Semiconductor light-emitting element

Abstract

A semiconductor light-emitting element (1) is provided with: a laminated structure (2) that has a first end surface (2F) and a second end surface (2R) that face each other to constitute a resonator, and that includes a nitride semiconductor; and a protective film (3) that is disposed on the first end surface (2F). The protective film (3) includes a first protective film (31a). The first protective film (31a) is an oxide film or an oxynitride film of aluminum to which scandium is added.

Description

Semiconductor light emitting device

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

[0002] Conventionally, semiconductor light-emitting elements such as semiconductor laser elements have been used in various technical fields, and there is a demand for higher optical output. It is generally known that semiconductor light-emitting elements suffer from a destruction phenomenon called catastrophic optical damage (COD) during high optical output operation. Since COD mainly occurs at the light-emitting end face, which is the light-emitting surface of a resonator constituting the semiconductor light-emitting element, efforts have been made to strengthen and stabilize the protective film covering the light-emitting end face.

[0003] For example, in the semiconductor laser device described in Patent Document 1, the stress applied to the active layer is reduced to improve the adhesion of the protective film to the end face.

[0004] Patent No. 5572919

[0005] In the semiconductor laser device described in Patent Document 1, a protective film made of an aluminum oxide film is disposed on the facets that constitute the resonator. In such a semiconductor laser device, the following two reactions occur due to laser light emitted by the semiconductor laser device. The first reaction is a reaction in which oxygen diffuses from the outside into the protective film, oxidizing the facets. The second reaction is a reaction in which the protective film gradually undergoes photocrystallization, causing the protective film to expand or contract. As the facets made of a nitride semiconductor or the like are oxidized by the first reaction, the amount of light absorption (i.e., the amount of heat generated) in the oxidized portions increases, making COD more likely to occur. As such, the semiconductor laser device described in Patent Document 1 does not have sufficient reliability for high-light-output operation.

[0006] The present disclosure is intended to solve such problems, and has an object to provide a highly reliable semiconductor light emitting device.

[0007] In order to solve the above problems, one aspect of the semiconductor light-emitting device according to the present disclosure includes a stacked structure including a nitride semiconductor and having a first end face and a second end face opposing each other to form a resonator, and a protective film disposed on the first end face, the protective film including a first protective film, which is an aluminum oxide film or an aluminum oxynitride film doped with scandium.

[0008] According to the present disclosure, a highly reliable semiconductor light emitting device can be provided.

[0009] 1 is a schematic cross-sectional view showing the configuration of a semiconductor light-emitting device according to a first embodiment; FIG. 2 is a cross-sectional view showing the configuration of a protective film according to the first embodiment; FIG. 3 is a graph showing an overview of the relationship between the amount of photo-crystallization and the amount of oxygen diffusion, and the operating time, of the first protective film according to the first embodiment and the fifth protective film of Comparative Example 1; FIG. 4 is a transmission electron microscope image of the protective film of Comparative Example 1; FIG. 5 is a first transmission electron microscope image of the protective film according to the first embodiment; FIG. 6 is a second transmission electron microscope image of the protective film according to the first embodiment; FIG. 7 is a schematic diagram showing photo-crystallization and oxygen diffusion in the fifth protective film of Comparative Example 1; FIG. 8 is a schematic diagram showing photo-crystallization and oxygen diffusion in the first protective film according to the first embodiment; FIG. 9 is a graph showing the relationship between the light output degradation rate and the aging time of each semiconductor light-emitting device of the first embodiment and Comparative Examples 1 to 3; FIG. 10 is a graph showing the relationship between the rate of change in laser oscillation threshold current (Ith) and the aging time of each semiconductor light-emitting device of the first embodiment and Comparative Examples 1 to 3; FIG. 10 is a schematic diagram showing the shape of the surface of a fifth protective film of Comparative Example 1. FIG. 11 is a schematic diagram showing the shape of the surface of a first protective film according to Embodiment 1. FIG. 12 is a cross-sectional view showing the configuration of a protective film according to Embodiment 2. FIG. 13 is a cross-sectional view showing the configuration of a protective film according to Embodiment 3. FIG. 14 is a cross-sectional view showing the configuration of a protective film according to Embodiment 4. FIG. 15 is a cross-sectional view showing the configuration of a protective film according to Embodiment 5. FIG. 16 is a cross-sectional view showing the configuration of a protective film according to Embodiment 6. FIG. 17 is a cross-sectional view showing the configuration of a protective film according to Embodiment 7. FIG. 18 is a cross-sectional view showing the configuration of a protective film according to Embodiment 8.

[0010] 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.

[0011] 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.

[0012] In this specification, the terms "above" and "below" do not refer to vertically above and below in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. The terms "above" and "below" are used not only when two components are arranged with a gap between them and another component is present between them, but also when two components are arranged in contact with each other.

[0013] First Embodiment A semiconductor light emitting device according to a first embodiment will be described.

[0014] [1-1. Overall Configuration] The overall configuration of the semiconductor light emitting device according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing the configuration of a semiconductor light emitting device 1 according to this embodiment. Fig. 1 shows a cross section parallel to the resonance direction of light in the semiconductor light emitting device 1 and the stacking direction of the stacked structure 2.

[0015] The semiconductor light-emitting element 1 according to the present embodiment is a semiconductor element that emits light. In this embodiment, the semiconductor light-emitting element 1 is an edge-emitting nitride-based semiconductor laser element that includes a nitride semiconductor and emits laser light in the ultraviolet region. As shown in FIG. 1 , the semiconductor light-emitting element 1 according to the present embodiment includes a stacked structure 2 and protective films 3 and 4.

[0016] The laminated structure 2 has a first end face 2F and a second end face 2R that face each other and form a resonator, and includes a nitride semiconductor. The first end face 2F and the second end face 2R are faces located at the ends of the resonance direction (horizontal direction in FIG. 1 ) of the light emitted from the semiconductor light-emitting element 1. The resonance direction is a direction perpendicular to the stacking direction (vertical direction in FIG. 1 ) of the layers included in the laminated structure 2. The first end face 2F is a front end face from which light from the semiconductor light-emitting element 1 is emitted. A protective film 3 is disposed on the first end face 2F. The second end face 2R is a rear end face that reflects light from the semiconductor light-emitting element 1. A protective film 4 is disposed on the second end face 2R. In this embodiment, the laminated structure 2 includes a substrate 21, a first semiconductor layer 22, an active layer 23, and a second semiconductor layer 24.

[0017] The substrate 21 is a plate-like member that serves as a base for the stacked structure 2. In this embodiment, the substrate 21 is an n-type GaN substrate with a (0001) plane. The first end face 2F and the second end face 2R are M-planes.

[0018] The first semiconductor layer 22 is disposed above the substrate 21 and includes a semiconductor layer of a first conductivity type. In the present embodiment, the first conductivity type is n-type, and the first semiconductor layer 22 includes an n-side cladding layer made of an n-type nitride semiconductor. Note that the first semiconductor layer 22 may include an n-type or undoped semiconductor layer other than the n-side cladding layer.

[0019] The active layer 23 is disposed above the first semiconductor layer 22 and is a layer that emits light. In this embodiment, the active layer 23 is a quantum well active layer that includes a plurality of barrier layers and one or more well layers. The active layer 23 may include a first optical guide layer having an average refractive index higher than that of the first semiconductor layer 22, a second optical guide layer having an average refractive index higher than that of the second semiconductor layer 24, and the like.

[0020] The second semiconductor layer 24 is disposed above the active layer 23 and includes a semiconductor layer of a second conductivity type. The second conductivity type is a conductivity type different from the first conductivity type. In the present embodiment, the second conductivity type is p-type, and the second semiconductor layer 24 includes a p-side cladding layer made of a p-type nitride semiconductor. Note that the second semiconductor layer 24 may include a p-type or undoped semiconductor layer other than the p-side cladding layer.

[0021] Electrodes (not shown) may be arranged on the stacked structure 2. That is, electrodes may be arranged on the lower surface of the substrate 21 (i.e., one of the two main surfaces of the substrate 21, the main surface on the back side of the main surface on which the first semiconductor layer 22 is stacked) and the upper surface of the second semiconductor layer 24 (i.e., one of the two main surfaces of the second semiconductor layer 24, the main surface on the back side of the main surface in contact with the active layer 23).

[0022] The protective film 3 is disposed on the first end facet 2F. The protective film 3 will be described below with reference to FIG. 2. FIG. 2 is a cross-sectional view showing the configuration of the protective film 3 according to this embodiment. FIG. 2 also shows the stacked structure 2. FIG. 2 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element 1 and the stacking direction of the stacked structure 2.

[0023] The protective film 3 includes at least one of a first protective film and a second protective film. As shown in FIG. 2 , the protective film 3 includes first protective films 31 a and 31 b. The protective film 3 also includes second protective films 32 a and 32 b. In this embodiment, the protective film 3 further includes a third protective film 33 and a fourth protective film 34. As shown in FIG. 2 , each layer included in the protective film 3 is stacked on the first end face 2F.

[0024] Each of the first protective films 31a and 31b is an oxide film or an oxynitride film of aluminum (Al) to which scandium (Sc) is added. In this embodiment, each of the first protective films 31a and 31b is an Al oxide film or an oxynitride film to which scandium (Sc) is added. ２ O ３ (Al ２ O ３The first protective films 31a and 31b are Al:O:Sc films. The concentration of scandium added to the first protective films 31a and 31b is greater than 0 atomic % (hereinafter referred to as at%) and less than 10 at%. The concentration of scandium added to the first protective films 31a and 31b may be less than 7 at% or less, less than 5 at% or less, less than 3 at% or less, or less than 1 at%. The concentration of scandium added to the first protective films 31a and 31b may be 0.1 at% or more. In this embodiment, the concentration of scandium added to the first protective films 31a and 31b is 0.2 at%. In this embodiment, the first protective films 31a and 31b are fabricated based on a design value of the composition ratio (at%) of Al:O:Sc = 39.8:60:0.2. The composition ratio of the first protective film 31a may be different from the composition ratio of the first protective film 31b. The first protective film 31a has a thickness of 12 nm, and the first protective film 31b has a thickness of 152 nm. Each of the first protective films 31a and 31b is amorphous or amorphous containing a crystalline phase, but may also be crystalline.

[0025] 2, the second protective film 32a is disposed between the first end face 2F and the first protective film 31a. The second protective film 32b is disposed between the first end face 2F and the first protective film 31b. The second protective film 32a contacts the first protective film 31a, and the second protective film 32b contacts the first protective film 31b. In other words, the protective film 3 includes a plurality of stacked films 38a, 38b, each of which includes a first protective film and a second protective film in contact with the first protective film. Specifically, the stacked film 38a includes the first protective film 31a and the second protective film 32a in contact with the first protective film 31a, and the stacked film 38b includes the first protective film 31b and the second protective film 32b in contact with the first protective film 31b. In this embodiment, the protective film 3 includes two laminated films 38a and 38b, but may include a single laminated film, or may include three or more laminated films.

[0026] Each of the second protective films 32a, 32b is a crystalline film made of aluminum nitride or oxynitride. In this embodiment, the second protective films 32a, 32b are AlON (AlON:Sc) films doped with scandium. The concentration of scandium added to the second protective films 32a, 32b is greater than 0 at% and less than or equal to 10 at%. The concentration of scandium added to the second protective films 32a, 32b may be less than or equal to 7 at%, less than or equal to 5 at%, less than or equal to 3 at%, or less than or equal to 1 at%. The concentration of scandium added to the second protective films 32a, 32b may also be greater than or equal to 0.1 at%. In this embodiment, the concentration of scandium added to the second protective films 32a, 32b is 0.3 at%. In this embodiment, the second protective films 32a and 32b are fabricated based on a design value of the composition ratio (at %) of Al:O:N:Sc = 49.7:12:38:0.3. The composition ratio of the second protective film 32a may be different from the composition ratio of the second protective film 32b. The thickness of the second protective film 32a is 20 nm, and the thickness of the second protective film 32b is 10 nm. The crystal structure of the second protective films 32a and 32b is a polycrystalline structure composed of at least one of a hexagonal crystal and a cubic crystal. Here, the cubic crystal refers to a cubic crystal in the narrow sense, excluding crystals with a perovskite structure. In this embodiment, the second protective films 32a and 32b are hexagonal crystals with an m-axis orientation relative to the first end face 2F. Although the second protective films 32a and 32b are hexagonal crystals with an m-axis orientation in this embodiment, the orientation characteristics of the second protective films 32a and 32b are not limited thereto. For example, the orientation characteristics of the second protective films 32a and 32b may be c-axis orientation, mc mixed orientation (that is, orientation characteristics in which m-axis orientation and c-axis orientation are mixed), or oblique orientation.

[0027] The third protective film 33 contacts the first end facet 2F. The third protective film 33 is disposed between the first end facet 2F and the second protective film 32a. The third protective film 33 is a silicon nitride film or silicon oxynitride film. In this embodiment, the third protective film 33 is a SiN film with a thickness of 0.5 nm. In this embodiment, the third protective film 33 is fabricated based on a design value of the composition ratio (at %) of Si:N = 42.9:57.1. The third protective film 33 is amorphous.

[0028] The fourth protective film 34 is a silicon oxide film. The fourth protective film 34 is disposed at a position farther from the first end face 2F than the first protective films 31a and 31b. In other words, the first protective films 31a and 31b are disposed between the first end face 2F and the fourth protective film 34. The first protective film 31b is in contact with the fourth protective film 34. In this embodiment, the fourth protective film 34 is a 54 nm-thick SiO ２ In this embodiment, the fourth protective film 34 is fabricated based on a design value of composition ratio (at %) of Si:O=33.3:66.7. The fourth protective film 34 is amorphous.

[0029] The protective film 4 is disposed on the second end facet 2R. Like the protective film 3, the protective film 4 may include a first protective film that is an aluminum oxide film or oxynitride film doped with scandium. Alternatively, the protective film 4 may include a protective film having a composition similar to at least one of the second protective films 32a, 32b, the third protective film 33, and the fourth protective film 34. The reflectance at the second end facet 2R on which the protective film 4 is disposed is greater than the reflectance at the first end facet 2F on which the protective film 3 is disposed.

[0030] [1-2. Effects] The effects of the semiconductor light emitting device 1 according to this embodiment will be described in comparison with a semiconductor light emitting device of Comparative Example 1. The semiconductor light emitting device of Comparative Example 1 has a structure in which the first protective films 31a and 31b of the protective film 3 are replaced with Al SiO 2 SiO 2 not doped with scandium. ２ O ３ and in that sixth protective films 932a, 932b made of AlON without scandium added are used instead of the second protective films 32a, 32b, but are the same in other respects.

[0031] The photocrystallization amount and oxygen diffusion amount of the first protective films 31a and 31b according to the present embodiment and the fifth protective films 931a and 931b according to Comparative Example 1 will be described with reference to FIG. 3 . FIG. 3 is a graph showing an overview of the relationship between the photocrystallization amount and oxygen diffusion amount of the first protective films 31a and 31b according to the present embodiment and the fifth protective films 931a and 931b according to Comparative Example 1 and the drive time. Here, drive time refers to the time during which current is supplied to each of the semiconductor light emitting device 1 according to the present embodiment and the semiconductor light emitting device according to the comparative example to emit light. Graph (a) of FIG. 3 shows the relationship between the photocrystallization amount and drive time, while graph (b) of FIG. 3 shows the relationship between the oxygen diffusion amount and drive time. In both the first protective films 31a and 31b according to the present embodiment and the fifth protective films 931a and 931b according to Comparative Example 1, photocrystallization and oxygen diffusion occur as the drive time elapses. Photocrystallization is a phenomenon in which amorphous portions are crystallized by light emitted by each semiconductor light emitting device. Oxygen diffusion is a phenomenon in which oxygen present outside each protective film is absorbed into the protective film and diffuses therein. ２ O ３ The oxygen atoms bonded to the aluminum atoms in the do not diffuse.

[0032] As shown in graph (a) of FIG. 3 , photocrystallization progresses more rapidly in the first protective films 31a and 31b according to this embodiment than in the fifth protective films 931a and 931b according to Comparative Example 1. This photocrystallization will be explained using FIGS. 4 to 6 . FIG. 4 is a transmission electron microscope (TEM) image of the protective film according to Comparative Example 1. FIGS. 5 and 6 are first and second TEM images, respectively, of the protective film 3 according to this embodiment. FIG. 5 is an enlarged TEM image of the rectangular frame V shown in FIG. 6 . In FIG. 6 , the boundary between the inner region R1 and the outer region R2 of the first protective films 31a and 31b is indicated by a white dashed line. FIGS. 4 to 6 show the state of each protective film after an aging test was performed on each semiconductor light-emitting device. In the aging test, each semiconductor light-emitting device was exposed to 1.4 W of continuous wave (CW) laser light for 1,000 hours. The black portions of the fifth protective films 931a and 931b shown in FIG. 4 and the first protective films 31a and 31b shown in FIG. 5 are photocrystallized regions CR. As shown in FIG. 4, the region of the fifth protective film 931a near the interface with the sixth protective film 932a and a portion of the fifth protective film 931b are photocrystallized. As shown in FIGS. 5 and 6, a wide region indicated by an internal region R1 between the first protective film 31a and the first protective film 31b is photocrystallized. As such, the first protective films 31a and 31b according to this embodiment exhibit a greater amount of photocrystallization after the aging test than the fifth protective films 931a and 931b of Comparative Example 1. As shown in FIG. 6, this photocrystallization occurs primarily in the internal region R1, which includes the region (optical path) through which light emitted from each semiconductor light-emitting element propagates and its vicinity. In other words, the inner region R1 of the first protective films 31a and 31b, which includes the optical path, is photo-crystallized, while the outer region R2 located outside the inner region R1 is not photo-crystallized and remains amorphous. It is estimated that the refractive index of the inner region R1 of the first protective films 31a and 31b increases as a result of this photo-crystallization. Note that no photo-crystallization was observed in any of the protective films other than the first protective films 31a and 31b after the aging test.

[0033] 6, the photo-crystallized region CR of the first protective film 31a is wider than that of the first protective film 31b. In other words, the photo-crystallized region of the first protective film 31a extends to a region farther from the optical path than that of the first protective film 31b.

[0034] Photo-crystallization and oxygen diffusion are both phenomena that occur when the protective films are irradiated with light, and are mutually competing phenomena. Therefore, in the first protective films 31 a and 31 b, which are photo-crystallized more quickly, oxygen diffusion is suppressed more than in the fifth protective films 931 a and 931 b, as shown in graph (b) of FIG.

[0035] The mechanism by which rapid photo-crystallization occurs in the first protective films 31a, 31b according to the present embodiment as described above has not yet been clarified, but it is speculated that the addition of scandium may create atomic-level spaces (vacancies) for atoms to move, which are necessary for photo-crystallization to occur.

[0036] Furthermore, the photo-crystallized regions of the first protective films 31a and 31b have the effect of suppressing oxygen diffusion. This effect will be described with reference to FIGS. 7 and 8 . FIGS. 7 and 8 are schematic diagrams showing photo-crystallization and oxygen diffusion in the fifth protective film 931a of Comparative Example 1 and the first protective film 31a according to the present embodiment, respectively. The schematic diagrams (a) and (b) show the respective protective films immediately after deposition, the schematic diagrams (b) and (c) show the respective photo-crystallization and oxygen diffusion states of the respective protective films after a relatively short time (e.g., 500 hours) has elapsed since the start of operation of the respective semiconductor light-emitting elements.

[0037] As shown in the schematic diagrams (a) of Figures 7 and 8, the fifth protective film 931a and the first protective film 31a are not irradiated with light immediately after deposition, and therefore photocrystallization and oxygen diffusion do not occur. In the semiconductor light-emitting device of Comparative Example 1, as shown in the schematic diagram (b) of Figure 7, oxygen diffusion is dominant among the oxygen diffusion and photocrystallization in the fifth protective film 931a after operation starts. Therefore, it takes a long time (e.g., 5,000 hours) for the fifth protective film 931a to be photocrystallized after operation starts. Although the photocrystallized region of the fifth protective film 931a has the effect of suppressing oxygen diffusion, photocrystallization takes a long time. Therefore, by the time the entire optical path of the fifth protective film 931a is photocrystallized, oxygen diffused in the fifth protective film 931a reaches the stacked structure 2. As a result, the nitride semiconductor of the stacked structure 2 is oxidized, increasing light absorption in the stacked structure 2, making the semiconductor light-emitting device of Comparative Example 1 more susceptible to COD.

[0038] 7(c), the entire optical path of the fifth protective film 931a is photocrystallized, which can prevent oxygen diffused in the fifth protective film 931a from reaching the stacked structure 2. In other words, it is possible to prevent acceleration of characteristic degradation due to further oxygen diffusion.

[0039] On the other hand, in the first protective film 31a according to this embodiment, after the start of operation, photo-crystallization becomes dominant among oxygen diffusion and photo-crystallization in the first protective film 31a, and the first protective film 31a is photo-crystallized quickly (for example, after 100 hours). Therefore, as shown in the schematic diagram (b) of FIG. 8 , the first protective film 31a is photo-crystallized, so oxygen diffusion is suppressed in the photo-crystallized region, and oxygen can be prevented from reaching the stacked structure 2. Therefore, in this embodiment, oxidation of the nitride semiconductor of the stacked structure 2 can be suppressed, and light absorption in the stacked structure 2 can be suppressed. Therefore, the occurrence of COD in the semiconductor light-emitting element 1 can be suppressed.

[0040] Furthermore, as shown in the schematic diagram (c) of Figure 8, even if the device is driven continuously for a long period of time, oxygen diffused in the first protective film 31a can be prevented from reaching the stacked structure 2, thereby preventing the acceleration of characteristic degradation.

[0041] As described above, the semiconductor light emitting device 1 according to this embodiment is provided with first protective films 31a, 31b, which are aluminum oxide films doped with scandium, and thus can have higher reliability than the semiconductor light emitting device of Comparative Example 1. Note that, in this embodiment, aluminum oxide films doped with scandium are used as first protective films 31a, 31b, but similar effects can be obtained by using aluminum oxynitride films doped with scandium.

[0042] 9 to 11, the experimental results of the semiconductor light emitting element 1 according to the present embodiment and the semiconductor light emitting elements of Comparative Examples 1 to 3 will be described. The semiconductor light emitting elements of Comparative Examples 2 and 3 have AlN doped with yttrium (Y) instead of the first protective films 31a and 31b of the protective film 3 of the semiconductor light emitting element 1 according to the present embodiment. ２ O ３ (Al ２ O ３ The semiconductor light emitting device according to Comparative Example 2 and Comparative Example 3 differs from the semiconductor light emitting device 1 according to the present embodiment in that a seventh protective film made of AlON (AlON:Y) is used and that an eighth protective film made of AlON doped with yttrium (AlON:Y) is used instead of the second protective films 32a and 32b, but is the same in other respects. The yttrium concentrations in the seventh protective films of the semiconductor light emitting devices according to Comparative Example 2 and Comparative Example 3 are 1.0% and 8.0%, respectively. The yttrium concentrations in the eighth protective films of the semiconductor light emitting devices according to Comparative Example 2 and Comparative Example 3 are 1.0% and 8.0%, respectively.

[0043] FIG. 9 is a graph showing the relationship between the optical output degradation rate and aging time for each of the semiconductor light-emitting devices of the present embodiment and Comparative Examples 1 to 3. The optical output degradation rate [%] is defined as (P1-P0) x 100 / P0, where P0 is the optical output before the aging test (i.e., aging time 0) and P1 is the optical output after the aging test. FIG. 10 is a graph showing the relationship between the laser oscillation threshold current (Ith) change rate and aging time for each of the semiconductor light-emitting devices of the present embodiment and Comparative Examples 1 to 3. The Ith change rate [%] is defined as (Ith1-Ith0) x 100 / Ith0, where Ith0 is the laser oscillation threshold current before the aging test and Ith1 is the laser oscillation threshold current after the aging test. FIG. 11 is a graph showing the relationship between the slope efficiency (Se) change rate and aging time for each of the semiconductor light-emitting devices of the present embodiment and Comparative Examples 1 to 3. The Se change rate [%] is defined as (Se1-Se0) x 100 / Se0, where Se0 is the slope efficiency before the aging test and Se1 is the slope efficiency after the aging test.

[0044] As shown in Fig. 9, in the semiconductor light-emitting element 1 according to the present embodiment, the rate of light output degradation after 300 hours of aging is greater than that of each of the semiconductor light-emitting elements of Comparative Examples 1 to 3, but the rate of light output degradation after 1000 hours of aging is smaller than that of each of the semiconductor light-emitting elements of Comparative Examples 1 to 3. Also, as shown in Fig. 10, in the semiconductor light-emitting element 1 according to the present embodiment, the laser oscillation threshold hardly changes even after 1000 hours of aging. Also, as shown in Fig. 11, in the semiconductor light-emitting element 1 according to the present embodiment, the rate of Se change after 300 hours of aging is greater than that of each of the semiconductor light-emitting elements of Comparative Examples 2 and 3, but the rate of light output degradation after 1000 hours of aging is smaller than that of each of the semiconductor light-emitting elements of Comparative Examples 1 to 3.

[0045] As described above, in this embodiment, a highly reliable semiconductor light emitting element 1 capable of suppressing deterioration due to aging can be realized.

[0046] Furthermore, the semiconductor light emitting device 1 according to this embodiment can improve the FFP (Far Field Pattern) of the emitted light (laser light). This effect will be described with reference to FIGS. 12 and 13 in comparison with Comparative Example 1. FIGS. 12 and 13 are schematic diagrams showing the shapes of the surfaces SF of the fifth protective film 931a of Comparative Example 1 and the first protective film 31a according to this embodiment, respectively. FIGS. 12 and 13 also show the stacked structure 2, the third protective film 33, and the second protective film 32a. The dashed lines shown in FIGS. 12 and 13 indicate the outer edges of the optical paths.

[0047] 12 , in the fifth protective film 931a of Comparative Example 1, photo-crystallization proceeds relatively slowly (see the photo-crystallized region CR shown in FIG. 12 ), and therefore, the change in film thickness along the optical path due to photo-crystallization becomes non-uniform. In other words, the flatness of the surface SF of the fifth protective film 931a decreases. Therefore, in the semiconductor light-emitting device of Comparative Example 1, a disturbance in the FFP occurs due to the change in film thickness of the fifth protective film 931a.

[0048] On the other hand, in the first protective film 31a according to this embodiment, as shown in FIG. 13, photo-crystallization (see photo-crystallized region CR shown in FIG. 13) progresses quickly, so the film thickness of the first protective film 31a within the optical path becomes substantially uniform. In other words, it is possible to suppress a decrease in the flatness of the surface SF of the first protective film 31a within the optical path. Therefore, in the semiconductor light-emitting device 1 according to this embodiment, it is possible to suppress disturbances in the FFP. In other words, in the semiconductor light-emitting device 1 according to this embodiment, it is possible to stabilize the FFP.

[0049] The first protective films 31a and 31b according to this embodiment may be amorphous or amorphous containing a crystalline phase.

[0050] This reduces the energy applied to the stacked structure 2 during film formation compared to when crystalline protective films are formed as the first protective films 31a and 31b. Therefore, damage to the stacked structure 2 during film formation of the first protective films 31a and 31b can be suppressed. At the same time, damage to the second protective film 32a and the third protective film 33 can also be suppressed. This further improves the reliability of the semiconductor light emitting element 1.

[0051] The concentration of scandium added to the first protective films 31a and 31b according to this embodiment may be 10 at % or less.

[0052] This can further promote photo-crystallization in the first protective films 31a and 31b.

[0053] The protective film 3 may include a second protective film 32a disposed between the first end face 2F and the first protective film 31a, and the second protective film 32a may be a crystalline film made of a nitride or oxynitride of aluminum doped with scandium. The protective film 3 according to this embodiment may include a second protective film 32b disposed between the first end face 2F and the first protective film 31b, and the second protective film 32b may be a crystalline film made of a nitride or oxynitride of aluminum doped with scandium.

[0054] By disposing each second protective film, which is such a crystalline film, between the first end face 2F and each first protective film, each second protective film may be able to promote photo-crystallization of each first protective film or may be able to trap oxygen. This further suppresses oxygen diffusion in each first protective film, thereby further suppressing oxidation of the stacked structure 2. This further improves the reliability of the semiconductor light-emitting element 1.

[0055] Furthermore, by arranging the second protective films 32a and 32b on the first end surface 2F side of the first protective films 31a and 31b, respectively, the first protective films 31a and 31b can suppress oxygen diffusion to the second protective films 32a and 32b, thereby suppressing oxidation of the second protective films 32a and 32b.

[0056] The crystalline structure of the second protective films 32a and 32b may be a polycrystalline structure made of at least one of a hexagonal crystal structure and a cubic crystal structure.

[0057] The second protective films 32a and 32b may be hexagonal crystals oriented along the m-axis with respect to the first end face 2F.

[0058] In this case, scandium, which has a larger atomic radius and ionic radius than aluminum and gallium, is added to the hexagonal second protective films 32a, 32b, so that the lattice constants of the second protective films 32a, 32b approach the lattice constant of the stacked structure 2. This may reduce dangling bonds at the interface between the stacked structure 2 and the protective film 3, and reduce crystal defects. Reducing dangling bonds in this way reduces crystal defects near the interface between the stacked structure 2 and the protective film 3, and also reduces light absorption. This further improves the reliability of the semiconductor light-emitting element 1.

[0059] The protective film 3 may include a plurality of laminated films 38a, 38b. Each of the laminated films 38a, 38b includes a first protective film 31a and a second protective film 32a in contact with the first protective film 31a. The laminated film 38b includes a first protective film 31b and a second protective film 32b in contact with the first protective film 31b.

[0060] In this way, the protective film 3 includes a first protective film with a low refractive index and a second protective film with a high refractive index that are alternately arranged, so that the reflectance of the protective film 3 can be easily controlled.

[0061] The protective film 3 includes a third protective film 33 in contact with the first end facet 2F, and the third protective film 33 may be a silicon nitride film or a silicon oxynitride film.

[0062] By including such a third protective film 33 in the protective film 3, there is a possibility that dangling bonds at the interface between the stacked structure 2 and the protective film 3 can be terminated by the third protective film 33. This can improve adhesion between the stacked structure 2 and the protective film (second protective film 32a in this embodiment) adjacent to the stacked structure 2 via the third protective film 33. Furthermore, it is possible to reduce crystal defects near the interface between the stacked structure 2 and the protective film 3, and to reduce light absorption. Therefore, it is possible to further improve the reliability of the semiconductor light emitting element 1.

[0063] The third protective film 33 may be amorphous.

[0064] This can prevent damage to the stacked structure 2 when the third protective film 33 is formed.

[0065] The protective film 3 may include a fourth protective film 34 that is a silicon oxide film, and the first protective films 31a and 31b may be disposed between the first end facet 2F and the fourth protective film 34.

[0066] In this way, the protective film 3 includes the fourth protective film 34 whose refractive index is smaller than that of the first protective films 31a and 31b, so that the reflectance of the protective film 3 can be easily controlled.

[0067] The first protective film 31 b may be in contact with the fourth protective film 34 .

[0068] In this way, contact between the first protective film 31b containing scandium and the fourth protective film 34, which is a silicon oxide film, may result in the formation of silicide (ScSi) at the interface between these films. This can improve the adhesion between the first protective film 31b and the fourth protective film 34. As a result, the reliability of the semiconductor light emitting device 1 can be improved.

[0069] The fourth protective film 34 may be amorphous.

[0070] This makes it possible to suppress damage to the stacked structure 2 when the fourth protective film 34 is formed.

[0071] (Embodiment 2) A protective film according to embodiment 2 will be described. The protective film according to this embodiment differs from the protective film 3 according to embodiment 1 in that it does not include a second protective film, a third protective film, and a fourth protective film. The protective film according to this embodiment will be described below with reference to FIG. 14, focusing on the differences from the protective film 3 according to embodiment 1. FIG. 14 is a cross-sectional view showing the configuration of the protective film according to this embodiment. FIG. 14 also shows the stacked structure 2. FIG. 14 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element and the stacking direction of the stacked structure 2.

[0072] The protective film according to this embodiment is a first protective film 31a, as shown in Fig. 14. In other words, the protective film according to this embodiment includes only the first protective film 31a.

[0073] The first protective film 31a has the same configuration as the first protective film 31a according to Embodiment 1. The first protective film 31a is in contact with the first end face 2F of the multilayer structure 2.

[0074] The first protective film 31a according to this embodiment also has the same effects as the first protective films of the protective film 3 according to the first embodiment.

[0075] Furthermore, the protective film according to this embodiment is made up of only the first protective film 31a, and therefore can be manufactured more easily than the protective film 3 according to the first embodiment.

[0076] (Embodiment 3) A protective film according to embodiment 3 will be described. The protective film according to this embodiment differs from the protective film 3 according to embodiment 1 mainly in the configuration of the second protective film and in that it does not include a third protective film and a fourth protective film. The protective film according to this embodiment will be described below with reference to FIG. 15, focusing on the differences from the protective film 3 according to embodiment 1. FIG. 15 is a cross-sectional view showing the configuration of the protective film 103 according to this embodiment. FIG. 15 also shows the stacked structure 2. FIG. 15 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element and the stacking direction of the stacked structure 2.

[0077] 15 , the protective film 103 according to this embodiment includes a plurality of stacked films 138a, 138b, and 138c. The stacked film 138a includes a first protective film 31a and a second protective film 132a disposed between the first end face 2F and the first protective film 31a and in contact with the first protective film 31a. The stacked film 138b includes a first protective film 31b and a second protective film 132b disposed between the first end face 2F and the first protective film 31b and in contact with the first protective film 31b. The stacked film 138c includes a first protective film 31c and a second protective film 132c disposed between the first end face 2F and the first protective film 31c and in contact with the first protective film 31c.

[0078] The first protective films 31a and 31b have the same configuration as the first protective films 31a and 31b according to the first embodiment. The first protective film 31c is an aluminum oxide film or oxynitride film doped with scandium. The concentration of scandium added to the first protective film 31c is 10 at % or less. The first protective film 31c is amorphous or amorphous containing a crystalline phase, but may also be crystalline.

[0079] The second protective films 132a, 132b, and 132c are crystalline films made of aluminum nitride or oxynitride, similar to the second protective films 32a and 32b according to embodiment 1. The crystalline structure of the second protective films 132a, 132b, and 132c is a polycrystalline structure made of at least one of a hexagonal crystal and a cubic crystal. The second protective films 132a, 132b, and 132c are hexagonal crystals oriented along the m-axis with respect to the first end facet 2F. The second protective films 132a, 132b, and 132c according to this embodiment are undoped nitrides or oxynitrides that are not doped with scandium or the like.

[0080] The first and second protective films included in the protective film 103 according to this embodiment also have the same effects as the first and second protective films of the protective film 3 according to the first embodiment.

[0081] Furthermore, the protective film 103 according to this embodiment includes three stacked films 138a, 138b, and 138c, which makes it easier to control the reflectance of the protective film 103. Although the protective film 103 includes three stacked films 138a, 138b, and 138c in this embodiment, it may include four or more stacked films.

[0082] Furthermore, since the protective film 103 according to this embodiment is composed only of the first protective films 31a, 31b, and 31c and the second protective films 132a, 132b, and 132c, it can be manufactured more easily than the protective film 3 according to the first embodiment.

[0083] (Fourth Embodiment) A protective film according to a fourth embodiment will be described. The protective film according to this embodiment differs from the protective film 103 according to the third embodiment in the configuration of the second protective film. The protective film according to this embodiment will be described below with reference to FIG. 16, focusing on the differences from the protective film 103 according to the third embodiment. FIG. 16 is a cross-sectional view showing the configuration of the protective film 203 according to this embodiment. FIG. 16 also shows the stacked structure 2. FIG. 16 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element and the stacking direction of the stacked structure 2.

[0084] 16 , the protective film 203 according to the present embodiment includes a plurality of stacked films 38a, 38b, and 38c. The stacked films 38a and 38b have the same configuration as the stacked films 38a and 38b according to the first embodiment. The stacked film 38c includes a first protective film 31c and a second protective film 32c that is disposed between the first end facet 2F and the first protective film 31c and that is in contact with the first protective film 31c. The first protective film 31c according to the present embodiment has the same configuration as the first protective film 31c according to the third embodiment.

[0085] The second protective films 32a and 32b have the same configuration as the second protective films 32a and 32b according to embodiment 1. The second protective film 32c is a crystalline film made of aluminum nitride or oxynitride, similar to the second protective films 32a and 32b according to embodiment 1. In this embodiment, the second protective film 32c is a nitride or oxynitride to which 10 at % or less of scandium is added.

[0086] The protective film 203 including the second protective films 32a, 32b, and 32c also has the same effects as the protective film 103 according to the third embodiment.

[0087] (Embodiment 5) A protective film according to embodiment 5 will be described. The protective film according to this embodiment differs from the protective film 3 according to embodiment 1 in that it is composed only of a first protective film and a third protective film. The protective film according to this embodiment will be described below with reference to FIG. 17, focusing on the differences from the protective film 3 according to embodiment 1. FIG. 17 is a cross-sectional view showing the configuration of the protective film 303 according to this embodiment. FIG. 17 also shows the stacked structure 2. FIG. 17 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element and the stacking direction of the stacked structure 2.

[0088] As shown in FIG. 17, the protective film 303 according to this embodiment includes a first protective film 31 a and a third protective film 33 .

[0089] The first protective film 31a has the same configuration as the first protective film 31a according to the first embodiment.

[0090] The third protective film 33 has the same configuration as the third protective film 33 according to Embodiment 1. In this embodiment, the third protective film 33 is in contact with the first protective film 31a.

[0091] The protective film 303 according to this embodiment also provides the same effects as the first protective film 31a and the third protective film 33 according to the first embodiment.

[0092] Furthermore, the protective film 303 according to this embodiment is made up of only two layers, the first protective film 31a and the third protective film 33, and therefore can be manufactured more easily than the protective film 3 according to the first embodiment.

[0093] Sixth Embodiment A protective film according to a sixth embodiment will be described. The protective film according to this embodiment differs from the protective film 203 according to the fourth embodiment in that it includes a third protective film. The protective film according to this embodiment will be described below with reference to FIG. 18, focusing on the differences from the protective film 203 according to the fourth embodiment. FIG. 18 is a cross-sectional view showing the configuration of a protective film 403 according to this embodiment. FIG. 18 also shows the stacked structure 2. FIG. 18 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element and the stacking direction of the stacked structure 2.

[0094] As shown in FIG. 18, the protective film 403 according to this embodiment includes stacked films 38 a , 38 b , and 38 c and a third protective film 33 .

[0095] The third protective film 33 has the same configuration as the third protective film 33 according to the first embodiment.

[0096] The protective film 403 according to this embodiment also provides the same effects as the protective film 203 according to the fourth embodiment.

[0097] Furthermore, the protective film 403 according to this embodiment includes the third protective film 33, and thus has the same effect as the third protective film 33 in the protective film 3 according to the first embodiment.

[0098] Seventh Embodiment A protective film according to a seventh embodiment will be described. The protective film according to this embodiment differs from the protective film 3 according to the first embodiment in that it is composed only of a first protective film and a fourth protective film. The protective film according to this embodiment will be described below with reference to FIG. 19 , focusing on the differences from the protective film 3 according to the first embodiment. FIG. 19 is a cross-sectional view showing the configuration of a protective film 503 according to this embodiment. FIG. 19 also shows a stacked structure 2. FIG. 19 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element and the stacking direction of the stacked structure 2.

[0099] As shown in FIG. 19, the protective film 503 according to this embodiment includes a first protective film 31a and a fourth protective film 34.

[0100] The first protective film 31a has the same configuration as the first protective film 31a according to Embodiment 1. In this embodiment, the first protective film 31a contacts the first end facet 2F.

[0101] The fourth protective film 34 has the same configuration as the fourth protective film 34 according to the embodiment 1. The fourth protective film 34 is in contact with the first protective film 31a.

[0102] The protective film 503 according to this embodiment also exhibits the same effects as the first protective film 31a and the fourth protective film 34 according to the first embodiment.

[0103] Furthermore, the protective film 503 according to this embodiment is made up of only two layers, the first protective film 31a and the fourth protective film 34, and therefore can be manufactured more easily than the protective film 3 according to the first embodiment.

[0104] Eighth Embodiment A protective film according to an eighth embodiment will be described. The protective film according to this embodiment differs from the protective film 3 according to the first embodiment in that the protective film according to this embodiment is composed only of a first protective film, a third protective film, and a fourth protective film. The protective film according to this embodiment will be described below with reference to FIG. 20, focusing on the differences from the protective film 3 according to the first embodiment. FIG. 20 is a cross-sectional view showing the configuration of a protective film 603 according to this embodiment. FIG. 20 also shows a stacked structure 2. FIG. 20 shows a cross section parallel to the resonance direction of light from the semiconductor light emitting element and the stacking direction of the stacked structure 2.

[0105] As shown in FIG. 20, the protective film 603 according to this embodiment includes a first protective film 31 a, a third protective film 33, and a fourth protective film 34.

[0106] The first protective film 31a has the same configuration as the first protective film 31a according to Embodiment 1. In this embodiment, the first protective film 31a is in contact with the third protective film 33 and the fourth protective film .

[0107] The third protective film 33 has the same configuration as the third protective film 33 according to Embodiment 1. The third protective film 33 contacts the first end facet 2F and the first protective film 31a.

[0108] The fourth protective film 34 has the same configuration as the fourth protective film 34 according to the embodiment 1. The fourth protective film 34 is in contact with the first protective film 31a.

[0109] The protective film 603 according to this embodiment also exhibits the same effects as the first protective film 31a, the third protective film 33, and the fourth protective film 34 according to the first embodiment.

[0110] Furthermore, since the protective film 503 according to this embodiment is composed of only three layers, namely, the first protective film 31a, the third protective film 33, and the fourth protective film 34, it can be manufactured more easily than the protective film 3 according to the first embodiment.

[0111] (Modifications, etc.) Although the semiconductor light emitting device according to the present disclosure has been described above based on the respective embodiments, the present disclosure is not limited to the above-described respective embodiments.

[0112] For example, the configuration of the stacked structure 2 according to the present disclosure is not limited to the configuration examples shown in the above-described embodiments. The stacked structure 2 may be any stacked structure including a nitride semiconductor, having a first end face 2F and a second end face 2R that face each other and form a resonator. Furthermore, the light emitted by the stacked structure 2 does not have to be light in the ultraviolet range.

[0113] In addition, although the above-described embodiments have been described with reference to examples in which the semiconductor light-emitting element is a semiconductor laser element, the semiconductor light-emitting element is not limited to a semiconductor laser element. For example, the semiconductor light-emitting element may be a superluminescent diode.

[0114] Furthermore, although the protective film of the semiconductor light-emitting element according to each of the above embodiments includes a first protective film, it may include only a second protective film without the first protective film. That is, the semiconductor light-emitting element according to the present disclosure has a first end facet and a second end facet that face each other and form a resonator, and includes a stacked structure including a nitride semiconductor and a protective film disposed on the first end facet. The protective film may include a second protective film, and the first protective film may be a crystalline film made of an aluminum oxide film or oxynitride film doped with scandium. In such a semiconductor light-emitting element, the second protective film, which is a crystalline film, may be able to trap oxygen. This may suppress oxidation of the stacked structure, thereby improving the reliability of the semiconductor light-emitting element.

[0115] In addition, in each of the above embodiments, the protective film is disposed on both the first end face 2F and the second end face 2R, but it is sufficient that the protective film is disposed on at least one of the first end face 2F and the second end face 2R. In each of the embodiments, each protective film disposed on the first end face 2F may also be disposed on the second end face 2R.

[0116] This disclosure also includes forms obtained by applying various modifications to the above-mentioned embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the above-mentioned embodiments within the scope of the present disclosure.

[0117] The semiconductor light-emitting element according to the present disclosure is particularly useful as an externally resonated semiconductor light-emitting element that requires control of the reflectance of the end face, such as a high-power semiconductor light source such as a light source for laser processing, a high-power light source such as a light source for LDI (Laser Direct Imaging), or a light source for DDL (Direct Diode Laser).

[0118] REFERENCE SIGNS LIST 1 semiconductor light emitting element 2 laminated structure 2F first end face 2R second end face 3, 4, 103, 203, 303, 403, 503, 603 protective film 21 substrate 22 first semiconductor layer 23 active layer 24 second semiconductor layer 31a, 31b, 31c first protective film 32a, 32b, 32c, 132a, 132b, 132c second protective film 33 third protective film 34 fourth protective film 38a, 38b, 38c, 138a, 138b, 138c laminated film 931a, 931b fifth protective film 932a, 932b sixth protective film CR photocrystallized region R1 internal region R2 external region SF surface

Claims

1. A laminated structure containing a nitride semiconductor, having a first end face and a second end face that face each other and constitute a resonator, The system comprises a protective film disposed on the first end face, The protective film includes a first protective film, The first protective film is an aluminum oxide film with scandium added. The first protective film is amorphous. Semiconductor light-emitting element.

2. The concentration of scandium added to the first protective film is 10 at% or less. The semiconductor light-emitting element according to claim 1.

3. The protective film includes a second protective film disposed between the first end face and the first protective film. The second protective film is a crystalline film made of aluminum nitride or oxynitride with scandium added. The semiconductor light-emitting element according to claim 1 or 2.

4. The concentration of scandium added to the second protective film is 10 at% or less. The semiconductor light-emitting element according to claim 3.

5. The crystal structure of the second protective film is a polycrystalline structure consisting of at least one of hexagonal and cubic crystals. The semiconductor light-emitting element according to claim 3.

6. The second protective film is hexagonal with m-axis orientation relative to the first end face. The semiconductor light-emitting element according to claim 3.

7. The protective film includes a plurality of laminated films, Each of the plurality of laminated films includes the first protective film and the second protective film in contact with the first protective film. The semiconductor light-emitting element according to claim 3.

8. The protective film includes a third protective film that is in contact with the first end surface. The third protective film is a silicon nitride film or oxynitride film. A semiconductor light-emitting element according to any one of claims 1 or 2.

9. The third protective film is amorphous. The semiconductor light-emitting element according to claim 8.

10. The protective film includes a fourth protective film which is a silicon oxide film. The first protective film is positioned between the first end face and the fourth protective film. A semiconductor light-emitting element according to any one of claims 1 or 2.

11. The first protective film is in contact with the fourth protective film. The semiconductor light-emitting element according to claim 10.

12. The fourth protective film is amorphous. The semiconductor light-emitting element according to claim 10.

13. The protective film has a photocrystallized region, The photocrystallized region includes at least a portion of the region through which the light emitted by the semiconductor light-emitting element propagates. The dimension of the photocrystallized region in the first protective film in a direction perpendicular to the direction of light propagation takes a minimum value between the two interfaces of the first protective film. The semiconductor light-emitting element according to claim 1 or 2.

14. The protective film has an inner protective film disposed between the first end face and the second protective film, The inner protective film is an aluminum oxide or oxynitride film with scandium added. The protective film has a photocrystallized region that includes at least a portion of the region through which light emitted by the semiconductor light-emitting element propagates. The dimension of the photocrystallization region in the inner protective film in the direction perpendicular to the direction of light propagation is greater than the dimension of the photocrystallization region in the first protective film in the direction perpendicular to the direction of light propagation. The semiconductor light-emitting element according to claim 3.