Nitride semiconductor light emitting device

Abstract

To provide a nitride semiconductor light emitting element having improved reliability.SOLUTION: A nitride semiconductor light emitting element 10 includes a nitride semiconductor 100 having two resonator surfaces 160, 161 facing each other, and a dielectric multilayer film laminated at least one resonator surface of the two resonator surfaces 160, 161. For example, the dielectric multilayer film 200 laminated on the resonator surface 160 has a dielectric film 201 laminated on the resonator surface 160 and a dielectric film 202 laminated on the dielectric film 201. The dielectric film 201 comprises an aluminum oxynitride. The dielectric film 202 comprises an aluminum oxide. The dielectric film 201 is a crystal film. The dielectric film 201 is added with at least one element of yttrium or lanthanum. The dielectric film 202 is added with at least one element of yttrium or lanthanum.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to nitride semiconductor light emitting devices. [Background technology]

[0002] Conventionally, a film has been formed on an end face (cavity face) of a nitride semiconductor that emits light such as laser light in order to resonate light inside or outside the nitride semiconductor and appropriately emit light from the nitride semiconductor light-emitting element (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4799339 [Patent Document 2] Patent No. 5042609 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-119540 [Patent Document 4] International Publication No. 2009 / 147853 Summary of the Invention [Problem to be solved by the invention]

[0004] BACKGROUND ART It is desirable to improve the reliability of a nitride semiconductor light emitting device that includes a nitride semiconductor and a film formed on an end face of the nitride semiconductor.

[0005] The present disclosure provides a nitride semiconductor light emitting device with improved reliability. [Means for solving the problem]

[0006] A nitride semiconductor light-emitting element according to one embodiment of the present disclosure includes a nitride semiconductor having two resonator facets facing each other, and a dielectric multilayer film having a first dielectric film stacked on at least one of the two resonator facets and a second dielectric film stacked on the first dielectric film, wherein the first dielectric film is made of aluminum oxynitride, the second dielectric film is made of aluminum oxide, the first dielectric film is a crystalline film, and the first dielectric film is doped with at least one of yttrium and lanthanum, and the second dielectric film is doped with at least one of yttrium and lanthanum. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a nitride semiconductor light emitting device with improved reliability. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light-emitting device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing the configuration of a nitride semiconductor according to the embodiment. [Figure 4] FIG. 4 is a table showing the configuration of the nitride semiconductor according to the embodiment. [Figure 5] FIG. 5 is a table showing the configuration of the dielectric multilayer film according to the embodiment. [Figure 6] FIG. 6 is a graph showing the wavelength dependency of the reflectance at the cavity facet on the light-emitting side of the nitride semiconductor light-emitting element according to the embodiment. [Figure 7] FIG. 7 is a table showing the configuration of the dielectric multilayer film according to the embodiment. [Figure 8] FIG. 8 is a graph showing the wavelength dependency of the reflectance at the cavity facet on the light reflecting side of the nitride semiconductor light emitting element according to the embodiment. [Figure 9]FIG. 9 is a graph showing the optical properties of AlON. [Figure 10] FIG. 10 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to the embodiment. [Figure 11] FIG. 11 is a graph showing the optical properties of YAlON at 405 nm. [Figure 12] FIG. 12 is a graph showing the optical properties of YAl2O3 at 405 nm. [Figure 13] FIG. 13 is a diagram showing a configuration of a light emitting device according to an embodiment. [Figure 14] FIG. 14 is a graph showing a first example of the reflection spectrum of the dielectric multilayer film according to the embodiment. [Figure 15] FIG. 15 is a graph showing a second example of the reflection spectrum of the dielectric multilayer film according to the embodiment. [Figure 16] FIG. 16 is a graph showing a third example of the reflection spectrum of the dielectric multilayer film according to the embodiment. [Figure 17] FIG. 17 is a diagram showing another example of the configuration of the light emitting device according to the embodiment. [Figure 18] FIG. 18 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to the first modification of the embodiment. [Figure 19] FIG. 19 is a diagram showing a TEM image of the nitride semiconductor light-emitting element according to Comparative Example 1. As shown in FIG. [Figure 20] FIG. 20 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to the second modification of the embodiment. [Figure 21] FIG. 21 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to the third modification of the embodiment. [Figure 22] FIG. 22 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light-emitting device according to Comparative Example 2. As shown in FIG. [Figure 23] FIG. 23 is a diagram showing a TEM image of the nitride semiconductor light-emitting element according to Comparative Example 2. As shown in FIG. [Figure 24] FIG. 24 is a view showing a TEM image of the nitride semiconductor light-emitting element according to Comparative Example 3. As shown in FIG. [Figure 25]FIG. 25 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light-emitting device according to Comparative Example 3. As shown in FIG. [Figure 26] FIG. 26 is a diagram showing a TEM image of the nitride semiconductor light-emitting element according to Comparative Example 3. As shown in FIG. [Figure 27] FIG. 27 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light-emitting device according to Comparative Example 4. As shown in FIG. [Figure 28] FIG. 28 is a diagram showing a TEM image of the nitride semiconductor light-emitting element according to Comparative Example 4. As shown in FIG. [Figure 29] FIG. 29 is a diagram showing the reflectance of a dielectric multilayer film relative to the state of the dielectric film. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) In recent years, there has been an increasing need for high-power nitride semiconductor light-emitting devices in fields such as laser processing and LDI (Laser Direct Imaging). Furthermore, in recent years, due to the diversification of materials used in laser processing and the miniaturization and generalization of LDI, there has been a demand for shorter wavelengths of light (e.g., laser light) emitted by nitride semiconductor light-emitting devices. To obtain high-power light, wavelength multiplexing techniques are used to combine multiple laser beams with different wavelengths. Even when external resonance techniques and wavelength multiplexing techniques are used to output laser light of a specific wavelength, high-quality light (e.g., light with stable optical characteristics such as optical output and spot shape) is still required. Therefore, from the viewpoint of wavelength control and ease of wavelength multiplexing, it is required that the wavelength of light output (emitted) from nitride semiconductor light-emitting devices be stable.

[0010] In view of the above requirements, the film (dielectric film) provided on the facet of the nitride semiconductor is required to be able to withstand high-power light, be able to withstand light in the ultraviolet region, and be able to maintain low reflectance at the facet on the light-emitting side, so that its optical properties, such as transmittance, reflectance, and refractive index, are not easily changed by light.

[0011] FIG. 25 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light emitting device 10A according to Comparative Example 3. As shown in FIG.

[0012] The nitride semiconductor light emitting device 10A includes, for example, a nitride semiconductor 100 and a dielectric multilayer film 200A provided on the light emitting end face of the nitride semiconductor 100.

[0013] Dielectric multilayer film 200A includes, in order from cavity facet 160, which is the light-emitting end face of nitride semiconductor 100, dielectric film 206 made of SiN or SiON, dielectric film 201A made of AlON, dielectric film 202A made of Al2O3, dielectric film 203A made of AlON, dielectric film 204A made of Al2O3, and dielectric film 205 made of SiO2. The thicknesses of dielectric films 206, 201A to 204A, and 205 are, respectively, 3 nm for dielectric film 206, 20 nm for dielectric film 201A, 13 nm for dielectric film 202A, 11 nm for dielectric film 203A, 160 nm for dielectric film 204A, and 57 nm for dielectric film 205. Furthermore, the dielectric films 202A, 204A, and 205 are each amorphous (when formed), and the dielectric films 201A and 203A are each a dielectric film that includes at least a crystalline region.

[0014] Fig. 26 is a diagram showing an example of a TEM image of a nitride semiconductor light emitting device 10A according to Comparative Example 3. Fig. 26 is a TEM image taken after the nitride semiconductor light emitting device 10A, which emits light with a peak wavelength of 405 nm, has been driven for 300 hours at 1.4 W (@25°C) using a CW (Continuous Wave) source. In this example, the ridge width of the nitride semiconductor 100 is 7 µm.

[0015] As shown in FIG. 26, the amorphous dielectric film 204A is partially crystallized.

[0016] FIG. 27 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light-emitting device 1000 according to Comparative Example 4. As shown in FIG.

[0017] The nitride semiconductor light emitting device 1000 includes, for example, a nitride semiconductor 100 having a light emitting layer 120 that emits light, and a dielectric multilayer film 2000 provided on the cavity facets 160 of the nitride semiconductor 100 .

[0018] Dielectric multilayer film 2000 includes, in order from the cavity facet 160 side of nitride semiconductor 100, dielectric film 2001 made of AlON, dielectric film 2002 made of AlN, dielectric film 2003 made of Al2O3, dielectric film 2004 made of AlN, dielectric film 2005 made of SiO2, dielectric film 2006 made of Al2O3, and dielectric film 2007 made of SiO2. Dielectric films 2001 to 2004 have thicknesses of 3 nm for dielectric film 2001, 18 nm for dielectric film 2002, 13 nm for dielectric film 2003, and 11 nm for dielectric film 2004. Dielectric films 2003 and 2005 to 2007 are each amorphous (as deposited), and dielectric films 2001, 2002, and 2004 each include at least a crystalline region.

[0019] Fig. 28 is a diagram showing a TEM image of the nitride semiconductor light-emitting element 1000 according to Comparative Example 4. Fig. 28 is a TEM image after the nitride semiconductor light-emitting element 1000, which emits light with a peak wavelength of 405 nm, has been driven for 8,500 hours with a pulse width of 200 ns (duty ratio of 50%) and 1.2 W (@50°C).

[0020] As shown in FIG. 28, the amorphous dielectric film 2006 has been partially crystallized, and peeling (gaps) that were not originally present have occurred between the dielectric films 2005 and 2006.

[0021] In this way, when the dielectric multilayer film 2000 provided on the cavity facet 160 of the nitride semiconductor 100 is amorphous, the dielectric films may react with each other or crystallize, causing a change in volume of the dielectric film, which may result in peeling (film peeling) between the dielectric films or between the nitride semiconductor and the dielectric film.

[0022] FIG. 29 is a diagram showing the reflectance of dielectric multilayer film 2000 in relation to the states of dielectric films 2003 and 2006. Note that the "third layer" in FIG. 29 refers to the third layer, counting the dielectric films included in dielectric multilayer film 2000 from the cavity facet 160 side of nitride semiconductor 100, i.e., dielectric film 2003 (Al2O3 film). Also, the "sixth layer" in FIG. 29 refers to the sixth layer, counting the dielectric films included in dielectric multilayer film 2000 from the cavity facet 160 side of nitride semiconductor 100, i.e., dielectric film 2006 (Al2O3 film). Also, n in FIG. 29 refers to the refractive index of dielectric films 2003 and 2006. Specifically, the refractive index of amorphous dielectric films 2003 and 2006 is 1.65, and the refractive index of crystallized dielectric films 2003 and 2006 is 1.76. 50% crystallization means that one half of the dielectric film 2006 (e.g., the portion located on the resonator facet 160 side) is amorphous, and the other half (e.g., the portion located on the opposite side from the resonator facet 160 side) is crystallized.

[0023] As shown in Figure 29, the reflectance of the dielectric multilayer film 2000 differs depending on whether the dielectric films 2003 and 2006 are amorphous or crystallized. The rate of change in reflectance at 450 nm is a maximum of 1 / 5 (a reflectance difference of 3% for a reflectance of approximately 15%), but increases as the wavelength becomes shorter. The rate of change in reflectance at 405 nm is a maximum of 1 / 3 (a reflectance difference of 2% for a reflectance of approximately 6%).

[0024] As described above, for example, when an amorphous dielectric multilayer film is crystallized by light emitted from a nitride semiconductor, film peeling occurs, or even if film peeling does not occur, optical properties such as reflectance change, which may result in changes in characteristics such as the output of light emitted by the nitride semiconductor light-emitting element. For example, if the nitride semiconductor light-emitting element is an element that emits laser light by external resonance, crystallization of the dielectric multilayer film during operation gradually reduces the gain due to external resonance. For this reason, the dielectric multilayer film is required to have optical properties that are less likely to change (i.e., stable). In other words, nitride semiconductor light-emitting elements are desired to have higher reliability than conventional devices.

[0025] The structure disclosed in Patent Document 1 has a problem in that it is difficult to control the reflectance because the amorphous dielectric film is a single layer.

[0026] The structure disclosed in Patent Document 2 has a problem in that the refractive index of the crystalline dielectric film changes as the film oxidizes over time during operation. Also, crystalline dielectric films have a problem in that the adhesion between the cavity facets of the nitride semiconductor and the dielectric film decreases due to dangling bonds formed at the interface (for example, film peeling becomes more likely to occur).

[0027] The structure disclosed in Patent Document 3 has a problem in that the amorphous dielectric film made of an Al compound, which is located in the second layer from the cavity facet in the dielectric multilayer film, can be altered (crystallized, etc.) by absorbing light, etc.

[0028] The structure disclosed in Patent Document 4 uses a dielectric film made of YAlN crystal, and by adding Y, which has a large bond energy with oxygen, the oxygen barrier property (oxygen trapping property) is improved compared to AlN. Therefore, the dielectric film made of YAlN has a problem in that the refractive index of the dielectric film changes due to oxidation over time.

[0029] In view of the above problems, the present application provides a nitride semiconductor light emitting device with improved reliability.

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, and the arrangement and connection of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0031] Furthermore, each figure is a schematic diagram and is not necessarily an exact representation. Therefore, the scales and the like do not necessarily match in each figure. In each figure, the same reference numerals are used to denote substantially the same components, and redundant explanations will be omitted or simplified.

[0032] In this specification, the terms "above" and "below" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in the stacked structure of nitride semiconductors. Furthermore, the terms "above" and "below" are applied not only to the case where two components are arranged with a gap between them and another component exists between the two components, but also to the case where two components are arranged in contact with each other.

[0033] In this specification and drawings, the X-axis, Y-axis, and Z-axis represent the three axes of a three-dimensional Cartesian coordinate system. In each embodiment, the Z-axis direction is defined as the vertical direction, and the direction perpendicular to the Z-axis (the direction parallel to the XY plane) is defined as the horizontal direction. The positive direction of the Z-axis is defined as the vertically upward direction.

[0034] In addition, in this specification, the term "laminated" means that two layers are arranged in a layered manner, and is used whether the two layers (or films) are in contact or not.

[0035] In this specification, the lamination direction in the laminated structure of the nitride semiconductor is the Z-axis direction, and the lamination direction in the multilayer film structure of the dielectric multilayer film is the X-axis direction.

[0036] (Embodiment) [structure] <Nitride semiconductor light-emitting element> FIG. 1 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light-emitting device 10 according to an embodiment.

[0037] The nitride semiconductor light emitting element 10 is a nitride semiconductor light emitting element that emits light (more specifically, laser light).

[0038] The nitride semiconductor light emitting element 10 comprises a nitride semiconductor 100 that emits light (more specifically, laser light), and dielectric multilayer films 200, 300 provided in contact with cavity facets 160, 161 of the nitride semiconductor.

[0039] The cavity facet 160 is a so-called front end face from which light is emitted, and has a dielectric multilayer film (first dielectric multilayer film) 200 disposed thereon.

[0040] Cavity facet 161 is a so-called rear end face that reflects light, and dielectric multilayer film (first dielectric multilayer film) 300 is disposed on it.

[0041] For example, light resonated between cavity facets 160 and 161 is emitted from cavity facets 160. Alternatively, when nitride semiconductor light emitting element 10 emits laser light by external resonance, light resonated between cavity facets 161 and an optical system such as a half mirror (for example, a coupler 450 shown in FIG. 13 , which will be described later) is emitted from cavity facets 160.

[0042] <Nitride semiconductors> The nitride semiconductor 100 is a nitride-based semiconductor having two cavity facets 160 and 161 facing each other. The nitride semiconductor 100 is, for example, a stacked body made up of multiple semiconductor layers. In this embodiment, the nitride semiconductor 100 is formed of a gallium nitride-based material, which is an example of a nitride material. As a result, for example, by appropriately setting the current and voltage applied to the nitride semiconductor 100, the nitride semiconductor 100 can be realized with optical properties that allow it to emit laser light having a wavelength in a band of approximately 370 nm to 430 nm and an optical output of W class (e.g., 1 W or more). The wavelength of the light emitted from the nitride semiconductor 100 (i.e., the oscillation wavelength of the nitride semiconductor 100) may be set arbitrarily, but is, for example, 430 nm or less. More specifically, the nitride semiconductor 100 emits laser light having a peak wavelength of 430 nm or less.

[0043] For example, nitride semiconductor 100 has a hexagonal crystal structure. At least one of cavity facets 160 and 161 is an m-plane of the hexagonal crystal structure. In this embodiment, cavity facets 160 and 161 are both m-planes.

[0044] It should be noted that the optical characteristics of the nitride semiconductor light-emitting element 10 are not limited to those described above. For example, the nitride semiconductor light-emitting element 10 may be formed so as to be able to output light of a wavelength band by arbitrarily setting the input current, input power, stripe width (ridge width), and cavity length to the nitride semiconductor 100.

[0045] Furthermore, the nitride semiconductor 100 may be a so-called single emitter having one ridge portion (emitter), or may be a so-called multi-emitter having a plurality of ridge portions (for example, about 60).

[0046] Fig. 2 is a diagram showing a TEM image of the nitride semiconductor light-emitting element 10 according to the embodiment. Fig. 3 is a cross-sectional view showing the configuration of the nitride semiconductor 100 according to the embodiment. Fig. 4 is a table showing the configuration of the nitride semiconductor 100 according to the embodiment.

[0047] As shown in FIG. 3, the nitride semiconductor 100 includes an N-side electrode 101, a substrate 102, an N-type nitride semiconductor layer 110, a light-emitting layer 120, a P-type nitride semiconductor layer 130, a current blocking layer 141, a P-side electrode (ohmic electrode) 142, and a pad electrode 143.

[0048] The N-side electrode 101 is an electrode disposed on the lower surface of the substrate 102. The N-side electrode 101 is, for example, a laminated film in which Ti, Pt, and Au are laminated in this order from the substrate 102 side.

[0049] The substrate 102 is a plate-like member that serves as the base material of the nitride semiconductor 100. In this embodiment, the substrate 102 is an n-type GaN single crystal substrate with a thickness of 85 μm.

[0050] The N-type nitride semiconductor layer 110 is an N-type semiconductor layer disposed (that is, stacked) on the upper surface of the substrate 102.

[0051] The N-type nitride semiconductor layer 110 includes an N-clad layer 111 and an N-guide layer 112 .

[0052] The N clad layer 111 is a layer made of AlGaN and is stacked on the substrate 102. For example, the N clad layer 111 has a thickness of 3 μm and a concentration of Si, which is an n-type dopant (impurity), of 1×10 18 cm -3 The N-type AlGaN layer is

[0053] The N guide layer 112 is a layer made of GaN and is stacked on the N clad layer 111. For example, the N guide layer 112 has a film thickness of 127 nm and a Si concentration of 1×10 18 cm -3 It is made of N-type GaN.

[0054] The light emitting layer 120 is stacked on the N-type nitride semiconductor layer 110 and is a light emitting layer that emits light.

[0055] The light emitting layer 120 includes an N-side guide layer 121, an active layer 122, a P-side guide layer 123, and an intermediate layer .

[0056] The N-side guide layer 121 is a layer made of InGaN and is stacked on the N-side guide layer 112. For example, the N-side guide layer 121 is made of undoped In 0.008 Ga 0.992 It consists of N.

[0057] The active layer 122 is a layer made of InGaN and is stacked on the N-side guide layer 121. For example, the active layer 122 is made of undoped In 0.066 Ga 0.934 N and undoped In 0.008 Ga 0.992 In this embodiment, the active layer 122 is a quantum well active layer in which well layers and barrier layers are alternately stacked, and has two well layers. With such an active layer 122, the nitride semiconductor light emitting element 10 can emit blue-violet laser light with a center wavelength of approximately 405 nm.

[0058] The P-side guide layer 123 is a layer made of InGaN and is stacked on the active layer 122. For example, the P-side guide layer 123 may be made of undoped In 0.003 Ga 0.997 It consists of N.

[0059] The intermediate layer 124 is a layer made of InGaN / GaN and is stacked on the p-side guide layer 123. The intermediate layer 124 is configured, for example, so that the composition ratio of In gradually decreases from the p-side guide layer 123 side toward the top.

[0060] The P-type nitride semiconductor layer 130 is a P-type semiconductor layer stacked on the light emitting layer 120 .

[0061] The N-type nitride semiconductor layer 110, the light emitting layer 120, and the P-type nitride semiconductor layer 130 form a waveguide, which is a waveguide portion for light. The waveguide is a portion through which light is guided inside the nitride semiconductor 100. The waveguide is made up of, for example, a part of the N-type nitride semiconductor layer 110, a part of the light emitting layer 120, and a part of the P-type nitride semiconductor layer 130.

[0062] The P-type nitride semiconductor layer 130 includes an electron barrier layer 131 , a P clad layer 132 , and a contact layer 133 .

[0063] The electron barrier layer 131 is a layer made of AlGaN and is stacked on the light emitting layer 120. The electron barrier layer 131 is configured, for example, so that the Al composition ratio gradually increases upward from the light emitting layer 120 side. For example, the electron barrier layer 131 has a composition gradient in which the Al composition changes from 4% to 36%.

[0064] The P cladding layer 132 is a layer made of AlGaN and is stacked on the electron barrier layer 131. The P cladding layer 132 is made of, for example, a first layer stacked on the electron barrier layer 131, and a second layer stacked on the first layer and having a lower impurity concentration than the first layer. For example, the P cladding layer 132 has a concentration of Mg, a P-type dopant, of 2×10 18 cm -3 Al0.026 Ga 0.974 The first layer consists of N and the second layer consists of Mg with a concentration of 1×10 19 cm -3 Al 0.026 Ga 0.974 and a second layer made of N.

[0065] In this embodiment, a striped ridge portion for confining current and light is formed in the P cladding layer 132. The region of the light emitting layer 120 corresponding to the ridge portion (i.e., the region of the light emitting layer 120 located below the ridge portion) serves as a light emitting point, from which light is emitted.

[0066] The contact layer 133 is a P-type semiconductor layer that is in ohmic contact with the P-side electrode 142. The contact layer 133 is a layer made of GaN and stacked on the P-cladding layer 132. The contact layer 133 is made of, for example, a first layer stacked on the P-cladding layer 132, and a second layer stacked on the first layer and having a higher impurity concentration than the first layer. For example, the contact layer 133 has an Mg concentration of 2×10 19 cm -3 The GaN layer is made of GaN doped with the above.

[0067] The current blocking layer 141 covers the sidewalls of the ridge portion, the side surfaces of the P-type nitride semiconductor layer 130, the side surfaces of the light emitting layer 120, etc., and is an electrically insulating film such as an SiO 2 film.

[0068] The p-side electrode 142 is an ohmic electrode laminated on the contact layer 133. The p-side electrode 142 is, for example, a laminated film in which Pd (palladium) and Pt (platinum) are laminated in this order from the contact layer 133 side.

[0069] The pad electrode 143 is a pad-shaped electrode laminated on the P-side electrode 142 for receiving power supplied from the outside. The pad electrode 143 is, for example, a laminated film in which Cr (chromium) or Ti (titanium), Pt and Au (gold) are laminated in this order from the P-side electrode 142 side, and is disposed on the ridge portion and its periphery. The Cr or Ti is provided to improve adhesion between the pad electrode 143 and the P-side electrode 142.

[0070] The materials, In or Al compositions, film thicknesses, and impurity concentrations used for each layer shown in FIG. 4 are merely examples and are not limited thereto. For example, the thickness of the substrate 102 is not limited to 85 μm and may be, for example, 50 μm or more and 120 μm or less. For example, the material forming the substrate 102 is not limited to single crystal GaN and may be sapphire, SiC, or the like. Furthermore, the configuration of the active layer 122 is not limited to the above and may be a quantum well active layer in which well layers and barrier layers are alternately stacked, or may be a single quantum well active layer in which one well layer is provided with barrier layers above and below it. Furthermore, for example, the P cladding layer 132 may be a superlattice layer in which layers made of AlGaN and layers made of GaN are alternately stacked.

[0071] <Dielectric multilayer film> Dielectric multilayer films 200 and 300 are protective films disposed on cavity facets 160 and 161, respectively, of nitride semiconductor 100. Specifically, dielectric multilayer films 200 and 300 are provided to protect cavity facets 160 and 161 of nitride semiconductor 100 and to control the reflectance of light at cavity facets 160 and 161, respectively.

[0072] It is sufficient that a dielectric multilayer film is disposed on at least one of the cavity faces 160 and 161 .

[0073] Dielectric multilayer film 200 is disposed in contact with cavity facet 160, which is the facet (front facet) of nitride semiconductor 100 from which light is emitted, and is a multilayer film provided to reduce reflectance.

[0074] FIG. 5 is a table showing the configuration of the dielectric multilayer film 200 according to the embodiment.

[0075] The dielectric multilayer film 200 has, in this order from the cavity facet 160 side, a dielectric film (first dielectric film) 201, a dielectric film (second dielectric film) 202, a dielectric film (third dielectric film) 203, a dielectric film (fourth dielectric film) 204, and a dielectric film (second optical film) 205.

[0076] Dielectric film 201 is stacked on cavity facet 160 and is a film made of aluminum oxynitride doped with at least one of Y (yttrium) and La (lanthanum). In this embodiment, dielectric film 201 is a film made of YAlON. Dielectric film 201 is also a crystalline film. A crystalline film is a film in which the entire film is crystallized. In other words, dielectric film 201 is crystallized when it is formed (in other words, at the time when nitride semiconductor light emitting device 10 is manufactured).

[0077] The dielectric film 202 is laminated on the dielectric film 201 and is made of aluminum oxide to which at least one of yttrium and lanthanum is added. The aluminum oxide is AlO x (x>0), and examples thereof include AlO, Al2O3, and Al2O. In this embodiment, the dielectric film 202 is a film made of YAl2O3. The dielectric film 202 is amorphous (amorphous film).

[0078] The dielectric film 203 is stacked on the dielectric film 202 and is a film made of aluminum oxynitride to which at least one of yttrium and lanthanum is added. In this embodiment, the dielectric film 203 is a film made of YAlON. The dielectric film 203 may be a crystalline film or may be amorphous. In this embodiment, the dielectric film 203 is a film at least partially crystallized. That is, the dielectric film 203 is at least partially crystallized when it is formed (in other words, at the time when the nitride semiconductor light emitting device 10 is manufactured).

[0079] The crystals contained in the dielectric film 203 may have the same crystal structure and crystal orientation as the crystals contained in the dielectric film 201, or may differ in at least one of the crystal structure and crystal orientation. Different crystal structures refer to different so-called crystallinity, such as different atomic bonding states and atomic arrangements. For example, different crystal structures refer to different degrees of crystallization (e.g., ratios of amorphous phase to crystalline phase), different densities, different average crystal grain sizes, etc. Furthermore, different orientations refer to different predominant orientations when the dielectric film is viewed as a whole. Details of cases in which the crystals contained in the dielectric film 203 and the crystals contained in the dielectric film 201 differ in at least one of the crystal structure and crystal orientation will be described later.

[0080] Dielectric film 204 is laminated on dielectric film 203 and is a film made of aluminum oxide to which at least one of the elements yttrium and lanthanum is added. In this embodiment, dielectric film 204 is a film made of YAl2O3. Dielectric film 204 is also amorphous.

[0081] The dielectric film 205 is laminated on the dielectric film 204 and is made of silicon oxide. Silicon oxide is SiO x It is a composition expressed by (x>0), and examples thereof include SiO, SiO2, etc. In this embodiment, the dielectric film 205 is a film made of SiO2.

[0082] Dielectric film 205 (i.e., a film made of silicon oxide) may be laminated on at least one of dielectric film 201, dielectric film 202, dielectric film 203, and dielectric film 204. In this embodiment, dielectric film 205 is located at the position farthest from cavity facet 160 (i.e., the outermost film) among the multiple films (dielectric films 201 to 205) included in dielectric multilayer film 200.

[0083] Furthermore, the dielectric film 205 (that is, a film made of silicon oxide) may be stacked on at least one of the dielectric film 301, the dielectric film 302, and the dielectric film 303.

[0084] 6 is a graph showing the wavelength dependency of reflectance at the cavity facet (cavity facet 160) on the light emission side of nitride semiconductor light emitting element 10 according to the embodiment. Specifically, FIG. 6 is a graph showing the reflectance at the interface between dielectric multilayer film 200 and cavity facet 160 versus the wavelength of light.

[0085] As shown in FIG. 6, for example, the dielectric multilayer film 200 has a reflectance of 10% or less in the vicinity of 400 nm, which is considered to be the central wavelength of the light emitted by the nitride semiconductor 100.

[0086] Dielectric multilayer film 300 is disposed in contact with cavity facet 161, which is the end face (rear end face) of nitride semiconductor 100 that reflects light, and is a multilayer film provided to increase reflectance.

[0087] FIG. 7 is a table showing the configuration of the dielectric multilayer film 300 according to the embodiment.

[0088] The dielectric multilayer film 300 has, from the cavity facet 161 side, a dielectric film (first dielectric film) 301, a dielectric film (second dielectric film) 302, a dielectric film (third dielectric film) 303, and an optical interference film 310 in this order.

[0089] Dielectric film 301 is laminated on cavity facet 161 and is a film made of aluminum oxynitride doped with at least one of yttrium and lanthanum. In this embodiment, dielectric film 301 is a film made of YAlON. Dielectric film 301 is also a crystalline film.

[0090] Dielectric film 302 is laminated on dielectric film 301 and is a film made of aluminum oxide to which at least one of the elements yttrium and lanthanum is added. In this embodiment, dielectric film 302 is a film made of YAl2O3. Dielectric film 302 is also amorphous.

[0091] The dielectric film 303 is laminated on the dielectric film 302 and is a film made of aluminum oxynitride to which at least one of yttrium and lanthanum is added. In this embodiment, the dielectric film 303 is a film made of YAlON. The dielectric film 303 may be a crystalline film or may be amorphous. In this embodiment, the dielectric film 303 is a film at least partially crystallized.

[0092] The crystals contained in the dielectric film 303 may have the same crystal structure and crystal orientation as the crystals contained in the dielectric film 301, or may be different in at least one of the crystal structure and crystal orientation.

[0093] The optical interference film 310 is a multilayer film laminated on the dielectric film 303. The optical interference film 310 has two or more multilayer coating films 320. Specifically, the dielectric multilayer film 200 has a multilayer coating film 320 formed by repeatedly depositing at least two or more consecutive layers, each of which includes a first coating film 321 and a second coating film 322 laminated on the first coating film 321.

[0094] The multilayer coating film 320 has a first coating film 321 and a second coating film 322 laminated on the first coating film 321 .

[0095] The first coating film 321 is a dielectric film made of silicon oxide. In this embodiment, the first coating film 321 is a film made of SiO2.

[0096] The second coating film 322 is a dielectric film made of aluminum oxynitride to which at least one of yttrium and lanthanum is added. In this embodiment, the second coating film 322 is a film made of YAlON. The second coating film 322 may be a crystalline film or an amorphous film.

[0097] In this way, the optical interference film 310 is a multilayer film in which the first coating film 321 and the second coating film 322 are alternately laminated.

[0098] In this embodiment, the optical interference film 310 has eight multilayer coating films 320. However, the number of multilayer coating films 320 included in the optical interference film 310 is not particularly limited as long as it is plural.

[0099] Furthermore, the film located at the outermost layer of optical interference film 310 (the film located at the position farthest from cavity end face 161) may be SiO (i.e., first coating film 321). For example, in this embodiment, the 19th layer of optical interference film 310 is the outermost layer (outermost film) and second coating film 322, but optical interference film 310 may further include first coating film 321 as the 20th layer.

[0100] To obtain a high reflectance, it is desirable that the film positioned at the outermost layer be a film with a high refractive index. On the other hand, to obtain a low reflectance, it is desirable that the film positioned at the outermost layer be a film with a low refractive index. Therefore, in the dielectric multilayer film 200, a dielectric film 205 made of SiO2, which has a low refractive index, is used as the outermost film, and in the dielectric multilayer film 300, a film made of YAlON, which has a high refractive index, is used as the outermost film.

[0101] 8 is a graph showing the wavelength dependency of reflectance at the cavity facets (cavity facets 161) on the light reflecting side of nitride semiconductor light emitting element 10 according to the embodiment. Specifically, FIG. 8 is a graph showing reflectance versus light wavelength at the interface between dielectric multilayer film 300 and cavity facets 161.

[0102] 8, for example, dielectric multilayer film 300 has a reflectance of 90% or more in the range of 380 nm to 420 nm, which is considered to be the central wavelength of light emitted by nitride semiconductor 100. In other words, cavity facet 161 on which dielectric multilayer film 300 is stacked has a reflectance of, for example, 90% or more.

[0103] Also, for example, the oxygen concentration of the dielectric film 201 is not less than 2 atom % and not more than 13.4 atom %.

[0104] Fig. 9 is a graph showing the optical properties of AlON. More specifically, Fig. 9 plots the refractive index of AlON versus the oxygen flow rate (actual O flow rate (sccm)) when the Ar (argon) flow rate and N2 flow rate are fixed at 30cc and 4.9cc, respectively, during AlON deposition. When the actual O2 flow rate (sccm) is 0, the deposited film is AlN.

[0105] As shown in FIG. 9, the refractive index is stable when the oxygen flow rate is in the range of 0.1 cc to 0.5 cc. In other words, the refractive index is less likely to change with changes in the oxygen flow rate. When the oxygen flow rate is 0.3 cc, which is the central condition, the oxygen concentration of the deposited film is 13.4 atom %, and when the oxygen flow rate is 0.1 cc, the oxygen concentration of the deposited film is 2 atom %. Therefore, by adjusting the oxygen flow rate so that the oxygen concentration of the deposited film is 13.4 atom %, the change in the refractive index with changes in the oxygen flow rate can be suppressed. Furthermore, when the nitride semiconductor light-emitting element 10 is driven, the oxygen concentration in the dielectric multilayer films 200 and 300 increases during operation. Therefore, by setting the oxygen concentration of the dielectric film 201 to 13.4 atom % or less, the change in the refractive index due to the increase in oxygen concentration caused by driving can be suppressed.

[0106] The dielectric films 203, 301, and 303 may also have an oxygen concentration of 2 atom % or more and 13.4 atom % or less.

[0107] As described above, for example, dielectric films 201 and 301 contain crystals with a hexagonal crystal structure. As described above, for example, cavity faces 160 and 161 are both m-planes. Here, for example, the c-axis of the crystals contained in dielectric films 201 and 301 is perpendicular to at least one of cavity faces 160 and 161.

[0108] Fig. 10 shows a TEM image of the nitride semiconductor light-emitting device 10 according to the embodiment. Specifically, (a) of Fig. 10 is a TEM image of the nitride semiconductor light-emitting device 10. (b) of Fig. 10 shows an electron diffraction pattern at position A. (c) of Fig. 10 shows an electron diffraction pattern at position B. (d) of Fig. 10 shows an electron diffraction pattern at position C. Note that Fig. 10 shows an example in which a film was formed by ECR sputtering using an Al target in which 0.1 wt % of Y was dissolved in Al (aluminum).

[0109] As shown in (b) of Figure 10, the c-axis of the nitride semiconductor 100 is oriented in the vertical direction of the page. More specifically, the c-axis of the nitride semiconductor 100 is oriented in the vertical direction of the page near the cavity facet 160. On the other hand, as shown in (c) and (d) of Figure 10, the electron diffraction pattern of the dielectric film 201 is a pattern rotated 90° from the electron diffraction pattern of the nitride semiconductor 100. Specifically, the c-axis of the dielectric film 201 is oriented in the horizontal direction of the page regardless of the position. In other words, the c-axis of the crystal contained in the dielectric film 201 is perpendicular to the cavity facet 160.

[0110] The term "perpendicular" as used above does not only mean being completely perpendicular, but also includes a manufacturing tolerance. For example, the term "perpendicular" as used above does not only mean that the angle between the two c-axes is 90°, but also includes a tolerance of about ±5% to ±10%.

[0111] The orientation direction of the dielectric film 201 may vary depending on the position.

[0112] The dielectric multilayer films 200 and 300 have the above-described configuration, for example, but are not limited to the above.

[0113] For example, in each dielectric film of the dielectric multilayer films 200, 300, in the dielectric film to which yttrium is added, lanthanum may be added instead of yttrium, or lanthanum may be added together with yttrium.

[0114] The sum of the concentration of yttrium and the concentration of lanthanum in the dielectric film 201 and the dielectric film 202 is not particularly limited, but is, for example, 0.4 atom % or less each.

[0115] Fig. 11 is a graph showing the optical properties of YAlON. Specifically, Fig. 11 is a graph showing the optical absorption coefficient at 405 nm versus the Y content of the AlON film. Fig. 12 is a graph showing the optical properties of YAl2O3. Specifically, Fig. 12 is a graph showing the optical absorption coefficient at 405 nm versus the Y content of the Al2O3 film.

[0116] The addition of Y to the dielectric film terminates grain boundaries and oxygen defects in the dielectric film, reducing the optical absorption coefficient of both Al2O3 and AlON. On the other hand, if the amount of Y added is too large, cluster regions consisting of multiple Y atoms are formed, which act as optical absorption sources, increasing the optical absorption coefficient. These optical absorption characteristics are shown for 405 nm as an example, and the same tendency is observed in the range from 370 nm to 430 nm. In particular, at wavelengths shorter than 405 nm, the optical absorption coefficient is large even without Y addition, and the change in optical absorption characteristics due to Y addition is more pronounced.

[0117] Furthermore, the atomic radius of Y (and La) is relatively large compared to Al. Therefore, when attempting to form a dielectric film with a Y concentration of approximately 1 atom% or more relative to Al, it is difficult to form a stable solid target. Therefore, from the viewpoints of light absorption and manufacturing, the Y concentration is preferably 0.4 atom% or less.

[0118] <Nitride semiconductor light-emitting device> Fig. 13 is a diagram showing the configuration of a light emitting device 400 according to an embodiment. In Fig. 13, a cross section of a package 410 is shown to show the internal configuration.

[0119] The nitride semiconductor light emitting device 10 is used in, for example, a light emitting device 400 that utilizes external resonance.

[0120] The light emitting device 400 includes the nitride semiconductor light emitting element 10 , a package 410 , a submount 420 , a collimator lens unit 430 , a diffraction grating 440 , and a coupler 450 .

[0121] The package 410 is a housing that houses the nitride semiconductor light emitting device 10. The package 410 is a so-called CAN package. The package 410 includes lead pins 411, a stem 412, a window 413, and a cap 414.

[0122] The lead pin 411 is a pin for receiving power supplied to the nitride semiconductor light emitting element 10 from outside the package 410. The lead pin 411 is fixed to the stem 412. The lead pin 411 is made of, for example, a conductive metal material.

[0123] The stem 412 is a base on which the nitride semiconductor light emitting device 10 is placed. In this embodiment, the nitride semiconductor light emitting device 10 is placed on the stem 412 via a submount 420. The stem 412 is made of, for example, a metal material.

[0124] The window 413 is a light-transmitting member that is translucent to the light emitted by the nitride semiconductor light-emitting element 10. The window 413 is formed, for example, from a light-transmitting resin material or a low-reflectivity member coated with a dielectric multilayer film. For example, when the nitride semiconductor light-emitting element 10 emits a short-wavelength laser light, a member made of a transparent material such as glass or quartz and coated with a dielectric multilayer film is used as the window 413 to suppress deterioration.

[0125] The cap 414 is a member provided in contact with the stem 412 so as to cover the nitride semiconductor light-emitting element 10. A through-hole is provided in the cap 414, and light emitted by the nitride semiconductor light-emitting element 10 through the through-hole is emitted to the outside of the package 410. For example, a window 413 is provided so as to cover the through-hole. The nitride semiconductor light-emitting element 10 is hermetically sealed by the stem 412, the window 413, and the cap 414, for example.

[0126] The submount 420 is a substrate on which the nitride semiconductor light emitting device 10 is mounted. The submount 420 is made of, for example, a ceramic material.

[0127] The collimator lens unit 430 is an optical member for collimating the light emitted from the nitride semiconductor light emitting element 10. For example, the collimator lens unit 430 includes a collimator lens 431 that collimates one of the fast axis direction and the slow axis direction of the light (more specifically, laser light) emitted from the nitride semiconductor light emitting element 10, and a collimator lens 432 that collimates the other.

[0128] Diffraction grating 440 is an optical element that disperses light collimated by collimator lens unit 430. Diffraction grating 440 has, for example, a plurality of grooves formed therein, and transmits or reflects the light collimated by collimator lens unit 430 in different directions for each wavelength, and emits the light. In this example, diffraction grating 440 transmits and emits the light collimated by collimator lens unit 430 in different directions for each wavelength. Diffraction grating 440 is, for example, a light-transmitting member such as glass or resin, on whose surface the above-described plurality of grooves are formed.

[0129] The coupler 450 is an output coupler such as a half mirror that transmits a portion of the light emitted by the diffraction grating 440 and reflects the other portion. The light reflected by the coupler 450 passes through the diffraction grating 440 and the collimator lens unit 430 and returns to the nitride semiconductor light-emitting element 10. This causes the light to resonate between the nitride semiconductor light-emitting element 10 and the coupler 450, and the resonated light is emitted from the coupler 450. Specifically, by appropriately arranging the nitride semiconductor light-emitting element 10, the collimator lens unit 430, the diffraction grating 440, and the coupler 450, light of a specific wavelength is resonated and output from the light-emitting device 400.

[0130] In recent years, many applications have been proposed that use external resonance to fix the wavelength of light (e.g., laser light) emitted from nitride semiconductors. For example, in the light source of a Raman spectrometer or photoluminescence device, which are examples of such applications, a light source with a fixed wavelength of light is used because wavelength changes affect the analysis results.

[0131] Furthermore, high-power light-emitting devices require multiple laser beams to be combined, and wavelength combining technology, which combines laser beams fixed at different wavelengths, has attracted attention because it enables high power output while maintaining high beam quality.

[0132] It is generally known that the wavelength of light emitted from a nitride semiconductor changes depending on its operating temperature. Therefore, for example, the wavelength of light emitted by the nitride semiconductor changes depending on the optical output or operating environment of the nitride semiconductor. For this reason, nitride semiconductors are less likely to be used in the above applications where wavelength stability is required.

[0133] Therefore, an external cavity semiconductor laser device has been developed that uses a nitride semiconductor in which the reflectance of the cavity facet (front end facet) of the nitride semiconductor is minimized, a wavelength selection optical element (e.g., diffraction grating 440), and a light emitting optical element called an output coupler (e.g., coupler 450) to form a Fabry-Perot cavity in which only a specific wavelength is amplified.

[0134] 13, light (e.g., laser light) emitted from the nitride semiconductor light-emitting element 10 is collimated by a collimator lens unit 430 to form parallel light, which then enters a diffraction grating 440. The incident light is wavelength-selected by the dispersion effect of the diffraction grating 440, and enters a coupler 450, which serves as the light-emitting surface of a Fabry-Perot cavity arranged in the transmission direction of the desired wavelength. With this configuration, a cavity is formed between the coupler 450 and the cavity surface 160 of the nitride semiconductor 100, and the light is amplified.

[0135] 14 to 16 are graphs showing the reflectance spectra of dielectric multilayer films. Specifically, Fig. 14 is a graph showing the wavelength dependence of reflectance in a dielectric multilayer film 200 formed so as to have a low reflectance for light of 450 nm. Fig. 15 is a graph showing the wavelength dependence of reflectance in a dielectric multilayer film 200 formed so as to have a low reflectance for light of 405 nm. Fig. 16 is a graph showing the wavelength dependence of reflectance in a dielectric multilayer film 200 formed so as to have a low reflectance for light of 375 nm. The reflectance spectra shown in Figs. 14 to 16 are graphs when Al2O3 films are used as the materials for the dielectric films 202 and 204 in the dielectric multilayer film 200.

[0136] 14 to 16, the wavelength dependence of the reflectance when the Al2O3 film (dielectric films 202, 204) is crystallized is shown by a broken line, and the wavelength dependence of the reflectance when the Al2O3 film is amorphous is shown by a solid line.

[0137] 14 to 16, the wavelength dependence of the reflectance when the Al2O3 film is crystallized is different from that when the Al2O3 film is amorphous. As described above, the wavelength dependence of the reflectance differs between crystalline and amorphous, and therefore, when the amorphous state crystallizes, this becomes a cause of fluctuations in the optical characteristics of the nitride semiconductor light-emitting element 10. Furthermore, since the reflectance increases when the amorphous state crystallizes, in the case of an external resonator (e.g., light-emitting device 400), such fluctuations in the optical characteristics result in optical loss, resulting in a decrease in the optical output of the light-emitting device 400.

[0138] In a semiconductor laser device using external resonance such as light emitting device 400, the cavity facets (the faces that generate resonance) are the rear end facet (cavity facet 161) of nitride semiconductor light emitting element 10 and the reflecting facet of coupler 450.

[0139] Therefore, all light reflections occurring at points other than the cavity facets along the optical path where resonance occurs result in light loss (internal loss). Therefore, reflections at the front end facet (cavity facet 160) of nitride semiconductor light-emitting element 10 also result in internal loss. For this reason, the front end facet needs to have an extremely low reflectance.

[0140] Furthermore, if light reflected by a place other than coupler 450 also returns to cavity facet 161 of nitride semiconductor light-emitting element 10, that light may also be amplified by resonance. If the reflectivity of cavity facet 160 of nitride semiconductor light-emitting element 10 becomes high, light is amplified not only by coupler 450 but also by cavity facet 160 (cavity facet of the Fabry-Perot cavity), resulting in the loss of wavelength locking by diffraction grating 440. In other words, it becomes impossible to amplify only light of a specific wavelength. This may also lead to fluctuations in the optical output from light-emitting device 400. For these reasons, the reflectivity of cavity facet 160 of nitride semiconductor light-emitting element 10 must be extremely low, below 1%, and fluctuations must be small. Thus, for example, the reflectivity of dielectric multilayer film 200 may be set to 1% or less by setting the film thickness and other factors according to the wavelength of light emitted by nitride semiconductor 100. That is, for example, the reflectivity of cavity facet 160 on which dielectric multilayer film 200 is stacked may be, for example, 1% or less.

[0141] When a conventional facet protection film not containing Y (e.g., dielectric multilayer film 200A, 2000, etc.) is used, the reflectance of the facet protection film fluctuates while the nitride semiconductor light-emitting element 10 is operating (e.g., while outputting light) due to photo-crystallization of each dielectric film or film peeling between each film.

[0142] 14 to 16, it can be seen that the crystallization of Al2O3 often increases the reflectance at the desired wavelength. Even a slight change in reflectance increases the loss of light due to resonance, leading to a deterioration in the optical characteristics of the light emitting device 400. Furthermore, if film peeling occurs due to stress changes caused by crystallization, the deterioration in the optical characteristics of the light emitting device 400 becomes even more pronounced.

[0143] Therefore, at least one of Y and La (Y in this embodiment) is added to the dielectric films (e.g., dielectric films 202, 302, etc.) made of Al2O3 in the dielectric multilayer films 200, 300. This suppresses photocrystallization of the dielectric films made of Al2O3. Furthermore, the addition of at least one of Y and La (Y in this embodiment) improves adhesion between the dielectric films, thereby suppressing film peeling between the films. This makes it possible to suppress slight variations in reflectance in the dielectric multilayer films 200, 300, and therefore enables stable external resonance in the nitride semiconductor light-emitting device 10. Of course, even when resonance is caused at the cavity facets 160, 161, stable resonance is possible because slight variations in reflectance in the dielectric multilayer films 200, 300 can be suppressed.

[0144] 13, the laser light passes linearly through the diffraction grating 440 and reaches the coupler 450, but this is not limiting. Since the light is bent in accordance with the transmission diffraction angle of the diffraction grating 440, the coupler 440 may be positioned at a position suitable for the diffraction angle of the diffraction grating 440.

[0145] Furthermore, the diffraction grating 440 may reflect and emit the light collimated by the collimator lens unit 430 in different directions for each wavelength.

[0146] FIG. 17 is a diagram showing another example of the configuration of a light emitting device 401 according to an embodiment.

[0147] Light emitting device 401 differs from light emitting device 400 in that light emitting device 401 includes diffraction grating 441 and coupler 460 instead of diffraction grating 440 and coupler 450 .

[0148] Diffraction grating 441 reflects and emits the light collimated by collimator lens unit 430 in different directions for each wavelength. Diffraction grating 441 is, for example, a reflective member such as a metal member with a plurality of grooves formed on its surface.

[0149] Coupler 460 is an output coupler such as a half mirror that transmits part of the light emitted by diffraction grating 441 as a result of reflection and reflects the other part.

[0150] The light emitting device 401 also resonates light between the nitride semiconductor light emitting element 10 and the coupler 460, and the resonated light is emitted from the coupler 460 (that is, the light emitting device 401).

[0151] <Modification> Next, a modified example of the nitride semiconductor light emitting device will be described.

[0152] For example, the dielectric multilayer films 200 and 300 may further include a dielectric film (first optical film) 206 located between the cavity facets 160 and 161 and the dielectric films 201 and 301, respectively.

[0153] Fig. 18 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to Modification 1 of the embodiment, Fig. 19 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to Comparative Example 1.

[0154] The dielectric multilayer film 200C included in the nitride semiconductor light-emitting device according to the first variation of the embodiment has a dielectric film 206 stacked on the cavity facet 160, a dielectric film 201 stacked on the dielectric film 206, a dielectric film 202 stacked on the dielectric film 201, a dielectric film 203 stacked on the dielectric film 202, and a dielectric film 205 stacked on the dielectric film 203.

[0155] Dielectric film 201 may be disposed in contact with cavity facet 160 as shown in FIG. 2, or dielectric film 206 may be disposed in contact with cavity facet 160 as shown in FIG.

[0156] Dielectric film 206 is disposed between cavity facet 160 and dielectric film 201 (i.e., stacked on cavity facet 160), and is a film made of SiN or SiON. In this embodiment, dielectric film 206 is a film made of SiN.

[0157] As shown in FIG. 19, the dielectric multilayer film 200D included in the nitride semiconductor light-emitting device of Comparative Example 1 has a dielectric film 206 stacked on the cavity facet 160, a dielectric film 201A stacked on the dielectric film 206, a dielectric film 202A stacked on the dielectric film 201A, a dielectric film 203A stacked on the dielectric film 202A, and a dielectric film 205 stacked on the dielectric film 203A.

[0158] As described above, the dielectric film 201A is a film made of AlON, the dielectric film 202A is a film made of Al2O3, and the dielectric film 203A is a film made of AlON. In other words, the dielectric films 201, 202, and 203 are different from the dielectric films 201A, 202A, and 203A in that Y is added.

[0159] As shown in FIG. 19, the dielectric film 206 is visible in the dielectric multilayer film 200D. That is, in the structure without Y addition, the SiN film is separated from the AlON film, making it visible. On the other hand, as shown in FIG. 18, the dielectric film 206 is not visible in the dielectric multilayer film 200C. This is thought to be because, in the dielectric multilayer film, an alloy called silicide is formed between the Si contained in the dielectric film 206 and the Y contained in the dielectric film 201. That is, in the structure with Y addition, the SiN film is fused with the YAlON film (more specifically, silicide is formed), making it not visible. Such silicide formation significantly improves the adhesion between the facets (e.g., cavity facets 160) of the nitride semiconductor 100 and the dielectric film (e.g., dielectric film 206).

[0160] Dielectric multilayer film 300 may include a film made of SiN or SiON (that is, a film having the same configuration as dielectric film 206) disposed between cavity facet 161 and dielectric film 301.

[0161] Fig. 20 shows a TEM image of a nitride semiconductor light-emitting device according to Modification 2 of the embodiment. Specifically, (a) of Fig. 20 is a TEM image of the nitride semiconductor light-emitting device according to Modification 2. (b) of Fig. 20 shows an electron beam diffraction pattern at position D. (c) of Fig. 20 shows an electron beam diffraction pattern at position E. Note that Fig. 20 shows an example in which a film is formed by ECR sputtering using an Al target in which 1 wt % of Y is dissolved in Al. The first crystal layer 211 has a thickness of approximately 10 nm.

[0162] 20 , the dielectric film 210 has a c-axis oriented in the vertical direction of the page in the first crystal layer 211 located on the nitride semiconductor 100 side, as in FIG. 19 . That is, the c-axis of the crystal contained in the first crystal layer 211 of the dielectric film 210 is parallel to the cavity facet 160. On the other hand, the dielectric film 210 has a c-axis oriented in the horizontal direction of the page in the second crystal layer 212 located on the dielectric film 202 side. That is, the c-axis of the crystal contained in the first crystal layer 212 of the dielectric film 210 is perpendicular to the cavity facet 160. Thus, for example, the dielectric film 201 is a crystalline film including crystals with a hexagonal crystal structure. The dielectric film 201 includes a first crystal layer 211 whose c-axis is parallel to the cavity facet 160 and a second crystal layer 212 whose c-axis is perpendicular to the cavity facet 160. In this case, for example, the first crystal layer 212 is disposed closer to the cavity facet 160 than the second crystal layer 212 .

[0163] As described above, the first crystal layer 211 has the same orientation as the nitride semiconductor 100 and is an epitaxial film. On the other hand, the second crystal layer 212 has a different orientation from the first crystal layer 211. As shown in (a) of Figure 20, it can be seen that the first crystal layer 211 and the second crystal layer 212 are continuously bonded, and the interface is unclear. This is thought to be because the adhesion-improving effect of Y is greater because the layers are made of the same material but with different orientations.

[0164] Such a configuration may also be employed for dielectric film 301. That is, for example, dielectric film 301 is a crystalline film including crystals with a hexagonal crystal structure. Dielectric film 301 includes a first crystalline layer whose c-axis is parallel to cavity facet 161 and a second crystalline layer whose c-axis is perpendicular to cavity facet 161. In this case, for example, the first crystalline layer is disposed closer to cavity facet 161 than the second crystalline layer.

[0165] Furthermore, for example, the crystals contained in the dielectric film 203 differ from the crystals contained in the dielectric film 201 in at least one of the crystal structure and the crystal orientation.

[0166] FIG. 21 is a diagram showing a TEM image of the nitride semiconductor light emitting device according to the third modification of the embodiment.

[0167] Specifically, (a) of Fig. 21 is a TEM image of the nitride semiconductor light-emitting device according to Modification 3. (b) of Fig. 21 is a diagram showing an electron diffraction pattern at position F. (c) of Fig. 21 is a diagram showing an electron diffraction pattern at position G. (d) of Fig. 21 is a diagram showing an electron diffraction pattern at position H. (e) of Fig. 21 is a diagram showing an electron diffraction pattern of a GaN substrate.

[0168] The dielectric film 206 disposed on the side of the nitride semiconductor 100 close to the cavity facet 160 has the function of suppressing decomposition and oxidation of the facet, and its main purpose is to protect the facet.

[0169] On the other hand, the main purpose of the dielectric films (e.g., dielectric films 201 to 204) formed on the dielectric film 206 is to control the reflectance. Therefore, the crystal structure of the dielectric film provided to control the reflectance is required to be a dense film in which the crystal orientation is appropriately controlled.

[0170] Such dense crystalline films are characterized by strong film stress. When a dielectric film intended to control reflectivity is a multilayer film, the thickness of each dielectric film and the number of films in the multilayer film are set according to the desired reflectivity, and therefore, in a dense crystalline film in which strong stress is generated, film peeling occurs due to thermal shock or the like.

[0171] Therefore, by adding Y and reducing the density of the crystals contained in the dielectric film, it is possible to alleviate stress and prevent film peeling. Specifically, by making the dielectric film a polycrystalline film containing amorphous, it is possible to reduce the film density and alleviate stress.

[0172] The clarity of the electron diffraction pattern and the number of electron diffraction spots also suggest that the dielectric film 210 made of YAlON is a dense crystalline film with controlled crystal orientation.

[0173] On the other hand, the dielectric film 203 made of YAlON was shown to contain crystalline regions as evidenced by the electron diffraction pattern obtained, but the number of diffraction spots was small and the periodicity was lower than that of the dielectric film 201. The electron diffraction pattern obtained suggested multiple orientations, and therefore the dielectric film 203 is considered to be a polycrystalline body containing a mixture of crystalline regions with different orientations.

[0174] The dielectric films 301 and 303 may also have the same configuration as the dielectric film 203. That is, for example, the crystals contained in the dielectric film 303 differ from the crystals contained in the dielectric film 301 in at least one of the crystal structure and the crystal orientation.

[0175] Furthermore, the crystals contained in the dielectric film 303 may differ from the crystals contained in the dielectric film 301 in at least one of the crystal structure and the crystal orientation.

[0176] Furthermore, the optical interference film 310 can be made to have a low reflectance by appropriately selecting the material and film thickness. The dielectric multilayer film 200 may further include a multilayer coating film having such a low reflectance.

[0177] [Manufacturing method] <Nitride semiconductors> The nitride semiconductor 100 is formed by epitaxially growing an N clad layer 111, an N guide layer 112, an N-side guide layer 121, an active layer 122, a P-side guide layer 123, an intermediate layer 124, an electron barrier layer 131, a P clad layer 132, and a contact layer 133 in this order on a main surface (upper surface) of a substrate 102 made of N-type GaN, for example, by metalorganic chemical vapor deposition (MOCVD).

[0178] For example, TMG (trimethylgallium) or TEG (triethylgallium) is used as a Ga source for III group elements. TMA (trimethylaluminum) is used as an Al source. TMI (trimethylindium) is used as an In source. Ammonia (NH3) is used as an N source for V group elements. Silane (SiH4) is used as a Si source containing an N-type dopant. Biscyclopentadienylmagnesium (Cp2Mg) is used as an Mg source containing a P-type dopant.

[0179] Next, a mask film (current blocking layer 141) made of SiO 2 is formed on the contact layer 133 by lithography and etching, covering the region where the ridge portion is to be formed.

[0180] Next, using the formed mask film, dry etching is performed using chlorine (Cl2) as the main component to form a striped ridge portion on the contact layer 133 and the upper part of the P cladding layer 132, with the crystal axis oriented in the <1-100> direction relative to the main surface of the substrate 102.

[0181] Here, the minus sign attached to the index of the crystal axis conveniently represents the inversion of the index following the sign. The width of the ridge portion in the P cladding layer 132 is, for example, 30 μm.

[0182] Next, for example, a method combining vacuum deposition and lift-off is used to deposit a P-side electrode 142 made of Pd and Pt on the contact layer 133, and then a pad electrode 143 is deposited using the same lift-off method as used to form the P-side electrode 142.

[0183] Next, the substrate 102 is thinned (backside polished) to facilitate cleavage of the substrate 102, and then an N-side electrode 101 made of Ti is formed on the backside (lower surface) of the substrate 102 by vacuum deposition, sputtering, or CVD.

[0184] Next, the epitaxial layers (each layer epitaxially grown above) and the substrate 102 are cleaved so that the length of the cavity in the ridge portion is 800 μm or 1200 μm, thereby forming end face mirrors (i.e., cavity faces 160, 161) whose plane orientation of the nitride semiconductor 100 is the (1-100) plane.

[0185] In this way, the nitride semiconductor 100 is manufactured.

[0186] <Dielectric multilayer film> The dielectric multilayer films 200 and 300 can be formed by RF sputtering, magnetron sputtering, ECR (electron cyclotron resonance) sputtering, etc. In this embodiment, the dielectric multilayer films 200 and 300 are formed by ECR sputtering.

[0187] The ECR sputtering method is suitable for forming films on semiconductors because the kinetic energy of the sputtered ions irradiated onto the cavity facets 160 and 161 of the nitride semiconductor 100 is small, which can reduce the density of crystal defects that occur on the exposed surface of the semiconductor due to ion irradiation.

[0188] Dielectric films made of AlON and Al2O3 doped with Y or La (e.g., dielectric films 201-204, 301-303, second coating film 322) can be formed by reactive sputtering using (i) a combination of an AlN target material containing Y or La with nitrogen (N2) gas and oxygen (O2) gas, or (ii) a combination of a metal target material in which Y or La is solid-solved in Al with nitrogen gas.

[0189] In particular, since the sputtering rate increases when a voltage is applied to the target, a solid solution metal target is used in this embodiment. The oxygen and nitrogen compositions in the oxynitride are controlled by adjusting the flow rates of oxygen gas and nitrogen gas introduced into the chamber.

[0190] In this embodiment, an Al metal target material containing 1 wt % Y as a solid solution is used, and the purity of the AlON film can be easily increased by metal refining. When depositing the AlON film, a mixed gas of oxygen and nitrogen is used as the reactive gas.

[0191] In order to control the film formation rate, Ar gas is introduced into the ECR chamber together with oxygen gas and nitrogen gas.

[0192] In this embodiment, the flow rates of argon gas, nitrogen gas, and oxygen gas are set to 30 ml / min, 5.5 ml / min, and 0.3 ml / min, respectively, for forming an AlON film. However, these gas flow rates are merely examples and are not limited to these.

[0193] In this embodiment, the dielectric film 206 made of silicon nitride (SiN) and the dielectric film made of silicon oxide (SiO) (e.g., the dielectric film 205, the first coating film 321) are also formed by the ECR sputtering method using a Si target.

[0194] [Effects, etc.] As described above, nitride semiconductor light-emitting element 10 includes nitride semiconductor 100 having two opposing cavity facets 160, 161, and a dielectric multilayer film including a first dielectric film stacked on at least one of the two cavity facets 160, 161 and a second dielectric film stacked on the first dielectric film. For example, nitride semiconductor light-emitting element 10 includes at least one of dielectric multilayer film 200 stacked on cavity facet 160 and dielectric multilayer film 300 stacked on cavity facet 161. The first dielectric film (dielectric films 201, 301) is made of aluminum oxynitride, and the second dielectric film (dielectric films 202, 302) is made of aluminum oxide. The first dielectric film is a crystalline film, and at least one of yttrium and lanthanum is added to the first dielectric film, and at least one of yttrium and lanthanum is added to the second dielectric film.

[0195] According to this, by adding Y or La, which has a stronger bond energy with oxygen than Al, it is possible to suppress a solid-state reaction (interface solid-state reaction) mediated by oxygen diffusion at the interface between AlON and Al2O3. Therefore, even a multi-layer dielectric film such as the dielectric multilayer films 200 and 300 can be made less susceptible to film peeling, thereby improving the reliability of the nitride semiconductor light-emitting element 10. Furthermore, since a multi-layer dielectric film such as the dielectric multilayer films 200 and 300 can be made, it is easier to control the reflectance. In a conventional structure, when amorphous Al2O3 is formed on a crystalline AlON film, a solid-state reaction mediated by oxygen diffusion occurs between the AlON and Al2O3 due to the difference in stress between the crystalline film and the amorphous film and light absorption by dangling bonds formed at the interface. This easily causes film peeling. Therefore, at least one of Y and La (Y in this embodiment) is added to the dielectric films 201, 202, 301, and 302. For example, when Y is added to both an AlON film and an Al2O3 film, Y acts as an intervening element between these films, holding them together. This makes the films less susceptible to peeling. Furthermore, for example, Y terminates dangling bonds, suppressing solid-state reactions caused by light absorption by dangling bonds. Furthermore, by using an ECR sputtering system and depositing films using an Al-Y (or Al-La) solid target, YAlON and YAl2O3 can be deposited consecutively in the same deposition chamber. In other words, YAlON and YAl2O3 films can be deposited easily. La also has the same effect as Y.

[0196] Furthermore, for example, the dielectric multilayer film has a first optical film made of SiN or SiON arranged between the first dielectric film and at least one of cavity facets 160 and 161. For example, as shown in Fig. 18, dielectric multilayer film 200C has dielectric film 206 arranged between cavity facet 160 and dielectric film 201.

[0197] For example, if crystallized YAlON is directly stacked on the cavity facet 160 of a nitride semiconductor 100 made of GaN, numerous dangling bonds will be generated at the interface between the nitride semiconductor 100 and the YAlON, and these dangling bonds may become a source of light absorption. Furthermore, the difference in stress between the nitride semiconductor 100 and the YAlON may cause film peeling. In the conventional configuration, a film made of SiN and a film made of AlON or Al2O3 that does not contain Y are separated because Si and Al are eutectic compounds, which causes adhesion problems.

[0198] Here, since the first dielectric film of the dielectric multilayer film included in the nitride semiconductor light-emitting device 10 contains Y (or La), even if Si and Al are a eutectic compound, Si and Y (or La) form an alloy called a silicide. Specifically, the Y (or La) contained in the dielectric film 201 is concentrated at the interface with the crystal grains or the dielectric film 206. Due to this concentration, the Si contained in the dielectric film 206 and the Y (or La) contained in the dielectric film 201 form a silicide at the interface. Therefore, the adhesion between the dielectric film 206 and the dielectric film 201 can be improved.

[0199] If oxygen-containing YAlON is directly stacked on cavity facets 160 of nitride semiconductor 100 made of GaN, oxygen may oxidize cavity facets 160 during deposition of the YAlON. Therefore, the first optical film (dielectric film 206) is preferably SiN.

[0200] Also, for example, the first dielectric film (dielectric films 201, 301) has an oxygen concentration of 2 atom % or more and 13.4 atom % or less.

[0201] For example, Y has a higher bond energy with oxygen than Al, and therefore a high chemical ability to capture oxygen, which is effective in suppressing oxidation of cavity facets 160 and 161. On the other hand, Y traps oxygen and oxidizes, which easily causes changes in the refractive index of a dielectric film made of YAlON. Therefore, for example, in the configuration disclosed in Patent Document 4, the change in reflectance of a film made of YAlN due to oxygen capture by Y is large.

[0202] As shown in Figure 9, AlON, the base material of dielectric films 201 and 301, has a stable region where the refractive index varies little with the oxygen composition. On the other hand, for example, AlN, the refractive index decreases with the presence of trace amounts of oxygen. Furthermore, when the oxygen composition of AlON increases, AlON undergoes a phase change and becomes amorphous, causing a sudden decrease in the refractive index.

[0203] Therefore, by setting the oxygen concentration of the first dielectric film (dielectric films 201, 301) to 2 atom % or more and 13.4 atom % or less, it is possible to reduce the change in refractive index caused by oxygen absorption (trapping) in the first dielectric film. Therefore, it is possible to realize a nitride semiconductor light-emitting device 10 whose reflectance is less likely to change with use, that is, a nitride semiconductor light-emitting device 10 with further improved reliability.

[0204] Also, for example, the dielectric multilayer film 200 has a dielectric film 203 laminated on the dielectric film 202, and a dielectric film 204 laminated on the dielectric film 203. The dielectric film 203 is made of aluminum oxynitride, and the dielectric film 204 is made of aluminum oxide. The dielectric film 203 is at least partially crystallized. The dielectric film 203 is doped with at least one of yttrium and lanthanum. The dielectric film 204 is doped with at least one of yttrium and lanthanum.

[0205] YAlON has a higher refractive index than YAl2O3. As a result, dielectric film 203 made of YAlON with a high refractive index and dielectric film 204 made of YAl2O3 with a low refractive index are provided on dielectric film 201 and dielectric film 202. In this way, by stacking multiple films with appropriate thicknesses having different refractive indices, dielectric multilayer film 200 can be controlled to have a desired reflectance. Therefore, as described above, a dielectric multilayer film having a configuration such as dielectric films 201 to 204 can easily control the reflectance to a desired value while making it less likely for the dielectric films to deteriorate and peel off due to such deterioration.

[0206] Furthermore, for example, the dielectric multilayer film 200 includes a second optical film (dielectric film 205) made of silicon oxide laminated on at least one of the dielectric film 201, the dielectric film 202, the dielectric film 203, and the dielectric film 204.

[0207] As a result, as described above, Y (or La) is concentrated in the crystal grains or at the interface, and Si and Y (or La) form silicide, thereby improving the adhesion between dielectric films.

[0208] Furthermore, for example, the dielectric film 206 is located at a position (i.e., the outermost layer) farthest from at least one of the cavity faces (e.g., cavity face 160) among the multiple films (e.g., dielectric films 201 to 205) included in the dielectric multilayer film 200.

[0209] To achieve low reflectance at cavity end facet 160, it is desirable to provide the outermost layer of dielectric multilayer film 200 with a dielectric material whose refractive index is close to that of air. Examples of versatile dielectric materials with low refractive index include silicon oxides such as SiO2. However, SiO2 has an extremely low thermal expansion coefficient, and when it is disposed on other dielectric films, the risk of film peeling due to stress differences increases. In particular, film peeling is likely to occur in conditions where the light-emitting end facet is exposed to high temperatures, such as in laser devices, and this can be a cause of reliability degradation. Therefore, SiO2 is provided as the outermost layer, as in dielectric multilayer film 200. This reduces reflectance by reducing the refractive index difference between air and dielectric multilayer film 200 using dielectric film 206. By maximizing the distance from cavity end facet 160, heat-induced film peeling is suppressed. Furthermore, dielectric film 205 can be stacked with improved adhesion due to the effect of forming a silicide between Si and Y (or La). Therefore, a nitride semiconductor light-emitting element 10 with the desired low reflectance and even higher reliability is achieved.

[0210] Furthermore, for example, the crystals contained in the third dielectric film (e.g., dielectric film 203, 303) differ from the crystals contained in the first dielectric film (e.g., dielectric film 201, 301) in at least one of the crystal structure and the crystal orientation.

[0211] When an amorphous film and a crystalline film are stacked in contact with each other, the difference in stress between these films makes them prone to peeling. Therefore, for example, by reducing the crystallinity of the third dielectric film (i.e., by increasing the amorphous portion or making the crystalline structure slightly more disordered than the most stable structure), the stress can be alleviated (reduced), making peeling less likely to occur.

[0212] Furthermore, for example, the dielectric multilayer film 300 is formed by repeatedly depositing a multilayer coating film 320 at least twice in succession, the multilayer coating film 320 being a combination of a first coating film 321 made of silicon oxide and a second coating film 322 made of aluminum oxynitride laminated on the first coating film 321, and the second coating film 322 is doped with at least one element of yttrium or lanthanum.

[0213] In order to increase the optical output from the nitride semiconductor 100, it is necessary to increase the reflectivity at the cavity facet 161. For example, to increase the optical output from the nitride semiconductor 100, it is desirable to set the reflectivity at the cavity facet 161 to 90% or higher. Such high reflectivity at the cavity facet 161 can be achieved by stacking an optical interference film (optical interference film 310) on the cavity facet 161, which is composed of multiple stacked pairs of high-refractive-index films and low-refractive-index films, known as 1 / 4λ films. In this case, the refractive index difference between the high-refractive-index films and the low-refractive-index films is important. If this refractive index difference is small, a large number of pairs (i.e., the number of dielectric films) is required to achieve high reflectivity. On the other hand, if this refractive index difference is large, a similar effect can be achieved with a smaller number of pairs compared to when the refractive index difference is small. Therefore, a SiO2 film is generally used as the low-refractive-index film. However, SiO2 is a material with an extremely small thermal expansion coefficient. Therefore, when SiO2 is placed on other dielectric films, there is a risk of film peeling due to the stress difference with the other dielectric films. In particular, in laser devices, the chip (e.g., nitride semiconductor 100) can become hot, causing stress-induced film peeling, which can be one of the causes of reliability degradation. Therefore, to further strengthen adhesion and improve reliability, the multilayer coating film 320 of the nitride semiconductor light-emitting device 10 uses a YAlON film as the high-refractive index film (second coating film 322) and SiO2 as the low-refractive index film (first coating film 321). This improves adhesion because silicide is formed between Si and Y at the interface between the silicon oxide (e.g., SiO2) and the YAlON film. Furthermore, for example, SiO2 has a smaller refractive index than YAlON. Therefore, if the optical interference film 310 has multiple multilayer coating films 320 each consisting of a low-refractive index SiO2 film and a high-refractive index YAlON film, the desired reflectance can be achieved by appropriately setting the film thickness of each film. For example, in the dielectric multilayer film 300, the adhesion between the dielectric films (coating films) is improved and high reflectance is achieved.

[0214] For example, such a multilayer coating film may be used for the dielectric multilayer film 200. In this case, by appropriately setting the thickness of each film, similarly to the dielectric multilayer film 300, it is possible to improve the adhesion between the dielectric films (coating films) and achieve low reflectance.

[0215] Furthermore, for example, the reflectance of one of the two cavity faces 160, 161 (cavity face 160 in this embodiment) is 90% or more, and the reflectance of the other of the two cavity faces (cavity face 161 in this embodiment) is 1% or less.

[0216] This makes it possible to suppress the loss of light due to the influence of the reflectance of the cavity faces 160 and 161 .

[0217] Also, for example, nitride semiconductor 100 has a hexagonal crystal structure, at least one of cavity facets 160 and 161 is an m-plane of the hexagonal crystal planes, and first dielectric film includes crystals having a hexagonal crystal structure, and the c-axis of the crystals included in the first dielectric film is perpendicular to at least one of the cavity facets. In this embodiment, cavity facets 160 are m-planes, and dielectric film 201 includes crystals having a hexagonal crystal structure. The c-axis of the crystals included in dielectric film 201 is perpendicular to cavity facets 160, i.e., parallel to the normal to cavity facets 160.

[0218] According to this, for example, cavity facets 160 are m-planes and the c-axis of dielectric film 201 is perpendicular to cavity facets 160, so nitride semiconductor 100 and dielectric film 201 are not in an epitaxial relationship. Therefore, stress caused by the difference in lattice constant between nitride semiconductor 100 and the crystals contained in dielectric film 201 is not applied to cavity facets 160, and deterioration of cavity facets 160 can be suppressed.

[0219] Furthermore, for example, nitride semiconductor 100 has a hexagonal crystal structure, at least one of cavity facets 160, 161 is an m-plane of the hexagonal crystal planes, and first dielectric film is a crystal film including crystals having a hexagonal crystal structure, and first dielectric film includes a first crystal layer whose c-axis is parallel to at least one of the cavity facets and a second crystal layer whose c-axis is perpendicular to at least one of the cavity facets, the first crystal layer being positioned closer to at least one of the cavity facets than the second crystal layer. In this embodiment, dielectric film 210 includes first crystal layer 211 stacked on cavity facet 160 and whose c-axis is parallel to cavity facet 160, and second crystal layer 212 stacked on first crystal layer 211 and whose c-axis is perpendicular to cavity facet 160.

[0220] If a dielectric film that is not epitaxially aligned with the cavity facets 160 is directly stacked on the cavity facets 160, dangling bonds are likely to form on the cavity facets 160. Dangling bonds can act as a source of light absorption, causing the cavity facets 160 to heat up and potentially destroy them. By providing the first crystal layer 211 and the second crystal layer 212, as in the dielectric film 210, the interface corresponding to the break in the crystal plane (i.e., the surface that is no longer epitaxially aligned with the cavity facets 160) can be moved to the inside of the dielectric film 210. This allows Y to concentrate at the interface, thereby terminating dangling bonds. Furthermore, by forming the first crystal layer 211 into a thin film, stress caused by the lattice constant difference on the cavity facets 160 of the nitride semiconductor 100 can be reduced. Increasing the amount of Y, which has a large atomic radius, added is even more effective in further reducing the lattice constant difference.

[0221] Therefore, by making the crystal orientation of first crystal layer 211 closer to cavity facet 160 the same as that of nitride semiconductor 100 (more specifically, cavity facet 160) and making the crystal orientation of second crystal layer 212 different from that of first crystal layer 211, it is possible to terminate dangling bonds of cavity facet 160 and relieve stress inside dielectric film 210, thereby realizing a nitride semiconductor light-emitting element 10 with even higher reliability.

[0222] In order to further reduce the lattice constant difference, it is more effective to increase the amount of Y added, which has a large atomic radius.

[0223] Furthermore, for example, the wavelength of light emitted from the nitride semiconductor 100 is 430 nm or less.

[0224] Fig. 22 is a schematic cross-sectional view showing the configuration of a nitride semiconductor light-emitting device 10B according to Comparative Example 2. Fig. 23 is a view showing a TEM image of the nitride semiconductor light-emitting device 10B according to Comparative Example 2. Fig. 23 shows the nitride semiconductor light-emitting device 10B in which the stripe width of the nitride semiconductor 100 is 30 μm and which was output at 450 nm with CW, Po=5.0 W (@25°C), for 2000 hours.

[0225] As shown in FIG. 22, the nitride semiconductor light emitting device 10B includes a nitride semiconductor 100 and a dielectric multilayer film 200B having dielectric films 201A to 204A and 205.

[0226] As shown in FIG. 23, it can be seen that crystallization has not progressed much in the dielectric film 202A.

[0227] Fig. 24 is a diagram showing another example of a TEM image of the nitride semiconductor light-emitting element 10A according to Comparative Example 3. Fig. 24 is a diagram showing a TEM image of the nitride semiconductor light-emitting element 10A after light output under aging conditions different from those of Fig. 26. Specifically, Fig. 24 shows the nitride semiconductor light-emitting element 10A in which the stripe width of the nitride semiconductor 100 is 30 µm, and which was output at 405 nm with CW, Po = 5.0 W (@25°C), for 1000 hours.

[0228] 24, photo-crystallization of the dielectric film 204A is progressing, and deformation of the dielectric film 204A due to the photo-crystallization is observed. It is also possible to confirm that a solid-phase reaction is progressing near the interface between the dielectric film 201A and the dielectric film 202A.

[0229] 23 and 24 suggest that the rate of photo-crystallization at 450 nm is slower than that at 405 nm. Meanwhile, a white discoloration was observed near the interface between dielectric film 202A and dielectric film 203A. This is thought to be a sign of a solid-state reaction and film peeling.

[0230] It is known that amorphous alumina (Al2O3) that does not contain Y crystallizes when exposed to light (also known as photo-crystallization). It is also known that the speed (rate of crystallization) of photo-crystallization varies depending on the wavelength of light. In particular, the rate of crystallization is slow at 445 nm to 455 nm, which is the wavelength in the blue region used in projectors, lighting fixtures, etc. On the other hand, at wavelengths shorter than this wavelength band, 370 nm to 405 nm, the rate of crystallization is extremely fast when compared, for example, at the same optical density as 445 nm. In particular, the rate of crystallization increases rapidly at wavelengths shorter than 430 nm.

[0231] Although the Al2O3 film is transparent in these wavelength ranges, it is thought that the presence of defects due to oxygen vacancies in the film causes the defects to act as light absorption sources, resulting in light absorption.

[0232] Furthermore, dangling bonds exist at the interface between dielectric films or the interface between the resonator facet and the dielectric film, and light absorption caused by dangling bonds also increases with a shortening of wavelength.

[0233] Here, when Y is added to the Al2O3 film, oxygen defects and dangling bonds are terminated by Y. Furthermore, Y, which has a large atomic radius, has a hindrance effect on atomic displacement within the amorphous phase, suppressing crystallization.

[0234] For these reasons, in a nitride semiconductor light-emitting element 10 including a nitride semiconductor 100 that emits light with a central wavelength of 430 nm or less (for example, the oscillation wavelength of laser light), it is possible to effectively prevent film peeling and achieve high reliability that can stably maintain reflectance.

[0235] Furthermore, for example, the sum of the concentration of yttrium and the concentration of lanthanum in each of the first and second dielectric films is 0.4 atom % or less.

[0236] According to this, by adding at least one of Y and La, both the first dielectric film and the second dielectric film terminate dangling bonds, oxygen defects, etc. at the grain boundaries with at least one of Y and La. As a result, the extinction coefficients of the dielectric multilayer film and the cavity facets are reduced (i.e., the light absorption coefficient is also reduced), which suppresses heat generation at the cavity facets due to light absorption, thereby realizing a nitride semiconductor light emitting element 10 with even higher reliability.

[0237] (Other embodiments) Although the nitride semiconductor light emitting device according to the present disclosure has been described based on the above embodiment, the present disclosure is not limited to the above embodiment.

[0238] For example, in the above embodiment, the structure of nitride semiconductor 100 has been described in detail using Figure 3 etc., but the nitride semiconductor may have any structure that emits light and is not limited to the above embodiment. For example, nitride semiconductor 100 may have a P-type nitride semiconductor layer located below light emitting layer 120 and an N-type nitride semiconductor layer located below light emitting layer 120.

[0239] In addition, the present disclosure also includes forms obtained by applying various modifications to the above embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of each of the above embodiments within the scope of the present disclosure. [Industrial Applicability]

[0240] The nitride semiconductor light-emitting element of the present disclosure can be used as a light source for, for example, industrial lighting, facility lighting, automotive headlamps, industrial laser equipment such as laser processing machines, and image display devices such as laser displays and projectors. [Explanation of symbols]

[0241] 10, 10A, 10B, 1000 Nitride semiconductor light emitting device 100 Nitride Semiconductors 101 N side electrode 102 Circuit Board 110 N-type nitride semiconductor layer 111 N clad layer 112 N guide layer 120 luminescent layer 121 N-side guide layer 122 Active layer 123 P-side guide layer 124 Middle Class 130 P-type nitride semiconductor layer 131 Electron barrier layer 132 P clad layer 133 Contact layer 141 Current Blocking Layer 142 P-side electrode (ohmic electrode) 143 Pad Electrode 160, 161 resonator plane 200, 200A, 200B, 200C, 200D, 2000 Dielectric multilayer film (first dielectric multilayer film) 201, 201A, 301, 210 Dielectric film (first dielectric film) 202, 202A, 302 Dielectric film (second dielectric film) 203, 203A, 303 Dielectric film (third dielectric film) 204, 204A Dielectric film (fourth dielectric film) 205 Dielectric film (second optical film) 206 Dielectric film (first optical film) 211 Crystal Layer (First Crystal Layer) 212 Crystal Layer (Second Crystal Layer) 300 Dielectric multilayer film (second dielectric multilayer film) 310 Optical interference film 320 multilayer coating film 321 First Coating 322 Second Coating 400, 401 Light-emitting device 410 packages 411 Lead pin 412 stem 413 Window 414 Cap 420 Submount 430 Collimator Lens Unit 431, 432 Collimator lenses 440, 441 Diffraction grating 450, 460 coupler 2001, 2002, 2003, 2004, 2005, 2006, 2007 Dielectric Film A, B, C, D, E, F, G, H position

Claims

1. a nitride semiconductor having two cavity faces facing each other; a dielectric multilayer film including a first dielectric film laminated on at least one of the two resonator facets and a second dielectric film laminated on the first dielectric film, the first dielectric film is made of aluminum oxynitride; the second dielectric film is made of aluminum oxide; the first dielectric film is a crystalline film, the first dielectric film is doped with at least one element of yttrium or lanthanum; the second dielectric film is doped with at least one element of yttrium or lanthanum, The dielectric multilayer film is a third dielectric film laminated on the second dielectric film, and a fourth dielectric film laminated on the third dielectric film, the third dielectric film is made of aluminum oxynitride; the fourth dielectric film is made of aluminum oxide, the third dielectric film is at least partially crystallized, the third dielectric film is doped with at least one element of yttrium or lanthanum, the fourth dielectric film is doped with at least one element of yttrium or lanthanum, The crystals contained in the third dielectric film have a different crystal structure from the crystals contained in the first dielectric film. Nitride semiconductor light emitting device.

2. The first dielectric film is a crystalline film in its entirety. The nitride semiconductor light emitting device according to claim 1 .

3. The second dielectric film is amorphous. The nitride semiconductor light-emitting device according to claim 1 or 2.

4. The dielectric multilayer film has a first optical film made of SiN or SiON disposed between the at least one cavity facet and the first dielectric film. The nitride semiconductor light-emitting device according to any one of claims 1 to 3.

5. The first dielectric film has an oxygen concentration of 2 atom % or more and 13.4 atom % or less. The nitride semiconductor light-emitting device according to any one of claims 1 to 4.

6. The dielectric multilayer film includes a second optical film made of silicon oxide laminated on at least one of the first dielectric film, the second dielectric film, the third dielectric film, and the fourth dielectric film. The nitride semiconductor light-emitting device according to any one of claims 1 to 5.

7. The second optical film is located at a position farthest from the at least one cavity facet among the multiple films included in the dielectric multilayer film. The nitride semiconductor light emitting device according to claim 6 .

8. The third dielectric film is a polycrystalline film containing an amorphous phase. The nitride semiconductor light-emitting device according to any one of claims 1 to 7.

9. The dielectric multilayer film is a multilayer coating film, which is a combination of a first coating film made of silicon oxide and a second coating film made of aluminum oxynitride laminated on the first coating film, is repeatedly formed at least twice in succession; The second coating film is doped with at least one element of yttrium or lanthanum. The nitride semiconductor light-emitting device according to any one of claims 1 to 8.

10. the reflectivity of one of the two resonator facets is 90% or more; The reflectance of the other of the two resonator faces is 1% or less. The nitride semiconductor light-emitting device according to any one of claims 1 to 9.

11. the nitride semiconductor has a hexagonal crystal structure, the at least one resonator facet is an m-plane of a hexagonal crystal plane; the first dielectric film contains crystals having a hexagonal crystal structure, The c-axis of the crystal contained in the first dielectric film is perpendicular to the at least one cavity facet. The nitride semiconductor light-emitting device according to any one of claims 1 to 10.

12. the nitride semiconductor has a hexagonal crystal structure, the at least one resonator face is an m-plane of a hexagonal crystal plane, the first dielectric film is a crystalline film containing crystals having a hexagonal crystal structure, The first dielectric film is a first crystal layer whose c-axis is parallel to the at least one cavity facet; a second crystal layer having a c-axis perpendicular to the at least one cavity face; The first crystal layer is disposed closer to the at least one cavity facet than the second crystal layer. The nitride semiconductor light-emitting device according to any one of claims 1 to 11.

13. The wavelength of the light emitted from the nitride semiconductor is 430 nm or less. The nitride semiconductor light-emitting device according to any one of claims 1 to 12.

14. The sum of the concentration of yttrium and the concentration of lanthanum in the first dielectric film and the second dielectric film is 0.05 atom % or less. The nitride semiconductor light-emitting device according to any one of claims 1 to 13.

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