitride semiconductor layer 12 may have a multi-layer structure made of nitride semiconductors such as GaN, InGaN, AlGaN, etc. The second nitride semiconductor layer 12 may have a cladding layer, an optical guide layer, etc. It may also include other semiconductor layers. As long as an edge-emitting laser element is configured, the surface, i.e., the upper surface, of the second nitride semiconductor layer 12 may have a ridge 12a, or a current confinement layer known in the art may be disposed in the second nitride semiconductor layer 12. For example, the second nitride semiconductor layer 12 is a p-type semiconductor layer, and the ridge 12a is formed on the upper surface thereof. The second nitride semiconductor layer 12 may also be an n-type semiconductor layer. The ridge 12a functions as an optical waveguide region, and its width may be 1 μm or more and 30 μm or less. When the nitride semiconductor laser element 10 is driven at high output, the width of the ridge 12a may be 1.5 μm or more and 500 μm or less. The height of the ridge 12a may be 0.1 μm or more and 2 μm or less. The degree of optical confinement can be appropriately adjusted by adjusting the thickness, material, etc. of the layers constituting the second nitride semiconductor layer 12. The length of the ridge 12a in the cavity direction may be 200 μm or more and 5000 μm or less. The width of the ridge 12a does not have to be the same in the cavity direction, and the side surface may be vertical or tapered. In this case, the taper angle may be 45 degrees or more and less than 90 degrees.

[0014] The crystal plane of the stacking surface of each of the first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 is not particularly limited, and may be any of the C-plane {0001}, the M-plane {1-100}, the A-plane {11-20}, and the R-plane {1-102}, or may be a plane other than these. For example, the upper surface of the second nitride semiconductor layer 12 is the C-plane. When expressing crystal planes and directions, the opposite direction of 1 is represented by a bar above 1 according to the notation of crystallography, but is represented by "-1" for convenience. Also, an individual orientation is represented by [], a collective orientation by <>, an individual plane by (), and a collective plane by {}.

[0015] (Light emitting end surface 14 and light reflecting end surface 15) The light emitting end face 14 and the light reflecting end face 15 are end faces of the semiconductor layer including at least the light emitting face 14a and the light reflecting face on both sides of the region corresponding to the optical waveguide region or NFP (near field pattern) of the active layer 13. The light emitting end face 14 and the light reflecting end face 15 are faces intersecting with the stacking plane (XY plane in FIG. 1A) of the first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12. The light emitting end face 14 and the light reflecting end face 15 may be inclined with respect to the stacking direction of the semiconductor layer (the direction of the arrow Z in FIG. 1A), but are preferably parallel. In addition, they are preferably perpendicular to the stacking plane of the semiconductor layer (XY plane in FIG. 1A). The light emitting end face 14 and the light reflecting end face 15 are faces facing each other and are preferably arranged parallel to each other. A resonator is formed between the light emitting end face 14 and the light reflecting end face 15. Here, "parallel" includes a difference within ±5 degrees. Here, "perpendicular" includes a difference within ±5 degrees. The light emitting end face 14 and the light reflecting end face 15 may be any of M-plane {1-100}, A-plane {11-20}, C-plane {0001}, and R-plane {1-102}, or may be other planes. For example, the light emitting end face 14 is an M-plane. When the light emitting end face 14 and the light reflecting end face 15 are M-planes, these planes may be obtained by cleavage. The cleavage can be performed, for example, by forming a recess by laser processing and then pressing. The scanning direction of the laser processing and the proceeding direction of the cleavage may be the same or different. The light emitting end face 14 does not have to be a strict M-plane.

[0016] (Protective film 30) The protective film 30 (first protective film) includes, on the light emitting end face 14, a first film 31 containing aluminum and / or gallium and oxygen, a second film 32 made of a nitride film, a first Al-containing film 33 containing aluminum and oxygen, a first silicon oxide film 34, a second Al-containing film 35 containing aluminum and oxygen, and a second silicon oxide film 36, in this order from the light emitting end face 14 side. The protective film 30 may include films other than these. The protective film 30 is, for example, composed of only these films. The protective film 30 provided on the light-emitting end face 14 covers the cavity facet formed in the semiconductor layer, but does not necessarily have to cover the entire surface of the light-emitting end face 14. The protective film 30 covers at least the region corresponding to the optical waveguide region or NFP of the cavity facet, that is, the light-emitting facet 14a which is the end face of the region covering the active layer 13 and a part of the layers above and below it. The protective film 30 may cover the entire surface of the light-emitting end face 14. A part of the protective film 30 may be disposed on a surface other than the cavity facet, for example, on the upper surface or side surface of the semiconductor layer. Each film constituting the protective film 30 is formed of a material transparent to the oscillation wavelength of the nitride semiconductor laser element 10.

[0017] (1st film 31) The first film 31 is a film disposed in contact with the light-emitting end face 14. "In contact" does not only mean that the first film 31 is in direct contact with the cavity facet, but also that the first film 31 may be formed on a thin film formed on the cavity facet to such an extent that the effect of the present invention is achieved. For example, a thin film formed by pre-treatment of the cavity facet, the atmosphere at the start of film formation, or the like may be present. The thickness of such a thin film is, for example, less than the thickness of the first film 31. The thickness of such a thin film may be, for example, 3 nm or less, or 1 nm or less. Such a thin film contains, for example, gallium (Ga) and oxygen (O). The first film 31 may be any of an oxide film containing aluminum (Al), an oxide film containing Ga, and an oxide film containing Al and Ga. An example of an oxide film containing Al is a film made of aluminum oxide, for example, a film made of Al2O3. An example of an oxide film containing Ga is a film made of gallium oxide, for example, a film made of Ga2O3. An example of an oxide film containing Al and Ga is a film made of aluminum gallium oxide, for example, a film made of AlGaO. By using such a film, it is possible to suppress a change in resistance during operation of the semiconductor laser element. In addition, since the first film 31 is an oxide film containing Al, a film having crystallinity can be easily formed. The first film 31 is, for example, a film made of Al2O3. The first film 31 may be an insulating film. The first film 31 is preferably a crystalline film. When the first film 31 is a crystalline film, the second film 32 can be easily formed as a crystalline film, and an oxidation reaction between the first film 31 and the light-emitting end face 14 is unlikely to occur. When the first film 31 has crystallinity, the first film 31 is a single crystal, a polycrystal, or a film that is a mixture of both. In a single crystal, there is almost no variation in the lattice constant in the material, and there is almost no lattice plane inclination. In other words, the atomic arrangement in the material is regularly arranged, and long-range order is maintained. A polycrystal is composed of many small single crystals, that is, microcrystals. The crystallinity of such a film can be determined by a diffraction image by an electron beam. By irradiating an electron beam on the film, an electron beam diffraction image appears corresponding to the size of the lattice constant and the surface direction. For example, in the case of a single crystal, diffraction points are observed to be regularly arranged. In the case of a polycrystal, since it is composed of microcrystals, the orientation of each lattice plane is not aligned, and the diffraction points are seen to be in a complex state of alignment, or Debye rings are seen. On the other hand, in the case of amorphous, the atomic arrangement does not have a long-distance periodic structure, so electron beam diffraction does not occur. Therefore, the diffraction image is observed without diffraction points. The electron beam diffraction image can be observed by cutting the film so that the cross section is exposed at the end face on which the film is formed, and applying an electron beam. The difference in crystallinity can be confirmed, for example, by cross-sectional observation using a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), a scanning electron microscope (SEM), etc., or by the difference in etching rate using an appropriate etchant such as an acid or alkaline solution. The atomic arrangement may be confirmed by an image obtained by high-resolution transmission electron microscopy (HRTEM).

[0018] FIG. 2 shows an example of a high-resolution transmission electron microscope image of the protective film 30 and its vicinity. The line at the bottom right of FIG. 2 indicates 5 nm. The nitride semiconductor laminate shown in FIG. 2 includes an active layer 13. FIG. 3A is an electron beam diffraction image at the circle indicated by A in FIG. 2, which is an electron beam diffraction image of the first Al-containing film 33. FIG. 3B is an electron beam diffraction image at the circle indicated by B in FIG. 2, which is an electron beam diffraction image of the second film 32. FIG. 3C is an electron beam diffraction image at the circle indicated by C in FIG. 2, which is an electron beam diffraction image of the first film 31. FIG. 3D is an electron beam diffraction image at the circle indicated by D in FIG. 2, which is an electron beam diffraction image of the nitride semiconductor laminate. From FIG. 3C, it was confirmed that the first film 31 was crystalline, that is, the first film 31 was a film having crystallinity. From FIG. 3D, it was confirmed that the nitride semiconductor laminate was crystalline, that is, the nitride semiconductor laminate had crystallinity.

[0019] Examples of the crystal structure of the first film 31 include cubic, tetragonal, and hexagonal crystals. The material, crystallinity, orientation, and the like of the first film 31 can be selected according to the material, crystallinity, orientation, and the like of the light-emitting end face 14 on which the first film 31 is formed. Examples of a film having crystallinity include a film partially containing single crystals and / or polycrystals, or a film composed only of single crystals and / or polycrystals. In other words, the first film 31 does not necessarily have to be strictly single crystal or polycrystal, and may have a crystal structure close to these or a crystal structure that exhibits the characteristics of these crystal structures. The crystallinity of the first film 31 may be different between a region corresponding to the optical waveguide region or NFP and the side of the active layer 13, the side of the first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 farther from the active layer 13 in the thickness direction. It is preferable that the first film 31 is crystalline over substantially the entire area in the thickness direction in the region corresponding to the optical waveguide region or NFP. Substantially the entire area in the thickness direction refers to the entire remaining area excluding areas where the boundaries between adjacent films are difficult to distinguish. For example, the first film 31 is a film that contains polycrystals at least in a part thereof. The first film 31 may be a film in which more than half of the area adjacent to the active layer 13 is composed of polycrystals when observing a cross section cut in a direction intersecting the main surface of the active layer 13 and intersecting the light-emitting end face 14 (for example, in a direction perpendicular to each other). The thickness of the first film 31 may be 1 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less, and more preferably 1 nm or more and 10 nm or less. The smaller the thickness of the first film 31, the easier it is to form a film with good crystallinity. The thickness of the first film 31 may be 5 nm or more, 6 nm or more, or may be 8 nm or more. When the thickness of the first film 31 is 5 nm or more, the life of the nitride semiconductor laser element 10 can be further extended. This is considered to be because the crystallinity of the second film 32 is improved. The thickness of the first film 31 may be 50 nm or less, 20 nm or less, 10 nm or less, or less than 10 nm. For example, the thickness of the first film 31 may be 5 nm or more and 10 nm or less. The thickness of the first film 31 may be less than 10 nm, or may be 5 nm or more and less than 10 nm. The thickness of the first film 31 refers to the length in a direction parallel to the main surface of the active layer 13. Similarly, the thickness of the second film 32 and the thickness of the first Al-containing film 33 refer to the length in the direction parallel to the principal surface of the active layer 13 .

[0020] The first film 31 can be formed by a method known in the art. For example, pulse sputtering, electron cyclotron resonance (ECR) sputtering, magnetron sputtering, ion beam assisted deposition, laser ablation, chemical vapor deposition (CVD), or a combination of two or more of these methods can be used. Alternatively, these methods may be combined with a full or partial pretreatment. As the pretreatment, for example, one or more of the following can be used: irradiation with an inert gas (Ar, He, Xe, etc.) or plasma, irradiation with oxygen or ozone gas, oxidation treatment (heat treatment), and exposure treatment. The first film 31 is preferably formed by pulse sputtering or ECR sputtering. For example, the first film 31 can be formed by using an ECR sputtering device. This allows the first film 31 to be obtained as a film with good crystallinity. When the first film 31 is formed by using an ECR sputtering device, the oxygen flow rate during formation is 1.33×10 -7 m 3 / s or more is preferable. A pretreatment may be performed before forming the first film 31. An example of the pretreatment is treating the light-emitting end surface 14 with oxygen plasma. Examples of the pulse sputtering method include a method using an oxide target, and a method using a non-oxide target and intermittently sputtering while irradiating oxygen gas or plasma or the like or in an oxygen atmosphere. The ECR sputtering method tends to be able to lower the temperature during film formation than the pulse sputtering method. This makes it possible to suppress the deterioration of the characteristics of the electrode, which will be described later.

[0021] In this way, by forming the first film 31 as a film containing oxygen in contact with the light-emitting end face 14, it is possible to suppress a change in resistance when the nitride semiconductor laser element 10 is driven. Furthermore, by forming the first film 31 as a crystalline film, it is easy to form the second film 32 as a crystalline film. Furthermore, since the first film 31 has a relatively small thickness, for example, thinner than the first Al-containing film 33, it is considered possible to alleviate stress caused by heat generated by driving at the light-emitting end face 14 when the nitride semiconductor laser element 10 is driven. Furthermore, it is possible to improve the adhesion between the light-emitting end face 14 and the protective film 30.

[0022] (2nd membrane 32) The second film 32 is a film disposed in contact with the first film 31. The second film 32 is a nitride film. Specific examples of nitride films include films made of AlN, GaN, AlGaN, and the like. Among them, an AlN film is preferable. Since an AlN film can be formed by an ECR sputtering method, for example, both the first film 31 and the second film 32 can be formed using an ECR sputtering device. The first film 31 and the second film 32 can be grown continuously. The second film 32 is preferably a film having crystallinity. This allows it to effectively act as an oxygen barrier film. This reduces the possibility that the light-emitting end face 14 will be oxidized by oxygen from outside the first Al-containing film 33 or the nitride semiconductor laser element 10. The orientation of the second film 32 in the thickness direction is along the M axis <1-100>, A axis <11-20>, C axis <11-20>, and <0001> and R-axis <1-102> orientation, or other orientations are also acceptable. For example, the second film 32 is C-axis oriented with respect to the M-axis of the nitride semiconductor laminate. In this case, the M-axis of the nitride semiconductor laminate and the C-axis of the second film 32 are parallel. The axial orientation of the crystal in the region of the second film 32 adjacent to the active layer 13 may be the same as the axial orientation of the crystal in the region of the second film 32 adjacent to the first nitride semiconductor layer 11 and / or the region of the second film 32 adjacent to the second nitride semiconductor layer 12. This makes it easy to form the second film 32 with good crystallinity. For example, in the second film 32, the region adjacent to the active layer 13 and the region adjacent to the first nitride semiconductor layer 11 and / or the second nitride semiconductor layer 12 are both C-axis oriented. For example, the C-axis of the region of the second film 32 adjacent to the active layer 13 is parallel to the C-axis of the region of the second film 32 adjacent to the first nitride semiconductor layer 11 and / or the second nitride semiconductor layer 12. The region of the second film 32 adjacent to a specific layer (e.g., the active layer 13) refers to a region of the second film 32 sandwiched between an extension plane (virtual plane) of one main surface of the layer and an extension plane (virtual plane) of the other main surface of the layer. The second film 32 may have the same axial orientation of the crystals throughout. The crystallinity of each region of the second film 32 can be evaluated using a cross section cut in a direction intersecting (e.g., perpendicular) to the main surface of the active layer 13. The thickness of the second film 32 may be 5 nm or more and 500 nm or less, and may be 5 nm or more and 200 nm or less, 5 nm or more and 100 nm or less, or 5 nm or more and 50 nm or less. By making the second film 32 have a thickness in such a range, a film with good crystallinity can be obtained, and the film can effectively function as an oxygen barrier film. It is considered that the thickness of the second film 32 being 50 nm or less makes it easier to suppress the occurrence of cracks. In order to adjust the reflectance of the protective film 30, the thickness of the second film 32 may be greater than 50 nm. The thickness of the second film 32 may be 20 nm or more, or 40 nm or more. This can further extend the life. The thickness of the second film 32 may be 20 nm or more and 100 nm or less, 40 nm or more and 100 nm or less, or 40 nm or more and 50 nm or less. This can further extend the life of the nitride semiconductor laser element 10. The second film 32 can be formed by a known method such as a sputtering method, an ECR sputtering method, etc. Examples of the sputtering method include a method using a nitride target, a method using a non-nitride target and sputtering while irradiating nitrogen gas or plasma or the like or in a nitrogen atmosphere. Regarding the example of the second film 32 shown in FIG. 2, it was confirmed from FIG. 3B that the second film 32 was crystalline, that is, the second film 32 was a film having crystallinity.

[0023] (1st Al-containing film 33) The first Al-containing film 33 can be disposed in contact with the second film 32. The first Al-containing film 33 is a film containing Al and O. The first Al-containing film 33 may be an oxide film containing Al or an oxynitride film containing Al. The first Al-containing film 33 may be a film made of aluminum oxide. By using such a film, the possibility of the first Al-containing film 33 being oxidized can be reduced, and therefore the possibility of oxygen reaching the nitride semiconductor stack can be reduced. It is considered that the oxidation of the first Al-containing film 33 during operation of the nitride semiconductor laser element 10 is less likely to progress in an oxide film containing Al than in an oxynitride film containing Al. As a result, it is possible to further extend the life of the nitride semiconductor laser element 10. The first Al-containing film 33 is, for example, a film made of Al2O3.

[0024] The first Al-containing film 33 may be a film having crystallinity or may be a film including an amorphous structure. The amorphous structure means a structure that does not have a periodic structure like the atomic arrangement in a crystal, that is, a structure in which the atomic arrangement is irregular and has no long-range order. The first Al-containing film 33 is preferably a film having an amorphous structure or a film including an amorphous structure and a crystalline structure, and is preferably a film consisting of only an amorphous structure. This makes it easier to make the thickness of the first Al-containing film 33 larger than the thickness of the first film 31 and / or the second film 32. When the first Al-containing film 33 includes an amorphous structure, a part of the first Al-containing film 33, for example, a part on the active layer 13 side, may become a film having crystallinity by driving the nitride semiconductor laser element 10. This is considered to further extend the life of the nitride semiconductor laser element 10. For example, when the first Al-containing film 33 is a film made of Al2O3, such crystallization may occur.

[0025] The thickness of the first Al-containing film 33 is preferably larger than that of the first film 31. The thickness of the first Al-containing film 33 may be smaller than that of the second film 32, but is preferably larger. This can increase the total thickness of the protective film 30. The thickness of the first Al-containing film 33 is, for example, three times or more the thickness of the first film 31, and may be ten times or more. The thickness of the first Al-containing film 33 is preferably 10 nm or more and 1000 nm or less, and more preferably 50 nm or more and 500 nm or less. By making the first Al-containing film 33 have a thickness in such a range, the total thickness of the protective film 30 can be increased, and therefore it is possible to reduce the possibility that oxygen from outside the nitride semiconductor laser element 10 passes through the protective film 30 and reaches the nitride semiconductor stack. This is considered to be advantageous in extending the life. In particular, when the first film 31 and the second film 32 are formed as films thinner than the first Al-containing film 33 in order to fulfill their functions, a more significant effect can be obtained. In addition, when the first Al-containing film 33 includes an amorphous structure, crystallization due to driving is unlikely to occur if the film is too thin. From this viewpoint, the thickness of the first Al-containing film 33 is preferably in the above-mentioned range. From this viewpoint, the thickness of the first Al-containing film 33 is preferably greater than the thickness of the second Al-containing film 35. The thickness of the first Al-containing film 33 may be within ±25% of (λ / 2n3)×2. λ is the oscillation wavelength of the nitride semiconductor laser element 10, and n3 is the refractive index of the first Al-containing film 33 at the oscillation wavelength λ. This allows the nitride semiconductor laser element 10 to have a longer life than when the thickness of the first Al-containing film 33 is made smaller. This is considered to be because the time it takes for the destruction proceeding from inside the nitride semiconductor laser element 10 to reach the outer surface of the protective film 30 can be extended by increasing the thickness of the protective film 30. As shown in FIG. 4, a part of the protective film 30 may be provided on the upper surface side and / or the lower surface side of the nitride semiconductor laminate. FIG. 4 is a cross-sectional view showing another example of the nitride semiconductor laser device 10. As shown in FIG.It is believed that providing protective film 30 in this manner can lengthen the distance until destruction reaches the outer surface of nitride semiconductor laser element 10 on the upper and / or lower sides of the nitride semiconductor laminate by the thickness of protective film 30. As a result, the life of nitride semiconductor laser element 10 can be extended.

[0026] The first Al-containing film 33 can be formed by a known method such as a sputtering method or an ECR sputtering method. For example, it can be formed using an ECR sputtering device. When the first film 31 and the first Al-containing film 33 are formed using an ECR sputtering device, the oxygen flow rate during the formation of the first Al-containing film 33 is lower than the oxygen flow rate during the formation of the first film 31. This allows the first film 31 to be formed as a crystalline film, and the first Al-containing film 33 to be formed as a film with an amorphous structure. Regarding the example of the first Al-containing film 33 shown in FIG. 2, it was confirmed from FIG. 3A that the first Al-containing film 33 was amorphous, that is, the first Al-containing film 33 was a film with an amorphous structure.

[0027] (First silicon oxide film 34) The first silicon oxide film 34 is provided on the side of the first Al-containing film 33 opposite to the second film 32. The first silicon oxide film 34 can be disposed in contact with the first Al-containing film 33. By providing the first silicon oxide film 34, the distance that destruction proceeding from inside the nitride semiconductor laser element 10 travels until it reaches the outer surface of the protective film 30 can be made longer compared to the case where the first silicon oxide film 34 is not provided. For example, the refractive index n4 at the oscillation wavelength λ of the first silicon oxide film 34 is smaller than the refractive index n3 at the oscillation wavelength λ of the first Al-containing film 33. The first silicon oxide film 34 may be, for example, a film made of silicon oxide (e.g., SiO2). This has the advantage of being able to suppress deterioration of initial characteristics and heat generation due to light absorption. The thickness of the first silicon oxide film 34 may be smaller than the thickness of the first Al-containing film 33. For example, the thickness of the first silicon oxide film 34 can be set within the range of ±5% of λ / 4n4. The first silicon oxide film 34 is preferably a film including an amorphous structure. This can improve the adhesion with the first Al-containing film 33. In addition, when the first Al-containing film 33 is a film including an amorphous structure and is crystallized by driving, it is considered that the first silicon oxide film 34 can adjust the excess or shortage of oxygen. That is, it is considered that it is possible to release the excess oxygen for the crystallization of the first Al-containing film 33 to the first silicon oxide film 34, and also possible to supply the shortage of oxygen for the crystallization of the first Al-containing film 33 from the first silicon oxide film 34. The first silicon oxide film 34 can be formed by a known method such as a sputtering method or an ECR sputtering method.

[0028] (Second Al-containing film 35) The second Al-containing film 35 is provided on the side of the first silicon oxide film 34 opposite to the first Al-containing film 33. The second Al-containing film 35 can be disposed in contact with the first silicon oxide film 34. By providing the second Al-containing film 35, the distance that destruction proceeding from inside the nitride semiconductor laser element 10 travels until it reaches the outer surface of the protective film 30 can be made longer compared to the case where the second Al-containing film 35 is not provided. The second Al-containing film 35 may be made of the same material as the first Al-containing film 33. The second Al-containing film 35 is a film made of, for example, Al2O3. The second Al-containing film 35 is preferably a film including an amorphous structure. This can improve adhesion to the first silicon oxide film 34. When the first Al-containing film 33 is crystallized by driving the nitride semiconductor laser element 10, the second Al-containing film 35 does not need to be crystallized by driving the nitride semiconductor laser element 10. The reflectance of the protective film 30 can be adjusted by the thickness of the second Al-containing film 35. For example, the thickness of the second Al-containing film 35 is smaller than the thickness of the first Al-containing film 33. The thickness of the second Al-containing film 35 can be set within a range of ±5% of λ / 4n5, where n5 is the refractive index of the second Al-containing film 35 at the oscillation wavelength λ. The second Al-containing film 35 can be formed by a known method such as a sputtering method, an ECR sputtering method, etc. For example, it can be formed by using an ECR sputtering device.

[0029] (Second silicon oxide film 36) The second silicon oxide film 36 is provided on the opposite side of the second Al-containing film 35 to the first silicon oxide film 34. The second silicon oxide film 36 can be arranged in contact with the second Al-containing film 35. By providing the second silicon oxide film 36, the distance that destruction proceeding from inside the nitride semiconductor laser element 10 travels until it reaches the outer surface of the protective film 30 can be increased compared to when the second silicon oxide film 36 is not provided. One of the causes of sudden death of the nitride semiconductor laser element 10 is the protective film 30 being blown away, but by providing the second silicon oxide film 36, the overall thickness of the protective film 30 can be increased compared to when the second silicon oxide film 36 is not provided, so that this can be suppressed. The second silicon oxide film 36 is disposed on the outermost side of the protective film 30. The second silicon oxide film 36 has a first surface which is the surface on the light emitting side facet 14 side, and a second surface which is the surface located on the opposite side to the first surface. The second surface of the second silicon oxide film 36 is in contact with a sealing medium that seals the nitride semiconductor laser element 10. The sealing medium is, for example, a gas containing oxygen. The first surface of the second silicon oxide film 36 is, for example, a surface in contact with the second Al-containing film 35. 4, when a portion of the protective film 30 is provided on the upper surface side and / or the lower surface side of the nitride semiconductor laminate, the films constituting the protective film 30 other than the second silicon oxide film 36 can be covered with the second silicon oxide film 36. This can further reduce the possibility that the protective film 30 will deteriorate due to operation of the nitride semiconductor laser element 10. Of the films constituting the protective film 30, only the second silicon oxide film 36 may be in contact with the sealing medium that seals the nitride semiconductor laser element 10. The second silicon oxide film 36 may be made of the same material as the first silicon oxide film 34. The second silicon oxide film 36 is a film made of, for example, SiO2. The second silicon oxide film 36 is preferably a film containing an amorphous structure, which can improve the adhesion with the second Al-containing film 35. The thickness of the second silicon oxide film 36 can be made greater than the thickness of the first silicon oxide film 34. This can further improve the protective performance of the second silicon oxide film 36. The thickness of the second silicon oxide film 36 may be greater than the thickness of the first Al-containing film 33. For example, the thickness of the second silicon oxide film 36 can be set within a range of ±5% of λ / 2n6, where n6 is the refractive index of the second silicon oxide film 36 at the oscillation wavelength λ. The second silicon oxide film 36 can be formed by a known method such as a sputtering method or an ECR sputtering method.

[0030] By virtue of having such a configuration, the nitride semiconductor laser device 10 of this embodiment can reduce the probability of occurrence of facet damage and can achieve a longer life.

[0031] (Protective film 40) A protective film 40 (second protective film) is provided on the light reflecting side end face 15. The protective film 40 has a film structure different from or the same as that of the protective film 30 on the light emitting side end face 14 side. The reflectance of the protective film 40 for the oscillation wavelength of the nitride semiconductor laser element 10 is higher than the reflectance of the protective film 30 for the oscillation wavelength of the nitride semiconductor laser element 10. The protective film 40 on the light reflecting end face 15 side may have the same film as the multilayer film of the first film 31, the second film 32, and the first Al-containing film 33 described above. The protective film 40 may be a film made of an oxide of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B, Ti, etc. (particularly, Al2O3, SiO2, Nb2O5, TiO2, ZrO2, etc.), a nitride (particularly, AlN, AlGaN, BN, etc.), or a fluoride, or a combination of two or more of these. When the protective film 40 is formed as the multilayer film of the first film 31, the second film 32, and the first Al-containing film 33, it may be formed with a different thickness from the protective film 30 on the light emitting end face 14 side. The protective film 40 is preferably formed of a material that is transparent and / or reflective to the oscillation wavelength of the nitride semiconductor laser element 10. The protective film 40 may be a single layer or a multilayer.

[0032] For example, the protective film 40 on the light-reflecting end face 15 may be a laminated film of an oxide of Si and an oxide of Zr, a laminated film of an oxide of Al and an oxide of Zr, a laminated film of an oxide of Si and an oxide of Ti, a laminated film of an oxide of Al, an oxide of Si and an oxide of Zr, a laminated film of an oxide of Si, an oxide of Ta and an oxide of Al, etc. The lamination period, etc., can be adjusted appropriately according to the desired reflectance. The thickness of the protective film 40 is not particularly limited, and may be, for example, 100 nm to 4000 nm, 300 nm to 3000 nm, or 500 nm to 2000 nm. For example, the thickness of the protective film 40 is greater than the thickness of the protective film 30.

[0033] The protective film 40 is, for example, a multilayer film. The multilayer film can have a structure in which films with relatively low refractive index and films with relatively high refractive index are alternately stacked. The film in contact with the light reflecting side end face 15 of the multilayer film may be a film with a relatively low refractive index or a film with a relatively high refractive index. As shown in FIG. 5, the protective film 40 can have a first portion 41 arranged in contact with the light reflecting side end face 15 and a second portion 42 arranged in contact with the first portion 41. FIG. 5 is a partial enlarged view showing an example of the protective film 40 on the light reflecting side end face 15 side. The thickness of the protective film 40 is preferably ±5% of an odd multiple of λ / 4n, and more preferably an odd multiple of λ / 4n. This can reduce the probability of optical damage occurring at the light reflecting side end face 15 when the nitride semiconductor laser element 10 is driven. Here, λ is the oscillation wavelength of the nitride semiconductor laser element 10, and n is the refractive index of each film at the oscillation wavelength λ. The thickness of the protective film 40 refers to the length in a direction parallel to the main surface of the active layer 13. The second portion 42 is formed by alternately arranging high-refractive index films 424 and low-refractive index films 425. The first portion 41 is made of one or more films. The film in the first portion 41 that contacts the second portion 42 has a refractive index different from both the high-refractive index film 424 and the low-refractive index film 425. By combining the first portion 41 and the second portion 42, light can be reflected at the interface between the first portion 41 and the second portion 42, and the reflectance of the protective film 40 can be improved. This can improve the optical output of the nitride semiconductor laser element 10. The distance from the light reflecting side end face 15 to the interface between the first portion 41 and the second portion 42 is preferably 50 nm or more and 200 nm or less. This can further improve the reflectance of the protective film 40, and further improve the optical output of the nitride semiconductor laser element 10. Note that the distance here refers to the shortest distance. The protective film 40 may be composed of only the first portion 41 and the second portion 42, or may further include another film.

[0034] The first portion 41 is preferably a multilayer structure having a film with a relatively low refractive index and a film with a high refractive index. This can further improve the reflectance of the protective film 40. For example, the film with a relatively low refractive index in the first portion 41 and the high refractive index film 424 in the second portion 42 are in contact with each other. Alternatively, the film with a relatively high refractive index in the first portion 41 and the low refractive index film 425 in the second portion 42 may be in contact with each other. The film in contact with the first portion 41 in the second portion 42 is preferably a film having a refractive index higher than that of the film in contact with the second portion 42 in the first portion 41, and more preferably a film having a refractive index higher than that of any of the films constituting the first portion 41. This can further improve the reflectance of the protective film 40. The low refractive index film 425 in the second portion 42 can be, for example, a silicon oxide film (for example, a SiO2 film). The high refractive index film 424 in the second portion 42 can be, for example, a tantalum oxide film (for example, Ta2O5).

[0035] The first portion 41 may have a first film 411, a second film 412, and a third film 413. The first portion 41 may have, in order from the light reflecting side end face 15 side, a crystalline first film 411 containing aluminum and / or gallium and oxygen, a crystalline second film 412 made of a nitride film, and a third film 413 containing aluminum and oxygen. The first film 411 may adopt the material, thickness, formation method, etc. described for the first film 31. The second film 412 may adopt the material, thickness, formation method, etc. described for the second film 32. The third film 413 may adopt the material, thickness, formation method, etc. described for the first Al-containing film 33. Since the first portion 41 is a portion in contact with the light reflecting side end face 15, by having such a first film 411, second film 412, and third film 413, the same effect as the protective film 30 can be expected. The first film 411 may be disposed in contact with the light reflecting side end face 15. The first film 411, the second film 412, and the third film 413 may each have a thickness of λ / 4n or less. This allows the interface between the first portion 41 and the second portion 42 to be disposed relatively close to the light reflecting side end face 15, thereby further improving the reflectance of the protective film 40 and further improving the optical output of the nitride semiconductor laser device 10. For example, the first portion 41 is composed of only the first film 411, the second film 412, and the third film 413.

[0036] (Substrate 16) The substrate 16 may be an insulating substrate or a conductive substrate. For example, a nitride semiconductor substrate made of GaN or the like can be used as the substrate 16. The first main surface of the substrate 16 on which the semiconductor layer is formed can be a C-plane, an R-plane, an M-plane, or the like, for example a C-plane. The first main surface and / or a second main surface opposite to the first main surface can have an off angle of 0° or more and 10° or less. The thickness of the substrate 16 can be 10 μm or more and 10 mm or less.

[0037] (embedded film 18, first electrode 17, second electrode 19, pad electrode 20) In the nitride semiconductor laser device 10, a buried film 18 can be provided on the upper surface of the second nitride semiconductor layer 12, for example, on the side surface of the ridge 12a and on the upper surface of the second nitride semiconductor layer 12 continuing from the side surface of the ridge 12a. The embedded film 18 is preferably formed of a material having a smaller refractive index than the second nitride semiconductor layer 12. Examples of the embedded film 18 include a single layer film or a multilayer film of an insulating film such as an oxide, nitride, or oxynitride of Zr, Si, V, Hf, Ta, Al, Ce, In, Sb, Zn, or the like. The embedded film 18 can be formed by a method known in the art, which is exemplified as the method for forming the first film 31.

[0038] A first electrode 17 can be provided on the lower surface of the first nitride semiconductor layer 11, for example, on the lower surface of the substrate 16 when a substrate 16 is provided. When the substrate 16 is a semiconductor substrate, the substrate 16 has the same conductivity type as the first nitride semiconductor layer 11. The first electrode 17 is provided, for example, over almost the entire lower surface of the substrate 16. A second electrode 19 may be provided on the upper surface of the second nitride semiconductor layer 12, for example, on the upper surface of the ridge 12a, and a pad electrode 20 may be further provided thereon. The first electrode 17 and the second electrode 19 can be formed of a single layer or a multilayer film of a conductive oxide containing at least one selected from metals or alloys such as Ni, Rh, Cr, Au, W, Pt, Ti, Al, and Pd, Zn, In, and Sn. Examples of the conductive oxide include ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), and GZO (Gallium-doped Zinc Oxide). The thickness of the electrodes may be any thickness that can function as an electrode of a semiconductor laser element. For example, the thickness may be 0.1 μm or more and 2 μm or less.

[0039] The first electrode 17 and the second electrode 19 may be provided on the first main surface side and the second main surface side, respectively, of the nitride semiconductor stack, or both may be provided on either the first main surface side or the second main surface side. The embedded film 18, the first electrode 17, the second electrode 19, and the pad electrode 20 may be separated from or in contact with the protective film 30. The embedded film 18, the first electrode 17, the second electrode 19, and the pad electrode 20 may cover the protective film 30, or may be covered by the protective film 30. The embedded film 18 and the second electrode 19 are preferably covered by the protective film 30. This can prevent the embedded film 18 and the second electrode 19 from peeling off.

[0040] (Example) As the nitride semiconductor laser device 10 shown in FIGS. 1A to 1D, a gallium nitride-based semiconductor laser device with a peak oscillation wavelength of about 445 nm was fabricated. An MOCVD apparatus was used to fabricate an epitaxial wafer that would become the nitride semiconductor laser element 10. Trimethylgallium (TMG), triethylgallium (TEG), trimethylaluminum (TMA), trimethylindium (TMI), ammonia (NH3), silane gas, and bis(cyclopentadienyl)magnesium (Cp2Mg) were used as appropriate as raw materials. An n-side semiconductor layer as a first nitride semiconductor layer 11, an active layer 13, and a p-side semiconductor layer as a second nitride semiconductor layer 12 were grown on an n-type GaN substrate (substrate 16) having a C-plane as a growth surface, and a stripe-shaped ridge 12a having a length of 1200 μm in a direction parallel to the cavity length was formed on the surface of the p-side semiconductor layer. Next, a p-electrode made of ITO (200 nm) was formed as a second electrode 19 on the upper surface of the p-side semiconductor layer, and a buried film 18 made of SiO2 was formed on the side surface of the ridge 12a and on the upper surface of the p-side semiconductor layer outside the ridge 12a. The buried film 18 was formed so that a part of it partially covered the p-electrode. A pad electrode 20 was formed in succession on the p-electrode using Ni (8 nm) / Pd (200 nm) / Au (400 nm) / Pt (200 nm) / Au (700 nm). Thereafter, substrate 16 was polished from the surface opposite to the growth surface of first nitride semiconductor layer 11 so that the thickness was 80 μm, and an n-electrode made of Ti (8 nm) / Pt (100 nm) / Au (300 nm) was formed on the polished surface as first electrode 17. Next, substrate 16 was cleaved into bars from the surface on which the n-electrode was formed, and the cleaved surfaces were made into resonator surfaces, that is, light-emitting end face 14 and light-reflecting end face 15. The light-emitting end face 14 and the light-reflecting end face 15 of the obtained bar were subjected to surface treatment by exposing them to oxygen plasma using an ECR sputtering device. -7 m 3 The mixture was treated with microwaves at 500 W for 10 minutes at a temperature of 100 °C / s. Thereafter, an Al target was used for the light-emitting end surface 14, and the flow rate of Ar was set to 5×10 -7 m 3 / s, oxygen flow rate is 1.67×10 -7 m 3 A first film 31 made of Al2O3 was formed at 1000 s and a microwave of 500 W. The oxygen gas was changed to nitrogen gas, and a second film 32 made of AlN was similarly formed. Next, the nitrogen gas was changed to oxygen gas, and a first Al-containing film 33 made of Al2O3 was similarly formed. Next, a first silicon oxide film 34 made of SiO2, a second Al-containing film 35 made of Al2O3, and a second silicon oxide film 36 made of SiO2 were formed. In this way, a protective film 30 was formed. The oxygen flow rate during the formation of the first film 31 was 1.67×10 -7 m 3 / s, and the oxygen flow rate during the formation of the first Al-containing film 33 was 8.33×10 -8 m 3 On the light reflecting end face 15, a protective film 40 including a multi-layer structure in which SiO2 and Ta2O5 are alternately laminated multiple times was formed. Thereafter, the bar was cut in a direction perpendicular to the cleavage plane to obtain the nitride semiconductor laser device 10 of the example. In the nitride semiconductor laser element 10 of the example and the nitride semiconductor laser elements of the comparative example and reference examples 1 to 4, the protective film 30 was formed to have the configuration shown in Table 1. In each of these nitride semiconductor laser elements, the reflectance of the protective film 30 for the oscillation wavelength of the nitride semiconductor laser element 10 was about 15%.

[0041] [Table 1]

[0042] Eight pieces each of the nitride semiconductor laser element 10 of the embodiment and the nitride semiconductor laser elements of the comparative example and reference examples 1 to 4 were fabricated, and the optical density was approximately 50 MW / cm 2 A life test was performed by continuously oscillating at 400 rpm for about 7 months, and the number of sudden deaths was measured. The test was terminated when the number of sudden deaths was confirmed to be more than half, i.e., when at least five sudden deaths were confirmed. As a result, the test was continued until the end of the test period in the Example and Reference Example 4, while in the Comparative Example, Reference Example 1, Reference Example 2, and Reference Example 3, in that order, more than half of the lasers had suddenly died before the end of the test period, and the test was terminated. The number of sudden deaths at the end of the test period was 1 in the Example and 2 in Reference Example 4. In the nitride semiconductor laser element 10 of the Example and the nitride semiconductor laser elements of the Comparative Example and Reference Examples 1 to 4, the time from the start of the life test until the first laser died suddenly was the longest in the nitride semiconductor laser element 10 of the Example.

[0043] From these results, it was confirmed that the occurrence of damage to the facet of the nitride semiconductor laser element 10 can be reduced by providing the first film 31, the second film 32, the first Al-containing film 33, the first silicon oxide film 34, the second Al-containing film 35, and the second silicon oxide film 36. It was also confirmed that this makes it possible to extend the life of the nitride semiconductor laser element 10.

[0044] Through the contents described so far in this specification, the following technical matters are disclosed. (Item 1) A semiconductor device comprising: a first nitride semiconductor layer of a first conductivity type; a second nitride semiconductor layer of a second conductivity type different from the first conductivity type; an active layer disposed between the first nitride semiconductor layer and the second nitride semiconductor layer; a light emitting side end face and a light reflecting side end face intersecting with a surface of the active layer on the second nitride semiconductor layer side; and a protective film provided on the light emitting side end face; the protective film includes, in order from the light emitting end face side, a first film made of an oxide film containing aluminum and / or gallium, a second film made of a nitride film, a first Al-containing film containing aluminum and oxygen, a first silicon oxide film, a second Al-containing film containing aluminum and oxygen, and a second silicon oxide film; The second silicon oxide film is disposed on the outermost side of the protective film for the nitride semiconductor laser element. (Section 2) 2. The nitride semiconductor laser element according to item 1, wherein the first Al-containing film and the second Al-containing film are oxide films containing aluminum. (Section 3) 3. The nitride semiconductor laser element according to item 1 or 2, wherein the first Al-containing film and the second Al-containing film are films having an amorphous structure or films including an amorphous structure and a crystalline structure. (Section 4) a thickness of the first Al-containing film is greater than a thickness of the second Al-containing film; 4. The nitride semiconductor laser element according to any one of items 1 to 3, wherein a thickness of the first silicon oxide film is smaller than a thickness of the second silicon oxide film. (Section 5) 5. The nitride semiconductor laser element according to any one of items 1 to 4, wherein the first film and the second film are crystalline films. (Section 6) 6. The nitride semiconductor laser device according to any one of items 1 to 5, wherein the first film has a thickness of less than 10 nm. (Section 7) 7. The nitride semiconductor laser element according to any one of items 1 to 6, wherein an axial orientation of a crystal in a region of the second film adjacent to the active layer is the same as an axial orientation of a crystal in a region of the second film adjacent to the first nitride semiconductor layer and / or a region of the second film adjacent to the second nitride semiconductor layer. [Explanation of symbols]

[0045] 10. Nitride semiconductor laser element 11 First nitride semiconductor layer 12 Second nitride semiconductor layer 12a Ridge 13 Active layer 14 Light output side end face 14a Light exit surface 15 Light reflecting side end face 16 Substrate 17 1st electrode 18 Embedding Membrane 19 2nd electrode 20 Pad Electrode 30 Protective film 31 1st membrane 32 Second membrane 33 1st Al-containing film 34 First silicon oxide film 35 2nd Al-containing film 36 Second silicon oxide film 40 Protective film 41 Part 1 42 Part 2 411 1st membrane 412 Second membrane 413 Third membrane 424 High refractive index film 425 Low refractive index film

Claims

1. a first nitride semiconductor layer of a first conductivity type, a second nitride semiconductor layer of a second conductivity type different from the first conductivity type, an active layer disposed between the first nitride semiconductor layer and the second nitride semiconductor layer, a light emitting side end face and a light reflecting side end face intersecting with a surface of the active layer on the second nitride semiconductor layer side, and a protective film provided on the light emitting side end face, the protective film includes, in order from the light emitting end face side, a first film made of an oxide film containing aluminum and / or gallium, a second film made of a nitride film, a first Al-containing film containing aluminum and oxygen, a first silicon oxide film, a second Al-containing film containing aluminum and oxygen, and a second silicon oxide film; The second silicon oxide film is disposed on the outermost side of the protective film of the nitride semiconductor laser element.

2. The nitride semiconductor laser device according to claim 1 , wherein the first Al-containing film and the second Al-containing film are oxide films containing aluminum.

3. 2. The nitride semiconductor laser device according to claim 1, wherein the first Al-containing film and the second Al-containing film are films having an amorphous structure or films including an amorphous structure and a crystalline structure.

4. a thickness of the first Al-containing film is greater than a thickness of the second Al-containing film; The nitride semiconductor laser device according to claim 1 , wherein a thickness of said first silicon oxide film is smaller than a thickness of said second silicon oxide film.

5. 2. The nitride semiconductor laser device according to claim 1, wherein the first film and the second film are crystalline films.

6. The nitride semiconductor laser device according to claim 1 , wherein the first film has a thickness of less than 10 nm.

7. The nitride semiconductor laser element according to any one of claims 1 to 6, wherein an axial orientation of crystals in a region of the second film adjacent to the active layer is the same as an axial orientation of crystals in a region of the second film adjacent to the first nitride semiconductor layer and / or a region of the second film adjacent to the second nitride semiconductor layer.

Images