Semiconductor light emitting device and method for manufacturing the same

Abstract

This semiconductor element (1) comprises a substrate (10), an n-type clad layer (12) disposed on the substrate (10), an active layer (14) disposed on the n-type clad layer (12), and a p-type clad layer (17) disposed on the active layer (14), wherein: the active layer (14) has a well layer (14d), an n-side first barrier layer (14a) disposed on the n-type clad layer (12) side of the well layer (14d), and a p-side barrier layer (14f) disposed on the p-type clad layer (17) of the well layer (14d); the p-side barrier layer (14f) contains In; the In composition ratio of the n-side first barrier layer (14a) is lower than the In composition ratio of the p-side barrier layer (14f); and the bandgap energy of the n-side first barrier layer (14a) is smaller than the bandgap energy of the p-side barrier layer (14f).

Description

[Technical field]

[0001] The present disclosure relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device including an active layer having a quantum well structure. [Background technology]

[0002] Conventionally, laser light has been used for processing purposes, and a high-output and high-efficiency laser light source is required. Semiconductor light-emitting elements such as semiconductor laser elements are used as such laser light sources. Among processing applications, particularly welding processing applications, there is a demand for laser light sources with even higher output.

[0003] An example of a technique for increasing the output of a semiconductor light-emitting device is described in Patent Document 1. Patent Document 1 describes a technique for reducing the energy difference ΔEv between the first quantum level of heavy holes in a well layer and the energy level at the top of the valence band of a barrier layer in an active layer having a quantum well structure, and for increasing the energy difference ΔEc between the first quantum level of electrons in the well layer and the energy level at the bottom of the conduction band of the barrier layer. In the semiconductor light-emitting device described in Patent Document 1, the energy difference ΔEv is reduced to facilitate the movement of holes, thereby increasing the probability of recombination between holes and electrons, while the energy difference ΔEc is increased to suppress the overflow (i.e., leakage) of electrons from the well layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-256659 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the semiconductor light emitting device described in Patent Document 1, the energy difference ΔEc is large, so that the operating voltage required to inject electrons into the well layer increases, and as a result, the self-heating of the semiconductor light emitting device increases, and the thermal saturation level decreases.

[0006] The present disclosure is devised to solve such problems, and has an object to provide a semiconductor light emitting device and the like that can suppress the overflow of electrons from the well layer while suppressing the operating voltage. [Means for solving the problem]

[0007] In order to solve the above problems, one aspect of a semiconductor light-emitting device according to the present disclosure includes a substrate, an n-type cladding layer disposed above the substrate, an active layer disposed above the n-type cladding layer, and a p-type cladding layer disposed above the active layer, the active layer having a well layer, an n-side first barrier layer disposed on the n-type cladding layer side of the well layer, and a p-side barrier layer disposed on the p-type cladding layer side of the well layer, the p-side barrier layer containing In, an In composition ratio of the n-side first barrier layer being lower than an In composition ratio of the p-side barrier layer, and a band gap energy of the n-side first barrier layer being smaller than a band gap energy of the p-side barrier layer.

[0008] In this way, the In composition ratio of the n-side first barrier layer is made smaller than that of the p-side barrier layer, and the band gap of the n-side first barrier layer is made smaller than that of the p-side barrier layer. This makes it possible to make the energy difference ΔEc in the conduction band potential energy between the p-side barrier layer and the n-side first barrier layer larger than the energy difference ΔEv in the valence band potential energy between the p-side barrier layer and the n-side first barrier layer. Therefore, it is possible to suppress the overflow of electrons from the well layer while suppressing an increase in the voltage required for the electrical conduction of holes (i.e., an increase in the operating voltage of the semiconductor light emitting device).

[0009] In one embodiment of the semiconductor light emitting device according to the present disclosure, the composition of the n-side first barrier layer is Al ybn1Ga 1-xbn1-ybn1 In xbn1 It is represented by As, and the composition of the p-side barrier layer is Al ybp1 Ga 1-xbp1-ybp1 In xbp1 It is represented by As, and the relationships 0≦ybn1≦1, 0≦xbn1<1, 0<ybp1<1, 0<xbp1<1, and xbn1<xbp1 may hold.

[0010] By using the n-side first barrier layer and the p-side barrier layer having such compositions, the In composition ratio of the n-side first barrier layer can be made smaller than the In composition ratio of the p-side barrier layer, and the bandgap of the n-side first barrier layer can be made smaller than the bandgap of the p-side barrier layer.

[0011] Also, in one aspect of the semiconductor light-emitting device according to the present disclosure, the relationship ybn1<ybp1 may further hold.

[0012] As a result, since the energy difference ΔEc between the conduction band potential energies of the p-side barrier layer and the n-side first barrier layer increases, the overflow of electrons from the well layer can be further suppressed.

[0013] Also, in one aspect of the semiconductor light-emitting device according to the present disclosure, further 0.2≦ybn1≦0.4 ybp1≦xbp1+0.975ybn1+0.069, ybp1≧0.4xbp1+0.975ybn1+0.029, and xbp1≦0.15 The relationships may hold.

[0014] In this way, by setting the Al composition ratio ybn1 of the n-side first barrier layer to be 0.2 or more and 0.4 or less, it is possible to suppress a significant decrease in the optical confinement coefficient in the well layer and to reduce the loss of the waveguide.

[0015] In addition, for the Al composition ratio ybp1 of the p-side barrier layer, since the above relationship holds, the energy difference ΔEv2 in the valence band potential energy between the n-side first barrier layer and the p-side barrier layer can be suppressed to 30 meV or less, while the energy difference ΔEc2 in the conduction band potential energy between the n-side first barrier layer and the p-side barrier layer can be increased to 25 meV or more. Therefore, by suppressing the energy difference ΔEv2, the increase in the operating voltage can be suppressed, and by increasing the energy difference ΔEc2, the overflow of electrons can be suppressed.

[0016] Furthermore, by setting the Al composition ratio xbp1 of the p-side barrier layer to 0.15 or less, the lattice mismatch between the GaAs substrate and the p-side barrier layer can be suppressed to a maximum of 1.2%.

[0017] In one aspect of the semiconductor light emitting device according to the present disclosure, a p-side intermediate layer is further provided between the well layer and the p-side barrier layer, and the composition of the p-side intermediate layer is Al ykp1 Ga 1-ykp1 It is represented by As, ybp1≦xbp1+0.975ykp1+0.069, ybp1≧0.4xbp1+0.975ykp1+0.029, and 0.2≦ykp1≦0.4 The following relationship may be satisfied.

[0018] When the above relationship is satisfied for the Al composition ratio ybp1 of the p-side barrier layer, the energy difference ΔEc2 in the conduction band potential energy between the p-side barrier layer and the p-side intermediate layer is 25 meV or more, and the energy difference ΔEv2 in the valence band potential energy is 30 meV or less. This makes it possible to suppress the inhibition of the injection of holes into the well layer, thereby suppressing an increase in the operating voltage. In addition, it is possible to suppress the overflow of electrons from the well layer.

[0019] Furthermore, by setting the Al composition ratio of the p-side intermediate layer to be greater than or equal to 0.2 and less than or equal to 0.4, the light distribution in the vertical direction can be controlled with even greater precision, thereby enabling the optical confinement factor to be increased while reducing loss in the waveguide.

[0020] In addition, by disposing a p-side intermediate layer made of an AlGaAs layer that is nearly lattice-matched to the GaAs substrate between the well layer and the p-side barrier layer, the region in which compressive strain is formed near the active layer can be dispersed, thereby suppressing the deterioration of crystallinity due to the concentration of compressive strain.

[0021] Furthermore, the energy difference ΔEv in the valence band potential energy between the well layer and the p-side intermediate layer can be reduced, so that the formation of high-level light holes can be suppressed, thereby suppressing the decrease in the polarization ratio.

[0022] In one embodiment of the semiconductor light emitting device according to the present disclosure, an n-side second barrier layer is further provided between the n-side first barrier layer and the well layer, and the composition of the n-side second barrier layer is Al ybn2 Ga 1-xbn2-ybn2 In xbn2 It is represented by As, ybn2 ≥ xbn2 + ybn1, ybn2≦0.4xbn2+0.975ybn1+0.061, xbn2≦0.15, and 0.2≦ybn1≦0.35 The following relationship may be satisfied.

[0023] When the above relationship is satisfied for the Al composition ratio ybn2 of the n-side second barrier layer, the energy difference ΔEc2 in the conduction band potential energy between the n-side first barrier layer and the n-side second barrier layer is 50 meV or less, and the energy difference ΔEv2 in the valence band potential energy is 30 meV or more. This makes it possible to suppress the inhibition of the injection of electrons into the well layer, thereby suppressing an increase in the operating voltage. In addition, it is possible to suppress the overflow of holes from the well layer.

[0024] In addition, by lowering the Al composition ratio of the n-side first barrier layer to 0.2 or more and 0.35 or less, the refractive index of the n-side first barrier layer can be increased, which makes it easier to shift the light distribution in the vertical direction toward the n-type semiconductor layer side, thereby facilitating the reduction of loss in the waveguide.

[0025] In one embodiment of the semiconductor light emitting device according to the present disclosure, an n-side third barrier layer is further provided between the well layer and the n-side second barrier layer, and the composition of the n-side third barrier layer is Al ybn3 Ga 1-ybn3 It is represented by As, ybn2 ≥ xbn2 + ybn3, ybn2≦0.4xbn2+0.975ybn3+0.061, and 0.2≦ybn3≦0.35 The following relationship may be satisfied.

[0026] Regarding the Al composition ratio ybn2 of the n-side second barrier layer, when the above relationship holds, the energy difference ΔEc2 of the conduction band potential energy between the n-side second barrier layer and the n-side third barrier layer is 50 meV or less. In addition, by setting the Al composition ratio of the n-side third barrier layer to 0.35 or less, the band gap energy in the n-side third barrier layer can be reduced. Therefore, it is possible to suppress the prevention of the injection of electrons into the well layer, and therefore the increase in the operating voltage can be suppressed.

[0027] In addition, when the above relationship is satisfied for the Al composition ratio ybn2 of the n-side second barrier layer, the energy difference ΔEv2 in the valence band potential energy between the n-side second barrier layer and the n-side third barrier layer is 0 meV or more, thereby suppressing the overflow of holes from the well layer.

[0028] In addition, by lowering the Al composition ratio of the n-side third barrier layer to 0.2 or more and 0.35 or less, the refractive index of the n-side third barrier layer can be increased, which makes it easier to shift the light distribution in the vertical direction toward the n-type semiconductor layer side, thereby facilitating the reduction of loss in the waveguide.

[0029] In addition, the semiconductor light emitting device according to one embodiment of the present disclosure may further include a p-side guide layer disposed between the p-side barrier layer and the p-type cladding layer, the p-side guide layer having a refractive index greater than that of the p-type cladding layer.

[0030] In this way, by providing a p-side guide layer having a refractive index larger than that of the p-type cladding layer on the p-side barrier layer, the light distribution in the vertical direction can be controlled with high precision, and the light distribution can be prevented from being too biased toward the n-type semiconductor layer side. Therefore, the light confinement coefficient in the vertical direction to the well layer can be prevented from decreasing, and the operating carrier density in the well layer can be prevented from increasing. In other words, the temperature characteristics of the semiconductor light emitting device can be prevented from deteriorating. Furthermore, if the p-side guide layer is undoped, the increase in free carrier loss due to impurity doping can be prevented, so that the loss of the waveguide can be reduced. As a result, a semiconductor laser device with excellent temperature characteristics and high slope efficiency can be realized.

[0031] In one embodiment of the semiconductor light emitting device according to the present disclosure, the p-side guide layer has a composition of Al ygp1 Ga 1-ygp1 It is represented by As, ybp1≦xbp1+0.975ygp1+0.069, ybp1≧0.4xbp1+0.975ygp1+0.029, and 0.2≦ygp1≦0.4 The following relationship may be satisfied.

[0032] The p-side guide layer having such a composition is nearly lattice-matched to the GaAs substrate. This allows the thickness of the p-side barrier layer having compressive lattice mismatch to be kept below the critical thickness. This prevents the crystallinity of the p-side barrier layer from deteriorating.

[0033] Furthermore, when the well layer is a quaternary semiconductor material film containing Al, the compressive strain in the active layer increases. For this reason, a p-side guide layer that is nearly lattice-matched to the GaAs substrate is placed above the p-side barrier layer to suppress the accumulation of compressive strain near the active layer. In this case, the potential energy between the ground levels of the heavy holes and the light holes increases, reducing the probability of recombination between the light holes and electrons. Therefore, the TM polarization component caused by the recombination between the light holes and electrons can be reduced, improving the polarization ratio.

[0034] By satisfying the above relationship, while suppressing the energy difference ΔEv2 of the valence band potential energy between the p-side barrier layer and the p-side guide layer to 30 meV or less, the energy difference ΔEc2 of the conduction band potential energy can be increased to 25 meV or more. Therefore, it is possible to suppress the overflow of electrons from the well layer while suppressing an increase in the operating voltage.

[0035] In addition, by setting the Al composition ratio ygp1 of the p-side guide layer to 0.2 or more and 0.4 or less, the light distribution in the vertical direction can be controlled with higher precision, and it is possible to suppress a significant decrease in the light confinement factor and reduce the loss of the waveguide.

[0036] In addition, in one aspect of the semiconductor light-emitting device according to the present disclosure, the p-side guide layer may be represented by (Al ygp2 Ga 1-ygp2 ) 0.5 In 0.5 P.

[0037] This makes it easier for holes or impurities such as Zn and Mg to diffuse in the p-side guide layer. Therefore, by diffusing holes or impurities into the semiconductor light-emitting device, the time required for forming the end face window structure can be reduced. In addition, since the concentration of the impurity used when diffusing the impurity can be reduced, light absorption by the impurity can be reduced. Therefore, a decrease in the light emission efficiency of the semiconductor light-emitting device can be suppressed.

[0038] In addition, in one aspect of the semiconductor light-emitting device according to the present disclosure, the composition of the n-type cladding layer is represented by Al yn1 Ga 1-yn1 As, the composition of the p-type cladding layer is represented by Al yp1 Ga 1-yp1 As, and a relationship of 0 < yn1 < yp1 < 1 may be satisfied.

[0039] Thus, since the Al composition ratio of the n-type clad layer is lower than that of the p-type clad layer, the refractive index of the n-type clad layer becomes larger than that of the p-type clad layer. Along with this, the light distribution in the vertical direction is biased toward the n-type clad layer side. As described above, since the free carrier loss that light receives from the waveguide of the semiconductor light-emitting device becomes larger in the p-type semiconductor layer having a higher doping concentration than the n-type semiconductor layer, it is possible to reduce the waveguide loss by making the light distribution in the vertical direction closer to the n-type semiconductor layer.

[0040] Since the light distribution is biased toward the n-type clad layer side, the light confinement coefficient in the vertical direction to the well layer, which is the light-emitting layer, decreases. Therefore, as described above, electrons easily overflow from the well layer to the p-side barrier layer. However, in the semiconductor light-emitting device according to the present disclosure, since the energy difference ΔEc between the conduction band potential energies of the p-side barrier layer and the n-side first barrier layer is large, overflow of electrons can be suppressed. Therefore, it is possible to realize a semiconductor light-emitting device with a low operating current that can improve the temperature characteristics and has a high slope efficiency while suppressing an increase in the operating voltage as compared with a conventional semiconductor light-emitting device.

[0041] Also, in one aspect of the semiconductor light-emitting device according to the present disclosure, the composition of the n-type clad layer is represented by (Al yn2 Ga 1-yn2 ) 0.5 In 0.5 P, the composition of the p-type clad layer is represented by (Al yp2 Ga 1-yp2 ) 0.5 In 0.5 P, and a relationship of 0 < yn2 < yp2 < 1 may hold.

[0042] By providing an n-type clad layer and a p-type clad layer having such a composition, holes or impurities such as Zn and Mg are likely to diffuse in the n-type clad layer and the p-type clad layer. Therefore, by diffusing holes or impurities into the semiconductor light-emitting device, the time required for formation can be reduced when forming the end face window structure. In addition, since the concentration of the impurity used when diffusing the impurity can be reduced, light absorption by the impurity can be reduced. Therefore, a decrease in the light emission efficiency of the semiconductor light-emitting device can be suppressed.

[0043] Further, by establishing the relationship of 0 < yn2 < yp2 < 1, the refractive index of the p-type clad layer can be reduced compared to the refractive index of the n-type clad layer. Therefore, the intensity distribution of the laser light can be biased toward the n-type clad layer side. That is, since the laser light propagating through the p-type clad layer can be reduced, the free carrier loss caused by the impurities in the p-type clad layer can be reduced. As a result, the loss of the waveguide can be reduced.

[0044] Further, in one aspect of the semiconductor light-emitting device according to the present disclosure, the composition of the well layer is Al yw Ga 1-xw-yw In xw represented by As, and the relationships of 0 ≦ yw < 1 and 0 < xw < 1 may hold.

[0045] Thus, when the composition of the well layer is Al yw Ga 1-xw-yw In xw As, by adjusting the Al composition ratio, Ga composition ratio, and In composition ratio of the well layer, the magnitude of the strain of the well layer and the energy differences between the conduction band and valence band of the well layer and each barrier layer can be adjusted. Therefore, it becomes possible to adjust the oscillation wavelength of the semiconductor light-emitting device and control the overflow of electrons from the well layer.

[0046] Further, in one aspect of the semiconductor light-emitting device according to the present disclosure, furthermore, the relationship of 0 < yw < 1 may hold.

[0047] In this way, when the well layer contains Al, the number of light holes formed in the valence band of the well layer can be reduced when the well layer has compressive strain. Here, the proportion of TM mode light is greater in light generated by recombination of light holes (LH) and electrons than in light generated by recombination of heavy holes (HH) and electrons. Therefore, by reducing the number of light holes formed in the valence band of the well layer, the probability of recombination of light holes and electrons can be reduced, and the polarization ratio of output light from the semiconductor light emitting element (the ratio of the intensity of TE mode light to the intensity of TM mode light) can be increased.

[0048] In addition, in one aspect of the semiconductor light emitting device according to the present disclosure, the substrate may be a GaAs substrate.

[0049] In this way, by using a GaAs substrate as the substrate, when an AlGaInAs-based quaternary semiconductor material is used as the barrier layer and well layer, it is possible to generate compressive strain in the well layer. When the well layer has compressive strain, the number of light holes formed in the valence band of the well layer can be reduced by adjusting the composition of the well layer. Therefore, the recombination probability of light holes and electrons can be reduced, and the polarization ratio of the output light from the semiconductor light emitting element can be increased.

[0050] In one embodiment of the semiconductor light emitting device according to the present disclosure, the band gap energy of the n-type cladding layer may be smaller than the band gap energy of the p-type cladding layer.

[0051] As a result, the refractive index of the n-type cladding layer becomes higher than that of the p-type cladding layer. Therefore, the light distribution in the direction perpendicular to the main surface of the substrate is biased toward the n-type cladding layer. Here, in the n-type semiconductor layer, the doping concentration of n-type impurities is set to 1×10 16 cm -3 That's it, 1×10 18 cm -3 The resistance value can be suppressed by setting the doping concentration of p-type impurities in the p-type semiconductor layer to the following range: 18 cm -3If the resistance is not set to 1.0 or more, the resistance value cannot be suppressed. Therefore, the free carrier loss that light receives from the waveguide of the semiconductor light emitting device is larger in the p-type semiconductor layer, which has a higher doping concentration than the n-type semiconductor layer. Therefore, by biasing the light distribution toward the n-type cladding layer as in the semiconductor light emitting device according to the present disclosure, the waveguide loss can be reduced.

[0052] The light distribution is biased toward the n-type cladding layer side, and the light confinement coefficient in the direction perpendicular to the well layer (direction perpendicular to the main surface of the substrate) which is the light emitting layer is reduced. Therefore, when the semiconductor light emitting device oscillates laser, the operating carriers in the well layer increase, and electrons having a smaller effective mass than holes tend to overflow from the well layer to the p-side barrier layer. However, in the semiconductor light emitting device according to the present disclosure, the energy difference ΔEc between the conduction band potential energy of the p-side barrier layer and the n-side first barrier layer is large, so that the overflow of electrons can be suppressed. Therefore, while suppressing the increase in the operating voltage, it is possible to realize a semiconductor light emitting device with improved temperature characteristics compared to conventional semiconductor light emitting devices and high slope efficiency and low operating current.

[0053] In the semiconductor light emitting device according to an aspect of the present disclosure, an end face window structure may be formed on a light emitting end face portion of the active layer.

[0054] Among AlAs, GaAs, and InAs, InAs has the largest lattice constant and the smallest band gap energy. When a desired band gap energy is obtained by using an AlGaInAs-based quaternary semiconductor material for the well layer and each barrier layer as in the semiconductor light emitting device according to the present disclosure, the In content of the well layer made of AlGaInAs is higher than when a desired band gap energy is obtained by using a semiconductor material made of InGaAs for the well layer, and therefore the compressive strain of the well layer is larger.

[0055] Furthermore, when a nitride-based semiconductor material is used, InN has the largest lattice constant and the smallest band gap energy among AlN, GaN, and InN. In this case, when a desired band gap energy is obtained by using layers containing a quaternary semiconductor material made of AlGaInN for the well layer and each barrier layer, the In content of the well layer made of AlGaInN is higher than when a semiconductor material made of InGaN or AlGaN is used for the well layer, and therefore the compressive strain of the well layer is larger.

[0056] As described above, in a structure in which AlGaInAs, AlGaInN, etc. are used for the well layer and each barrier layer, when vacancies or impurities are diffused into the light-emitting end surface of the semiconductor light-emitting device, the strain energy of the well layer is reduced, so that In atoms in the well layer are easily exchanged with Al atoms and Ga atoms existing at the lattice sites of group III atoms in the stacking direction, and therefore the band gap energy of the well layer is easily increased.

[0057] As a result, the band gap energy of the well layer at the light-emitting end facet where the light density is high becomes large, forming a so-called window structure. This makes it possible to maintain a state in which the light absorption of the well layer at the light-emitting end facet is small even if the band gap energy at the light-emitting end facet becomes small due to heat generation. Therefore, it is possible to suppress the occurrence of COD (catastrophic optical damage) caused by the light absorption at the light-emitting end facet.

[0058] Furthermore, when the window structure is formed by vacancy diffusion, the occurrence of free carrier loss due to the presence of impurities can be suppressed compared to when the window structure is formed by impurity diffusion, and therefore the decrease in slope efficiency can be suppressed.

[0059] In addition, in one aspect of the semiconductor light-emitting device according to the present disclosure, the band gap energy of a portion of the active layer in which the end face window structure is formed may be greater than the band gap energy of a portion of the active layer in which the end face window structure is not formed.

[0060] This makes it possible to maintain low light absorption in the well layer of the light-emitting end facet even if the band gap energy of the light-emitting end facet decreases due to heat generation, thereby suppressing the occurrence of COD caused by light absorption by the light-emitting end facet.

[0061] In order to solve the above-mentioned problems, one aspect of a manufacturing method for a semiconductor light-emitting element according to the present disclosure includes the steps of: preparing a substrate; forming an n-type cladding layer above the substrate; forming an active layer above the n-type cladding layer; forming a p-type cladding layer above the active layer; and forming an end face window structure in the active layer, wherein the active layer has a well layer, an n-side first barrier layer disposed on the n-type cladding layer side of the well layer, and a p-side barrier layer disposed on the p-type cladding layer side of the well layer, the p-side barrier layer contains In, an In composition ratio of the n-side first barrier layer is lower than an In composition ratio of the p-side barrier layer, and a band gap energy of the n-side first barrier layer is smaller than a band gap energy of the p-side barrier layer, and vacancies or impurities are diffused into the active layer in the step of forming the end face window structure.

[0062] This makes it possible to manufacture a semiconductor light-emitting device in which the In composition ratio of the n-side first barrier layer is smaller than that of the p-side barrier layer, and the band gap of the n-side first barrier layer is smaller than that of the p-side barrier layer. With such a semiconductor light-emitting device, the energy difference ΔEc in the conduction band potential energy between the p-side barrier layer and the n-side first barrier layer can be made larger than the energy difference ΔEv in the valence band potential energy between the p-side barrier layer and the n-side first barrier layer. Therefore, it is possible to suppress the overflow of electrons from the well layer while suppressing an increase in the voltage required for the electrical conduction of holes (i.e., an increase in the operating voltage of the semiconductor light-emitting device).

[0063] Furthermore, for example, in a structure in which AlGaInAs, AlGaInN, etc. are used for the well layer and each barrier layer, when vacancies or impurities are diffused into the light-emitting end surface of the semiconductor light-emitting device, the strain energy of the well layer is reduced, so that In atoms in the well layer are easily exchanged with Al atoms and Ga atoms existing at the lattice sites of group III atoms in the stacking direction, and therefore the band gap energy of the well layer is easily increased.

[0064] As a result, the band gap energy of the well layer at the light-emitting end facet where the light density is high becomes large, and an end face window structure can be formed. This makes it possible to maintain a low light absorption state of the well layer at the light-emitting end facet even if the band gap energy at the light-emitting end facet becomes small due to heat generation. Therefore, it is possible to suppress the occurrence of COD caused by the light absorption at the light-emitting end facet. Effect of the Invention

[0065] According to the present disclosure, it is possible to provide a semiconductor light emitting device and the like that can suppress the overflow of electrons from a well layer while suppressing the operating voltage. [Brief description of the drawings]

[0066] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an overall configuration of a semiconductor light emitting device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a detailed configuration of an active layer included in the semiconductor light emitting device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing an outline of the energy band structure of an active layer according to a comparative example. [Figure 4] FIG. 4 is a schematic diagram showing an outline of the energy band structure of the active layer according to the first embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing the energy differences between the conduction band potential energy and the valence band potential energy between the n-side first barrier layer and the p-side barrier layer of the active layer according to the first embodiment. [Figure 6]FIG. 6 is a graph showing the dependence of the band gap energy (Eg) of an AlGaInAs-based material on the In and Al composition ratios. [Figure 7] FIG. 7 is a graph showing the dependence of the valence band potential energy of an AlGaInAs-based material on the In and Al composition ratios. [Figure 8] FIG. 8 is a graph showing the dependence of the conduction band potential energy of an AlGaInAs-based material on the In and Al composition ratios. [Figure 9] FIG. 9 is a graph showing the relationship between the energy difference ΔEc2 in the conduction band potential energy between an AlGaInAs-based material and Al0.2Ga0.8As, and the energy difference ΔEv2 in the valence band potential energy, and the composition of the AlGaInAs-based material. [Figure 10] FIG. 10 is a graph showing the relationship between the energy difference ΔEc2 in the conduction band potential energy between an AlGaInAs-based material and Al0.3Ga0.7As, and the energy difference ΔEv2 in the valence band potential energy, and the composition of the AlGaInAs-based material. [Figure 11] FIG. 11 is a graph showing the relationship between the energy difference ΔEc2 in the conduction band potential energy between an AlGaInAs-based material and Al0.4Ga0.6As, and the energy difference ΔEv2 in the valence band potential energy, and the composition of the AlGaInAs-based material. [Figure 12] FIG. 12 is a graph showing a simulation result of the current-voltage characteristics of the semiconductor light emitting device according to Comparative Example 1. In FIG. [Figure 13] FIG. 13 is a graph showing a simulation result of the current-voltage characteristics of the semiconductor light emitting device according to Comparative Example 2. In FIG. [Figure 14] FIG. 14 is a graph showing a simulation result of the current-voltage characteristics of the semiconductor light emitting device according to the first embodiment. [Figure 15] FIG. 15 is a graph showing the relationship between the Al composition ratio of the quaternary barrier layer and the operating voltage of each of the semiconductor light emitting devices according to Comparative Example 1, Comparative Example 2, and Embodiment 1. [Figure 16]FIG. 16 is a first graph showing calculation results of the relationship between the Al composition ratio of the well layer according to the first embodiment and the heavy hole level and the light hole level. [Figure 17] FIG. 17 is a second graph showing the calculation results of the relationship between the Al composition ratio of the well layer according to the first embodiment and the heavy hole level and the light hole level. [Figure 18] FIG. 18 is a third graph showing the calculation results of the relationship between the Al composition ratio of the well layer according to the first embodiment and the heavy hole level and the light hole level. [Figure 19] FIG. 19 is a schematic diagram showing an outline of the energy band structure of a semiconductor light emitting device according to Modification 1 of the first embodiment. In FIG. [Figure 20] FIG. 20 is a schematic diagram showing the energy differences ΔEc2 and ΔEv2 of the conduction band potential energy and the valence band potential energy between the p-side barrier layer and the p-side guide layer according to the first modification of the first embodiment. [Figure 21] FIG. 21 is a graph showing the relationship between the Al composition ratio of the p-side barrier layer and the energy differences ΔEc2 and ΔEv2 according to the first modification of the first embodiment. [Figure 22] FIG. 22 is a schematic diagram showing an outline of the energy band structure of a semiconductor light emitting device according to Modification 2 of Embodiment 1. In FIG. [Diagram 23] FIG. 23 is a schematic diagram showing an outline of the energy band structure of a semiconductor light emitting device according to Modification 3 of Embodiment 1. In FIG. [Figure 24] FIG. 24 is a schematic diagram showing an outline of the energy band structure of a semiconductor light emitting device according to the fourth modification of the first embodiment. In FIG. [Diagram 25] FIG. 25 is a schematic diagram showing an outline of the energy band structure of a semiconductor light emitting device according to Modification 5 of the first embodiment. In FIG. [Figure 26] FIG. 26 is a schematic diagram showing an outline of the energy band structure of a semiconductor light emitting device according to Modification 6 of the first embodiment. In FIG. [Figure 27] FIG. 27 is a cross-sectional view showing a configuration of a light emitting end surface portion of a semiconductor light emitting device according to Modification 7 of the first embodiment. [Figure 28] FIG. 28 is a schematic cross-sectional view showing an overall configuration of a semiconductor light emitting device according to the second embodiment. [Figure 29] FIG. 29 is a schematic cross-sectional view showing an overall configuration of a semiconductor light emitting device according to the third embodiment. [Diagram 30] FIG. 30 is a schematic cross-sectional view showing dimensions of each portion of the semiconductor light emitting device according to the third embodiment. [Diagram 31] FIG. 31 is a schematic cross-sectional view showing a mounted state of the semiconductor light emitting device according to the third embodiment. [Diagram 32] FIG. 32 is a graph showing the distribution of shear stress σxy with respect to the position in the x-axis direction in the active layer of the semiconductor light emitting device according to the third embodiment. [Diagram 33] FIG. 33 is a flowchart showing steps of a method for manufacturing a semiconductor light emitting device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, and the arrangement and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0068] In addition, each figure is a schematic diagram and is not necessarily illustrated precisely. Therefore, the scales and the like are not necessarily the same in each figure. In addition, in each figure, the same reference numerals are given to substantially the same configurations, and duplicated explanations are omitted or simplified.

[0069] 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 a stacked configuration. 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 is present between the two components, but also to the case where two components are arranged in contact with each other.

[0070] (Embodiment 1) A semiconductor light emitting device according to a first embodiment will be described.

[0071] [1-1. Overall composition] First, the overall configuration of the semiconductor light emitting device according to the present embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing the overall configuration of the semiconductor light emitting device 1 according to the present embodiment. Figure 2 is a schematic cross-sectional view showing a detailed configuration of an active layer 14 included in the semiconductor light emitting device 1 according to the present embodiment.

[0072] The semiconductor light emitting element 1 is an element that emits light when a voltage is applied. In this embodiment, the semiconductor light emitting element 1 is a semiconductor laser element that emits laser light with a wavelength of about 900 nm or more and 980 nm or less. More specifically, the semiconductor light emitting element 1 emits laser light with a wavelength of about 915 nm. FIG. 1 shows a cross section perpendicular to the resonance direction of the laser light of the semiconductor light emitting element 1. The resonator length of the semiconductor light emitting element 1, that is, the distance between the end faces in the resonance direction of the laser light, is not particularly limited, but is 2 mm or more in this embodiment. The resonator length of the semiconductor light emitting element 1 may be 4 mm or more. In this way, by increasing the resonator length, the thermal resistance of the semiconductor light emitting element 1 can be reduced, and therefore the heat dissipation can be improved. Therefore, the optical output at which the semiconductor light emitting element 1 is thermally saturated can be increased. As shown in FIG. 1, the semiconductor light-emitting element 1 includes a substrate 10, a buffer layer 11, an n-type cladding layer 12, an active layer 14, a p-type cladding layer 17, a current confinement layer 19, a contact layer 18, an n-side electrode 31, and a p-side electrode 32.

[0073] The substrate 10 is a plate-like member that serves as a base for the semiconductor light-emitting device 1. In this embodiment, the substrate 10 is an n-type GaAs substrate.

[0074] The buffer layer 11 is a layer for suppressing distortion caused by lattice mismatch between the substrate 10 and the n-type cladding layer 12. The configuration of the buffer layer 11 is not particularly limited, but in this embodiment, the buffer layer 11 is an n-type GaAs layer with a film thickness of 0.5 μm. The buffer layer 11 contains impurities with a concentration of 3×10 17 cm -3 The Si is doped.

[0075] The n-type cladding layer 12 is an n-type cladding layer disposed above the substrate 10. The n-type cladding layer 12 is a layer having a lower refractive index and a higher band gap energy than the active layer 14. The configuration of the n-type cladding layer 12 is not particularly limited, but in this embodiment, the n-type cladding layer 12 is a 4 μm-thick n-type Al 0.305 Ga 0.695 The n-type cladding layer 12 is an As layer. 18 cm -3 The Si is doped.

[0076] The active layer 14 is disposed above the n-type cladding layer 12 and is a light-emitting layer having a quantum well structure. In the present embodiment, the active layer 14 has an n-side first barrier layer 14a, a well layer 14d, and a p-side barrier layer 14f, as shown in FIG.

[0077] The well layer 14d is a quantum well layer disposed between the n-side first barrier layer 14a and the p-side barrier layer 14f. In this embodiment, the well layer 14d is an Al 0.08 Ga 0.67 In 0.25 This is the As layer.

[0078] The n-side first barrier layer 14a is a barrier layer disposed on the n-type cladding layer 12 side of the well layer 14d. In this embodiment, the n-side first barrier layer 14a is an Al 0.27 Ga0.73 This is the As layer.

[0079] The p-side barrier layer 14f is a barrier layer disposed on the p-type cladding layer 17 side of the well layer 14d. In this embodiment, the p-side barrier layer 14f is an Al 0.45 In 0.10 Ga 0.45 The thickness of the p-side barrier layer 14f is determined so that the wave function of the electrons in the well layer 14d at the end face of the p-side barrier layer 14f on the p-type cladding layer 17 side is attenuated to less than 1% of the maximum amplitude. This can suppress the electrons in the well layer 14d from passing through the p-side barrier layer 14f by the tunnel effect, that is, the generation of leakage current. The p-side barrier layer 14f has compressive strain, and lattice defects occur when the critical thickness is exceeded. Therefore, the thickness of the p-side barrier layer 14f may be 3 nm or more and less than the critical thickness so as to suppress the electrons in the well layer 14d from passing through by the tunnel effect. Here, the critical thickness can be determined as 20 / Q, where Q% is the absolute value of the lattice mismatch of the p-side barrier layer 14f with respect to the substrate 10.

[0080] The p-type cladding layer 17 is a p-type cladding layer disposed above the active layer 14. The p-type cladding layer 17 has a lower refractive index and a higher band gap energy than the active layer 14. The configuration of the p-type cladding layer 17 is not particularly limited, but in this embodiment, the p-type cladding layer 17 is a p-type Al 0.7 Ga 0.3 The p-type cladding layer 17 is an As layer. 18 cm -3 is doped with C (carbon atom).

[0081] The contact layer 18 is a layer disposed above the p-type cladding layer 17, and is in contact with the p-side electrode 32. The configuration of the contact layer 18 is not particularly limited, but in this embodiment, the contact layer 18 is a p-type GaAs layer with a film thickness of 0.4 μm. The contact layer 18 contains impurities with a concentration of 2×10 18 cm -3 is doped with C.

[0082] The current confinement layer 19 is a layer disposed above the p-type cladding layer 17, and functions to cause the current in the semiconductor light emitting device 1 to flow intensively in a narrow region, that is, to confine the current to a certain region. In this embodiment, the current confinement layer 19 is an n-type semiconductor layer disposed between the p-type cladding layer 17 and the contact layer 18. The current confinement layer 19 has an elongated opening 19a along the laser resonance direction of the semiconductor light emitting device 1. The contact layer 18 is disposed in the opening 19a. This allows the current to flow only through the opening 19a of the current confinement layer 19. In other words, the current is confined in the opening 19a. As a result, the current flows in the region of the active layer 14 below the opening 19a, and this region becomes the light emitting portion. The configuration of the current confinement layer 19 is not particularly limited, but in this embodiment, the current confinement layer 19 is an n-type GaAs layer with a film thickness of 0.25 μm. The current confinement layer 19 contains impurities of 2×10 18 cm -3 The Si is doped.

[0083] The n-side electrode 31 is an electrode disposed on the lower principal surface of the substrate 10 (i.e., the principal surface of the substrate 10 on the rear side of the principal surface on which the semiconductor layers are laminated). The configuration of the n-side electrode 31 is not particularly limited, but in this embodiment, the n-side electrode 31 includes, laminated in this order from the substrate 10 side, an AuGe film with a thickness of 90 nm, a Ni film with a thickness of 20 nm, an Au film with a thickness of 50 nm, a Ti film with a thickness of 100 nm, a Pt film with a thickness of 50 nm, a Ti film with a thickness of 50 nm, a Pt film with a thickness of 100 nm, and an Au film with a thickness of 500 nm.

[0084] The p-side electrode 32 is an electrode disposed above the contact layer 18. The p-side electrode 32 is in ohmic contact with the contact layer 18. There are no particular limitations on the configuration of the p-side electrode 32, but in this embodiment, the p-side electrode 32 includes a 50-nm-thickness Ti film, a 150-nm-thickness Pt film, and a 50-nm-thickness Au film, which are stacked in this order from the contact layer 18 side.

[0085] [1-2. Actions and Effects] Next, the operation and effects of the semiconductor light emitting element 1 according to this embodiment will be described.

[0086] [1-2-1. Actions and effects of the active layer] First, the outline of the function and effect of the active layer 14 of the semiconductor light emitting device 1 according to the present embodiment will be described with reference to Figs. 3 and 4, while comparing it with the function of a semiconductor light emitting device of a comparative example. Figs. 3 and 4 are schematic diagrams showing the outline of the energy band structure of each active layer according to the comparative example and the present embodiment, respectively. In addition, Figs. 3 and 4 also show the energy difference ΔEc between the conduction band potential energy of the p-side barrier layer and the well layer, the energy difference ΔEv between the valence band potential energy, the Fermi level Efe of electrons, and the Fermi level Efh of holes. In addition, Fig. 4 also shows the energy difference ΔEfc between the Fermi level Efe of electrons and the conduction band potential energy of the p-side barrier layer 14f, and the energy difference ΔEfv between the Fermi level Efh of holes and the valence band potential energy of the p-side barrier layer 14f.

[0087] 3 includes an n-side first barrier layer 14a, a well layer 14d, and a p-side barrier layer, similar to the active layer 14 according to the present embodiment. The composition of the p-side barrier layer of the comparative example is different from the composition of the p-side barrier layer 14f according to the present embodiment. The p-side barrier layer of the comparative example is an AlGaAs layer and does not contain In.

[0088] In the comparative active layer having such a p-side barrier layer, the case of increasing the energy difference ΔEc to suppress the overflow of electrons will be considered. In this case, the energy difference ΔEc can be increased by increasing the Al composition ratio of the p-side barrier layer. However, this increases the energy difference ΔEv. Therefore, the energy required for holes to cross the p-side barrier layer also increases, and the operating voltage of the semiconductor light emitting device increases.

[0089] On the other hand, in the active layer 14 according to the present embodiment shown in FIG. 4, the p-side barrier layer 14f contains In, and the In composition ratio of the n-side first barrier layer 14a is lower than that of the p-side barrier layer 14f. The band gap energy of the n-side first barrier layer 14a is smaller than that of the p-side barrier layer 14f. With such an active layer 14, as shown in FIG. 4, it is possible to increase the energy differences ΔEc and ΔEfc while suppressing the increase of the energy differences ΔEv and ΔEfv. Therefore, by suppressing the increase of the energy differences ΔEv and ΔEfv, it is possible to suppress the increase of the operating voltage of the semiconductor light emitting device 1, while increasing the energy differences ΔEc and ΔEfc to suppress the overflow of electrons.

[0090] The characteristics of the active layer 14 according to the present embodiment will be described in detail with reference to Figs. 5 to 8. Fig. 5 is a schematic diagram showing the energy differences between the conduction band potential energy and the valence band potential energy between the n-side first barrier layer 14a and the p-side barrier layer 14f of the active layer 14 according to the present embodiment. As shown in Fig. 5, the energy differences between the conduction band potential energy and the valence band potential energy between the n-side first barrier layer 14a and the p-side barrier layer 14f are defined as ΔEcb and ΔEvb. Figs. 6, 7, and 8 are graphs showing the In and Al composition ratio dependences of the band gap energy (Eg), valence band potential energy, and conduction band potential energy of an AlGaInAs-based material, respectively. In Figs. 6, 7, and 8, the vertical axis represents the band gap energy, valence band potential energy, and conduction band potential energy, and the horizontal axis represents the In composition ratio, respectively. Also, Figs. 6 to 8 show graphs in which the Al composition ratio is changed from 0 to 1 in increments of 0.1 as a parameter.

[0091] As shown in FIG. 6, the band gap energy decreases as the In composition ratio increases, and the band gap energy increases as the Al composition ratio increases. 0.7 In 0.3 The band gap energy of As is about 1.0 eV, and that of Al is about 1.0 eV.0.4 In 0.6 The difference between the band gap energy of As and that of As is about 1.23 eV (ΔEg shown in FIG. 6), that is, the sum of the energy differences ΔEcb and ΔEvb, is about 0.23 eV. Thus, in an AlGaInAs-based material, even if the In composition ratio is increased, the band gap energy can be increased by increasing the Al composition ratio.

[0092] As shown in Figs. 7 and 8, as the In composition ratio increases, the valence band potential energy increases and the conduction band potential energy decreases. On the other hand, as the Al composition ratio increases, the valence band potential energy decreases and the conduction band potential energy increases. In addition, the amount of change in the conduction band potential energy is greater than the amount of change in the valence band potential energy with respect to the change in the Al composition ratio and the In composition ratio. For example, in the case of Ga 0.7 In 0.3 The valence band potential energy of As is about -5.35 eV, and that of Al is about 0.4 In 0.6 The energy difference ΔE from the valence band potential energy of As is about -5.41 eV v b is approximately 0. 0 6 eV, whereas the energy difference ΔE c b is approximately 0. 1 6 eV. In this case, the energy difference ΔEcb is 2.7 times the energy difference ΔEvb. In this way, by adjusting the Al composition ratio and the In composition ratio in the AlGaInAs-based material, transmission The band potential energy is Valence electronsIt can be changed more greatly than the potential energy. Therefore, in the n-side first barrier layer 14a and the p-side barrier layer 14f, by using an AlGaInAs-based material and adjusting each composition, as shown in FIG. 4, while suppressing an increase in the energy differences ΔEv and ΔEfv, the energy differences ΔEc and ΔEfc can be increased. In the present embodiment, the In composition ratio of the n-side first barrier layer 14a is lower than the In composition ratio of the p-side barrier layer 14f, and the bandgap energy of the n-side first barrier layer 14a is smaller than the bandgap energy of the p-side barrier layer 14f. Thereby, while suppressing an increase in the energy differences ΔEv and ΔEfv, the energy differences ΔEc and ΔEfc can be increased. Therefore, it is possible to suppress an increase in the voltage required for hole conduction, that is, an increase in the operating voltage of the semiconductor light-emitting device, and suppress the overflow of electrons from the well layer.

[0093] Also, assuming that the Al composition ratio and the In composition ratio of the n-side first barrier layer 14a are ybn1 and xbn1, respectively, the composition of the n-side first barrier layer 14a is Al ybn1 Ga 1-xbn1-ybn1 In xbn1 As. Assuming that the Al composition ratio and the In composition ratio of the p-side barrier layer 14f are ybp1 and xbp1, respectively, the composition of the p-side barrier layer 14f is Al ybp1 Ga 1-xbp1-ybp1 In xbp1 As. In the present embodiment, regarding these composition ratios, the relationships 0 ≦ ybn1 ≦ 1, 0 ≦ xbn1 < 1, 0 < ybp1 < 1, 0 < xbp1 < 1, and xbn1 < xbp1 hold. By using the n-side first barrier layer 14a and the p-side barrier layer 14f having such compositions, it becomes possible to make the In composition ratio of the n-side first barrier layer 14a smaller than the In composition ratio of the p-side barrier layer 14f and make the bandgap of the n-side first barrier layer 14a smaller than the bandgap of the p-side barrier layer 14f.

[0094] In addition, in the present embodiment, with respect to the Al composition ratio, the relationship ybn1 < ybp1 holds. As a result, since the energy difference ΔEc between the conduction band potential energies of the p-side barrier layer 14f and the n-side first barrier layer 14a increases, the overflow of electrons from the well layer 14d can be further suppressed.

[0095] In addition, in the present embodiment, when the Al composition ratio and the In composition ratio of the well layer 14d are xw and yw, respectively, the composition of the well layer 14d is Al yw Ga 1-xw-yw In xw As, and the relationships 0 ≦ yw < 1 and 0 < xw < 1 hold. Thus, when the composition of the well layer 14d is Al yw Ga 1-xw-yw In xw As, by adjusting the Al composition ratio, Ga composition ratio, and In composition ratio of the well layer 14d, the magnitude of the strain in the well layer 14d and the potential energy differences between the conduction band and valence band of the well layer 14d and each barrier layer can be adjusted. Therefore, it becomes possible to adjust the oscillation wavelength of the semiconductor light-emitting device 1 and to control the overflow of electrons from the well layer 14d.

[0096] Next, the relationship between the Al composition ratio and the In composition ratio of the n-side first barrier layer 14a and the p-side barrier layer 14f according to the present embodiment will be described in more detail with reference to FIGS. 9 to 11. FIGS. 9, 10, and 11 are diagrams showing the AlGaInAs-based material and Al 0.2 Ga 0.8 As, Al 0.3 Ga 0.7 As, and Al 0.4 Ga 0.611 is a graph showing the relationship between the energy difference ΔEc2 in the conduction band potential energy between AlGaInAs and As, and the energy difference ΔEv2 in the valence band potential energy, and the composition of the AlGaInAs-based material. The horizontal and vertical axes of FIG. 9 to FIG. 11 respectively show the In composition ratio x and the Al composition ratio y of the AlGaInAs-based material. In FIG. 9 to FIG. 11, the relationship between the In composition ratio x and the Al composition ratio y at which the energy difference ΔEc2 and the energy difference ΔEv2 are predetermined values ​​is shown by a broken line and a solid line, respectively. For example, in FIG. 9, the relationship between the In composition ratio x and the Al composition ratio y at which the energy difference ΔEc2 is -50 meV, -20 meV, 0 meV, 25 meV, 50 meV, 75 meV, 100 meV, 150 meV, and 200 meV is shown by a broken line, respectively. In addition, in FIG. 9, the relationship between the In composition ratio x and the Al composition ratio y where the energy difference ΔEv2 is −40 meV, −20 meV, 0 meV, 30 meV, 40 meV, 60 meV, 80 meV, and 100 meV is shown by solid lines.

[0097] For example, in order to suppress the overflow of electrons from the well layer 14d, Al 0.2 Ga 0.8 The n-side first barrier layer 14a is made of As, and the Al y Ga 1-x-y In x In order to set the energy difference in conduction band potential energy with the p-side barrier layer 14f made of As to be 25 meV or more, it is sufficient to adopt the In composition ratio x and the Al composition ratio y corresponding to points on and in the region above the straight line y=0.4x+0.225 where ΔEc2 is 25 meV as shown in Fig. 9. In other words, it is sufficient that the In composition ratio x and the Al composition ratio y satisfy the relationship y≧0.4x+0.225.

[0098] In order to suppress an increase in the operating voltage of the semiconductor light emitting device 1, Al 0.2 Ga 0.8 The n-side first barrier layer 14a is made of As, and the Al y Ga 1-x-y In xIn order to set the energy difference in valence band potential energy with the p-side barrier layer 14f made of As to 30 meV or less, it is sufficient to adopt the In composition ratio x and the Al composition ratio y corresponding to the points on and below the line y=x+0.265 where ΔEv2 is 30 meV as shown in Fig. 9. In other words, it is sufficient that the relationship y≦x+0.265 is satisfied for the In composition ratio x and the Al composition ratio y.

[0099] In order to further suppress the increase in the operating voltage of the semiconductor light emitting device 1, Al 0.2 Ga 0.8 The n-side first barrier layer 14a is made of As, and the Al y Ga 1-x-y In x In order to make the energy difference in the valence band potential energy with the p-side barrier layer 14f made of As 0 meV or less, the In composition ratio x and the Al composition ratio y may satisfy the relationship y≦x+0.2 as shown in FIG. 9. In addition, in order to further suppress the overflow of electrons from the well layer 14d, the Al 0.2 Ga 0.8 The n-side first barrier layer 14a is made of As, and the Al y Ga 1-x-y In x In order to make the conduction band potential energy difference with the p-side barrier layer 14f made of As 50 meV or more, the In composition ratio x and the Al composition ratio y need to satisfy the relationship y≧0.4x+0.255 as shown in FIG.

[0100] Therefore, Al 0.2 Ga 0.8 When the n-side first barrier layer 14a made of As is used, in order to suppress an increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2≦30 meV) while suppressing the overflow of electrons from the well layer 14d (ΔEc2≧25 meV), y Ga 1-x-y In xThe In composition ratio x and the Al composition ratio y of the p-side barrier layer 14f made of As may satisfy the relationships y≧0.4x+0.225 and y≦x+0.265. The combination of the In composition ratio x and the Al composition ratio y for which this relationship holds corresponds to the points in the hatched area shown in FIG. 9. In addition, in order to further suppress the increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2≦0 meV), the relationship y≦x+0.2 may also hold. The combination of the In composition ratio x and the Al composition ratio y for which this relationship holds corresponds to the points in the area hatched more densely with dots among the hatched areas shown in FIG. In addition, in order to further suppress the overflow of electrons from the well layer 14d (ΔEc2≧50 meV), the relationship y≧0.4x+0.255 may also hold.

[0101] Al 0.3 Ga 0.7 Even when the n-side first barrier layer 14a made of As is used, 0.2 Ga 0.8 As in the case of using the n-side first barrier layer 14a made of As, the composition of the p-side barrier layer 14f can be determined from the graph shown in Fig. 10. That is, in order to suppress the overflow of electrons from the well layer 14d (ΔEc2 ≧ 25 meV) while suppressing an increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2 ≦ 30 meV), as shown in Fig. 10, y Ga 1-x-y In xThe In composition ratio x and the Al composition ratio y of the p-side barrier layer 14f made of As may satisfy the relationships y≧0.4x+0.32 and y≦x+0.36. The combination of the In composition ratio x and the Al composition ratio y for which this relationship holds corresponds to the points in the hatched area shown in FIG. 10. In addition, in order to further suppress the increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2≦0 meV), the relationship y≦x+0.3 may hold. The combination of the In composition ratio x and the Al composition ratio y for which this relationship holds corresponds to the points in the area hatched more densely with dots among the hatched areas shown in FIG. In addition, in order to further suppress the overflow of electrons from the well layer 14d (ΔEc2≧50 meV), the relationship y≧0.4x+0.355 may hold.

[0102] Al 0.4 Ga 0.6 Even when the n-side first barrier layer 14a made of As is used, 0.2 Ga 0.8 As in the case of using the n-side first barrier layer 14a made of As, the composition of the p-side barrier layer 14f can be determined from the graph shown in Fig. 11. That is, in order to suppress the overflow of electrons from the well layer 14d (ΔEc2 ≧ 25 meV) while suppressing an increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2 ≦ 30 meV), as shown in Fig. 11, y Ga 1-x-y In xThe In composition ratio x and the Al composition ratio y of the p-side barrier layer 14f made of As may satisfy the relationships y≧0.4x+0.42 and y≦x+0.46. The combination of the In composition ratio x and the Al composition ratio y for which this relationship holds corresponds to the points in the hatched area shown in FIG. 11. In order to further suppress the increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2≦0 meV), the relationship y≦x+0.4 may also hold. The combination of the In composition ratio x and the Al composition ratio y for which this relationship holds corresponds to the points in the area hatched more densely with dots among the hatched areas shown in FIG. 11. In order to further suppress the overflow of electrons from the well layer 14d (ΔEc2≧50 meV), the relationship y≧0.4x+0.45 may also hold.

[0103] To summarize the relationships shown in FIGS. 9 to 11, the composition of the n-side first barrier layer 14a is Al ybn1 Ga 1-xbn1-ybn1 In xbn1 The composition of the p-side barrier layer 14f is represented by Al ybp1 Ga 1-xbp1-ybp1 In xbp1 Expressed in As, 0.2≦ybn1≦0.4 ybp1≦xbp1+0.975ybn1+0.069, ybp1≧0.4xbp1+0.975ybn1+0.029, and xbp1≦0.15 may hold. This makes it possible to suppress the overflow of electrons from the well layer 14d (ΔEc2≧25 meV) while suppressing an increase in the operating voltage of the semiconductor light emitting element 1 (ΔEv2≦30 meV). In addition, by setting the Al composition ratio ybn1 of the n-side first barrier layer 14a to 0.2 or more and 0.4 or less, the light distribution in the vertical direction can be controlled with high precision, and a significant decrease in the light confinement factor can be suppressed while reducing the loss of the waveguide.

[0104] Furthermore, ybp1≦xbp1+0.975ybn1+0.049 This can further suppress an increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2≦20 meV).

[0105] Furthermore, ybp1≦xbp1+ybn1 This can further suppress an increase in the operating voltage of the semiconductor light emitting device 1 (ΔEv2≦0 meV).

[0106] Furthermore, ybp1≧0.4xbp1+0.975ybn1+0.061 This can further suppress the overflow of electrons from the well layer 14d (ΔEc2≧50 meV).

[0107] [1-2-2. Function and effect of the cladding layer] Next, the functions and effects of the n-type cladding layer 12 and the p-type cladding layer 17 according to this embodiment will be described.

[0108] The band gap energy of the n-type cladding layer 12 according to this embodiment is smaller than the band gap energy of the p-type cladding layer 17. This makes the refractive index of the n-type cladding layer 12 higher than the refractive index of the p-type cladding layer 17. As a result, the light distribution in the direction perpendicular to the main surface of the substrate 10 is biased toward the n-type cladding layer 12 side. Here, in the n-type semiconductor layer, the doping concentration of the n-type impurity is set to 1×10 16 cm -3 That's it, 1×10 18 cm -3 The resistance value can be suppressed by setting the doping concentration of p-type impurities in the p-type semiconductor layer to the following range: 18 cm -3 If the resistance is not set to this value, the resistance value cannot be suppressed. Therefore, the free carrier loss that light receives from the waveguide of the semiconductor light emitting element 1 is larger in the p-type semiconductor layer, which has a higher doping concentration than the n-type semiconductor layer. Therefore, by biasing the light distribution toward the n-type cladding layer 12 as in the semiconductor light emitting element 1 according to this embodiment, the waveguide loss can be reduced.

[0109] Since the light distribution is biased toward the n-type cladding layer 12 side, the light confinement factor in the vertical direction (the direction perpendicular to the main surface of the substrate) to the well layer 14d, which is the light-emitting layer, decreases. Therefore, when laser oscillation occurs in the semiconductor light-emitting device 1, the operating carriers in the well layer 14d increase, and electrons with a smaller effective mass than holes tend to overflow from the well layer 14d to the p-side barrier layer 14f. However, in the semiconductor light-emitting device 1 according to the present embodiment, since the energy difference ΔEc between the conduction band potential energies of the p-side barrier layer 14f and the n-side first barrier layer 14a is large, the overflow of electrons can be suppressed. Therefore, it is possible to improve the temperature characteristics compared to conventional semiconductor light-emitting devices while suppressing an increase in the operating voltage, and to realize a semiconductor light-emitting device with a low operating current and a high slope efficiency.

[0110] Also, when the Al composition ratio of the n-type cladding layer 12 is yn1, the composition of the n-type cladding layer 12 is represented by Al yn1 Ga 1-yn1 As, and when the Al composition ratio of the p-type cladding layer 17 is yp1, the composition of the p-type cladding layer 17 is represented by Al yp1 Ga 1-yp1 As, and the relationship 0 < yn1 < yp1 < 1 holds.

[0111] Thus, since the Al composition ratio yn1 of the n-type cladding layer 12 is smaller than the Al composition ratio yp1 of the p-type cladding layer 17, the refractive index of the n-type cladding layer 12 becomes larger than the refractive index of the p-type cladding layer 17. Along with this, the light distribution in the vertical direction is biased toward the n-type cladding layer 12 side. As described above, since the free carrier loss that light receives from the waveguide of the semiconductor light-emitting device 1 increases in the p-type semiconductor layer having a higher doping concentration than the n-type semiconductor layer, it is possible to reduce the waveguide loss by making the vertical light distribution closer to the n-type semiconductor layer.

[0112] Since the light distribution is biased toward the n-type cladding layer 12 side, the light confinement coefficient in the direction perpendicular to the well layer 14d, which is the light emitting layer, decreases, and as described above, electrons are more likely to overflow from the well layer 14d to the p-side barrier layer 14f. However, in the semiconductor light emitting device 1 according to the present embodiment, the energy difference ΔEc between the conduction band potential energy of the p-side barrier layer 14f and the n-side first barrier layer 14a is large, so that the overflow of electrons can be suppressed. Therefore, while suppressing an increase in the operating voltage, it is possible to realize a semiconductor light emitting device 1 with improved temperature characteristics and high slope efficiency and low operating current.

[0113] [1-2-3. Current-voltage characteristics] Next, the current-voltage characteristics of the semiconductor light emitting device 1 according to the present embodiment will be described with reference to Figs. 12 to 15 in comparison with a comparative example. Figs. 12, 13, and 14 are graphs showing simulation results of the current-voltage characteristics of the semiconductor light emitting devices according to Comparative Example 1, Comparative Example 2, and the present embodiment, respectively. In each of the graphs of Figs. 12 to 14, the horizontal axis and the vertical axis show the voltage and current applied to the semiconductor light emitting device, respectively. Fig. 15 is a graph showing the relationship between the Al composition ratio of the quaternary barrier layer of each of the semiconductor light emitting devices according to Comparative Example 1, Comparative Example 2, and the present embodiment, and the operating voltage. The horizontal axis of the graph in Fig. 15 shows the Al composition ratio of the quaternary barrier layer, and the vertical axis shows the operating voltage. The operating voltage shown in Fig. 15 shows the operating voltage when the operating current (i.e., the current applied to the semiconductor light emitting device) is 8A.

[0114] The semiconductor light emitting device of Comparative Example 1 is different from the semiconductor light emitting device 1 according to the present embodiment in that the n-side first barrier layer and the p-side barrier layer are the same quaternary barrier layer, that is, barrier layers formed of an AlGaInAs-based material. 0.4 Ga 0.5 In 0.1 As, Al 0.45 Ga 0.45 In 0.1 As, Al 0.5 Ga 0.4 In 0.1 As and Al 0.55Ga 0.35 In 0.1 As was used. Also, in Fig. 12, the composition is Al 0.3 Ga 0.7 The simulation results for the case where a ternary barrier layer made of As is used are also shown. The composition of the well layer is Al 0.04 Ga 0.77 In 0.19 As.

[0115] The semiconductor light emitting device of Comparative Example 2 differs from the semiconductor light emitting device 1 according to the present embodiment in that only the n-side first barrier layer is a quaternary barrier layer similar to that of Comparative Example 1, and the p-side barrier layer is a ternary barrier layer. 0.3 Ga 0.7 In addition, in FIG. 13, the composition of the n-side first barrier layer is Al. 0.3 Ga 0.7 The simulation results for the case where a ternary barrier layer made of As is used are also shown. The composition of the well layer is the same as in Comparative Example 1, with Al 0.04 Ga 0.77 In 0.19 As.

[0116] In the semiconductor light emitting device 1 according to the present embodiment, only the p-side barrier layer 14f is a quaternary barrier layer similar to that in Comparative Example 1, and the n-side first barrier layer 14a has a composition of Al 0.3 Ga 0.7 In addition, in FIG. 14, the p-side barrier layer 14f has a composition of Al 0.3 Ga 0.7 The simulation results for the case where a ternary barrier layer made of As is used are also shown. In addition, the composition of the well layer 14d is the same as that of Comparative Example 1 and Comparative Example 2. 0.04 Ga 0.77 In 0.19 As.

[0117] 12 to 15, in the semiconductor light emitting device 1 according to this embodiment, the operating voltage can be reduced compared to the semiconductor light emitting devices of Comparative Example 1 and Comparative Example 2. In particular, the effect of reducing the operating voltage becomes more significant as the Al composition ratio in the quaternary barrier layer increases. In the semiconductor light emitting device 1 according to this embodiment, the increase in the operating voltage can be suppressed even if the Al composition ratio of the p-side barrier layer 14f varies, so that the degree of freedom in controlling the composition of the p-side barrier layer 14f can be increased. This allows the yield in manufacturing the semiconductor light emitting device 1 to be improved.

[0118] Furthermore, in the semiconductor light-emitting device 1 according to this embodiment, only the p-side barrier layer 14f is a quaternary barrier layer, and therefore the increase in operating voltage caused by composition variations in each barrier layer can be suppressed more effectively than in the case where both the n-side first barrier layer 14a and the p-side barrier layer 14f are quaternary barrier layers.

[0119] [1-2-4. Polarization ratio increase effect] Next, the effect of increasing the polarization ratio (the ratio of the intensity of TE mode light to the intensity of TM mode light) according to this embodiment will be described.

[0120] In semiconductor light-emitting devices, the polarization ratio decreases when light holes and electrons recombine to generate TM mode light. In addition, during high-output operation of conventional semiconductor light-emitting devices, the active layer temperature and operating carrier density increase, increasing the number of light holes and the TM mode light component, which reduces the polarization ratio.

[0121] In addition, when the cavity length of the semiconductor light emitting element is increased, the contact area with the submount on which the semiconductor light emitting element is mounted increases. This increases the influence of distortion caused by warping of the semiconductor light emitting element and unevenness of the solder used for mounting on the active layer. This may cause a change in the energy band structure of the active layer, increasing the number of light holes.

[0122] Therefore, in this embodiment, the compressive strain of the well layer 14d is increased to increase the energy difference between the ground level of the light holes and the ground level of the heavy holes. This reduces the number of holes present in the light holes, and reduces the recombination probability between the light holes and electrons. Hereinafter, the relationship between the heavy hole level and the light hole level of the well layer 14d according to this embodiment and the composition of the well layer 14d will be described with reference to FIGS. 16 to 18.

[0123] 16 to 18 are graphs showing the calculation results of the relationship between the Al composition ratio of the well layer 14d according to the present embodiment and the heavy hole (HH) level and the light hole (LH) level. Below the graph in each figure is a table showing the combinations of the Al composition ratio and the In composition ratio used in the calculation and the lattice mismatch corresponding to each combination. FIGS. 16 to 18 show the relationship when different n-side first barrier layer 14a and p-side barrier layer 14f are used. In FIG. 16, Al 0.24 Ga 0.76 As and Al 0.35 Ga 0.55 In 0.1 FIG. 17 shows the relationship when As is used as the n-side first barrier layer 14a and the p-side barrier layer 14f. 0.27 Ga 0.73 As and Al 0.37 Ga 0.53 In 0.1 FIG. 18 shows the relationship when As is used as the n-side first barrier layer 14a and the p-side barrier layer 14f. 0.3 Ga 0.7 As and Al 0.4 Ga 0.5 In 0.1 The relationship shown is for the case where As is used. Also, an AlGaInAs-based quaternary semiconductor material film is used as the well layer 14d.

[0124] In this embodiment, since the substrate 10 of the semiconductor light-emitting element 1 is a GaAs substrate, when an AlGaInAs-based quaternary semiconductor material is used for each barrier layer and well layer 14d, it is possible to generate compressive strain in the well layer 14d. When the well layer 14d has compressive strain, the number of light holes formed in the valence band of the well layer 14d can be reduced by adjusting the composition of the well layer 14d. Therefore, since the recombination probability between the light hole and the electron can be reduced, the polarization ratio of the output light from the semiconductor light-emitting element can be increased.

[0125] As shown in each of the tables in FIGS. 16 to 18, by increasing the Al composition ratio of the well layer 14d, the lattice mismatch of the well layer 14d can be increased, that is, the compressive strain of the well layer 14d can be increased. As a result, as shown in each of the graphs in FIGS. 16 to 18, the energy difference between the heavy hole ground level (HH1) and the light hole ground level (LH1) can be increased. For example, when the composition of the well layer 14d is represented as Al yw Ga 1-xw-yw In xw As, the relationships of 0 < yw < 1 and 0 < xw < 1 may be satisfied. Thus, when the well layer 14d contains Al, when the well layer 14d has compressive strain, the number of light holes formed in the valence band of the well layer can be reduced. Therefore, by reducing the number of light holes formed in the valence band of the well layer, the recombination probability between the light hole and the electron can be reduced, so that the polarization ratio (the ratio of the intensity of the TE mode light to the intensity of the TM mode light) of the output light from the semiconductor light-emitting element can be increased.

[0126] In the examples shown in Figs. 16 to 18, the Al composition ratio of the well layer 14d may be set to an Al composition ratio such that a higher-order light hole level (such as LH2 shown in Figs. 17 and 18) other than the ground level (LH1) of the light hole does not appear. For example, in the example shown in Fig. 16, the Al composition ratio may be 0 or more, in the example shown in Fig. 17, the Al composition ratio may be about 0.005 or more, and in the example shown in Fig. 18, the Al composition ratio may be about 0.03 or more. As shown in Figs. 16 to 18, a region of the Al composition ratio in which a higher-order light hole level other than the ground level (LH1) of the light hole is not formed is set as the composition ratio setting region.

[0127] By determining the composition of the well layer 14d as described above, the polarization ratio of the semiconductor light emitting element 1 can be increased.

[0128] [1-3. Variation 1] Next, a semiconductor light emitting device according to Modification 1 of the present embodiment will be described with reference to Figs. 19 to 21. Fig. 19 is a schematic diagram showing an overview of the energy band structure of a semiconductor light emitting device 1a according to this modification. Fig. 20 is a schematic diagram showing the energy differences ΔEc2 and ΔEv2 of the conduction band potential energy and the valence band potential energy between the p-side barrier layer 14f and the p-side guide layer 14g according to this modification. Fig. 21 is a graph showing the relationship between the Al composition ratio of the p-side barrier layer 14f according to this modification and the energy differences ΔEc2 and ΔEv2.

[0129] 19, the semiconductor light emitting device 1a according to this modification further includes a p-side guide layer 14g disposed between the p-side barrier layer 14f and the p-type cladding layer 17 and having a refractive index higher than that of the p-type cladding layer 17. In this modification, the p-side guide layer 14g is an Al 0.27 Ga 0.73The p-side guide layer 14g is an As film. By providing the semiconductor light emitting element 1a with such a p-side guide layer 14g, the light distribution in the vertical direction can be controlled with high precision, and the light distribution can be prevented from being too biased toward the n-type semiconductor layer side (i.e., the n-type cladding layer 12 side). Therefore, the light confinement coefficient in the vertical direction to the well layer 14d can be prevented from becoming small, and the operating carrier density in the well layer 14d can be prevented from increasing. In other words, the temperature characteristics of the semiconductor light emitting element 1a can be prevented from deteriorating. Furthermore, if the p-side guide layer 14g is undoped, the increase in free carrier loss due to impurity doping can be prevented, and therefore the loss of the waveguide can be reduced. As a result, a semiconductor laser element with excellent temperature characteristics and high slope efficiency can be realized.

[0130] As shown in Fig. 20, when the energy differences in the conduction band potential energy and the valence band potential energy between the p-side barrier layer 14f and the p-side guide layer 14g are expressed as ΔEc2 and ΔEv2, respectively, the relationship between the Al composition ratio of the p-side barrier layer 14f and the energy differences ΔEc2 and ΔEv2 is as shown in the graph in Fig. 21. Here, the composition of the p-side guide layer 14g is Al 0.3 Ga 0.7 The In composition ratio of the p-side barrier layer 14f is fixed at 0.1.

[0131] In order to suppress the generation of electrons leaking from the well layer 14d to the p-side guide layer 14g while making the refractive index of the p-side guide layer 14g sufficiently large, the energy difference ΔEc2 of the conduction band potential energy may be 40 meV or more. In this case, as shown in FIG. 21, the Al composition ratio of the p-side barrier layer 14f may be about 0.38 or more. In addition, in order to suppress the increase in the operating voltage of the semiconductor light emitting device 1a by suppressing the energy required to supply holes to the well layer 14d, the energy difference ΔEv2 may be 30 meV or less. In this case, as shown in FIG. 21, the Al composition ratio of the p-side barrier layer 14f may be about 0.48 or less.

[0132] Similarly to the relationship between the Al composition ratio and the In composition ratio of the p-side barrier layer 14f, the relationship between the Al composition ratio of the p-side guide layer 14g and the Al composition ratio and the In composition ratio of the p-side barrier layer 14f can also be determined using Figures 9 to 11. If the Al composition ratio of the p-side guide layer 14g is ygp1, the composition of the p-side guide layer 14g is ygp1 Ga 1-ygp1 Assuming that the Al composition ratio and the In composition ratio of the p-side barrier layer 14f are ybp1 and xbp1, respectively, ybp1≦xbp1+0.975ygp1+0.069, ybp1≧0.4xbp1+0.975ygp1+0.029, and 0.2≦ygp1≦0.4 The following relationship may be satisfied.

[0133] The p-side guide layer 14g having such a composition is nearly lattice-matched to the GaAs substrate 10. This allows the thickness of the p-side barrier layer 14f having compressive lattice mismatch to be equal to or smaller than the critical thickness. This makes it possible to suppress deterioration of the crystallinity of the p-side barrier layer 14f.

[0134] Furthermore, when the well layer 14d is a quaternary semiconductor material film containing Al, the compressive strain in the active layer 14 increases. For this reason, the p-side guide layer 14g, which is nearly lattice-matched with the GaAs substrate, is disposed above the p-side barrier layer 14f, so that the accumulation of compressive strain near the active layer 14 can be suppressed. In this case, the potential energy between the ground levels of the heavy holes and the light holes increases, so that the probability of recombination between the light holes and the electrons can be reduced. Therefore, the TM polarization component caused by the recombination between the light holes and the electrons can be reduced, and the polarization ratio is improved.

[0135] In addition, since the above relationship is satisfied, the energy difference ΔEv2 in the valence band potential energy between the p-side barrier layer 14f and the p-side guide layer 14g can be suppressed to 30 meV or less while the energy difference ΔEc2 in the conduction band potential energy can be increased to 25 meV or more. As a result, the overflow of electrons from the well layer can be suppressed while suppressing an increase in the operating voltage.

[0136] Furthermore, by setting the Al composition ratio ygp1 of the p-side guide layer 14g to be greater than or equal to 0.2 and less than or equal to 0.4, the light distribution in the vertical direction can be controlled with even greater precision, making it possible to reduce loss in the waveguide while suppressing a significant decrease in the light confinement factor.

[0137] [1-4. Variation 2] Next, a semiconductor light emitting device according to Modification 2 of the present embodiment will be described with reference to Fig. 22. Fig. 22 is a schematic diagram showing an overview of the energy band structure of a semiconductor light emitting device 1b according to this modification.

[0138] 22, the semiconductor light emitting device 1b according to this modification further includes a p-side intermediate layer 14e in addition to the components of the semiconductor light emitting device 1a according to the first modification. The p-side intermediate layer 14e is a semiconductor layer disposed between the well layer 14d and the p-side barrier layer 14f. In this modification, the p-side intermediate layer 14e is a 3 nm-thick Al 0.27 Ga 0.73 The p-side intermediate layer 14e is an As film. The p-side intermediate layer 14e is a layer that is thin enough that electrons supplied to the well layer 14d can seep out to the p-side barrier layer 14f side.

[0139] If the Al composition ratio of the p-side intermediate layer 14e is ykp1, the composition of the p-side intermediate layer 14e is Al ykp1 Ga 1-ykp1 Assuming that the Al composition ratio and the In composition ratio of the p-side barrier layer 14f are ybp1 and xbp1, respectively, ybp1≦xbp1+0.975ykp1+0.069, ybp1≧0.4xbp1+0.975ykp1+0.029, and 0.2≦ykp1≦0.4 The following relationship may be satisfied.

[0140] 9 to 11, when the above relationship is satisfied for the Al composition ratio ybp1 of the p-side barrier layer 14f, the energy difference ΔEc2 in the conduction band potential energy between the p-side barrier layer 14f and the p-side intermediate layer 14e is 25 meV or more, and the energy difference ΔEv2 in the valence band potential energy is 30 meV or less. This makes it possible to suppress the prevention of the injection of holes into the well layer 14d, thereby suppressing an increase in the operating voltage. In addition, it is possible to suppress the overflow of electrons from the well layer 14d.

[0141] Furthermore, by setting the Al composition ratio of the p-side intermediate layer 14e to be 0.2 or more and 0.4 or less, the light distribution in the vertical direction can be controlled with even higher precision, and the optical confinement factor can be increased while reducing loss in the waveguide.

[0142] In addition, by disposing the p-side intermediate layer 14e made of an AlGaAs layer that is approximately lattice-matched to the GaAs substrate between the well layer 14d and the p-side barrier layer 14f, the region in which compressive strain is formed in the vicinity of the active layer 14 can be dispersed, thereby suppressing the deterioration of crystallinity due to the concentration of compressive strain.

[0143] Furthermore, since the energy difference in valence band potential energy between the well layer 14d and the p-side intermediate layer 14e can be reduced, the formation of high-level light holes can be suppressed, and therefore the decrease in the polarization ratio can be suppressed.

[0144] [1-5. Variation 3] Next, a semiconductor light emitting device according to Modification 3 of the present embodiment will be described with reference to Fig. 23. Fig. 23 is a schematic diagram showing an overview of the energy band structure of a semiconductor light emitting device 1c according to this modification.

[0145] 23, the semiconductor light emitting device 1c according to this modification further includes an n-side second barrier layer 14b in addition to the components of the semiconductor light emitting device 1a according to the first modification. The n-side second barrier layer 14b is a semiconductor layer disposed between the n-side first barrier layer 14a and the well layer 14d. In this modification, the n-side second barrier layer 14b is a 7 nm-thick Al0.31 Ga 0.66 In 0.03 It is an As film.

[0146] When the Al composition ratio and the In composition ratio of the n-side second barrier layer 14b are ybn2 and xbn2, respectively, the composition of the n-side second barrier layer 14b is Al ybn2 Ga 1-xbn2-ybn2 In xbn2 It is represented by As, ybn2 ≥ xbn2 + ybn1, ybn2≦0.4xbn2+0.975ybn1+0.061, xbn2≦0.15, and 0.2≦ybn1≦0.35 The following relationship may be satisfied.

[0147] When the above relationship is satisfied for the Al composition ratio ybn2 of the n-side second barrier layer 14b, the energy difference ΔEc2 in the conduction band potential energy between the n-side first barrier layer 14a and the n-side second barrier layer 14b is 50 meV or less, and the energy difference ΔEv2 in the valence band potential energy is 30 meV or more. This makes it possible to suppress the prevention of the injection of electrons into the well layer 14d, thereby suppressing an increase in the operating voltage. In addition, it is possible to suppress the overflow of holes from the well layer 14d.

[0148] In addition, by lowering the Al composition ratio of the n-side first barrier layer 14a to 0.2 or more and 0.35 or less, the refractive index of the n-side first barrier layer 14a can be increased, which makes it easier to shift the light distribution in the vertical direction toward the n-type semiconductor layer side, thereby facilitating the reduction of loss in the waveguide.

[0149] [1-6. Variation 4] Next, a semiconductor light emitting device according to Modification 4 of this embodiment will be described with reference to Fig. 24. Fig. 24 is a schematic diagram showing an overview of the energy band structure of a semiconductor light emitting device 1d according to this modification.

[0150] 24, the semiconductor light emitting device 1d according to this modification further includes a p-side intermediate layer 14e and an n-side third barrier layer 14c in addition to the components of the semiconductor light emitting device 1c according to the third modification. The n-side third barrier layer 14c is a semiconductor layer disposed between the well layer 14d and the n-side second barrier layer 14b. In this modification, the n-side third barrier layer 14c is a 3 nm-thick Al 0.27 Ga 0.73 The n-side third barrier layer 14c is an As film. The n-side third barrier layer 14c is a layer that is thin enough that electrons supplied to the well layer 14d seep out toward the n-side second barrier layer 14b.

[0151] When the Al composition ratio of the n-side third barrier layer 14c is ybn3, the composition of the n-side third barrier layer 14c is Al ybn3 Ga 1-ybn3 Here, when the Al composition ratio and the In composition ratio of the n-side second barrier layer 14b are denoted as ybn2 and xbn2, respectively, ybn2 ≥ xbn2 + ybn3, ybn2≦0.4xbn2+0.975ybn3+0.061, and 0.2≦ybn3≦0.35 The following relationship may be satisfied.

[0152] When the above relationship is satisfied for the Al composition ratio ybn2 of the n-side second barrier layer 14b, the energy difference ΔEc2 of the conduction band potential energy between the n-side second barrier layer 14b and the n-side third barrier layer 14c is 50 meV or less. In addition, by setting the Al composition ratio of the n-side third barrier layer 14c to 0.35 or less, the band gap energy of the n-side third barrier layer 14c can be reduced. Therefore, the prevention of the injection of electrons into the well layer 14d can be suppressed, and an increase in the operating voltage can be suppressed.

[0153] When the above relationship is satisfied for the Al composition ratio ybn2 of the n-side second barrier layer 14b, the energy difference ΔEv2 in the valence band potential energy between the n-side second barrier layer 14b and the n-side third barrier layer 14c is 0 meV or more. Therefore, the overflow of holes from the well layer 14d can be suppressed.

[0154] In addition, by lowering the Al composition ratio of the n-side third barrier layer 14c to 0.2 or more and 0.35 or less, the refractive index of the n-side third barrier layer 14c can be increased, which makes it easier to shift the light distribution in the vertical direction toward the n-type semiconductor layer side, thereby facilitating the reduction of loss in the waveguide.

[0155] [1-7. Variation 5] Next, a semiconductor light emitting device according to Modification 5 of the present embodiment will be described with reference to Fig. 25. Fig. 25 is a schematic diagram showing an overview of the energy band structure of a semiconductor light emitting device 1e according to this modification.

[0156] 25, a semiconductor light emitting device 1e according to this modification has a multiple quantum well structure. The active layer of the semiconductor light emitting device 1e has an n-side first barrier layer 14a, a first intermediate barrier layer 14h, a p-side barrier layer 14f, and two well layers 14d.

[0157] The first intermediate barrier layer 14h is a barrier layer disposed between the n-side first barrier layer 14a and the p-side barrier layer 14f. In this modification, the first intermediate barrier layer 14h is an Al 0.3 Ga 0.7 It is an As film.

[0158] One of the two well layers 14d is an example of a first well layer disposed between the n-side first barrier layer 14a and the first intermediate barrier layer 14h. The other of the two well layers 14d is an example of a second well layer disposed between the first intermediate barrier layer 14h and the p-side barrier layer 14f. In this modification, each of the two well layers 14d is an example of a 6 nm-thick Al 0.08 Ga 0.67 In 0.25 It is an As film.

[0159] In the semiconductor light emitting device 1e having a multiple quantum well structure as in this modified example, an increase in the operating voltage can also be suppressed, and the overflow of electrons can also be suppressed in the p-side barrier layer 14f.

[0160] In addition, the semiconductor light emitting device 1e according to this modification includes two well layers 14d, but the number of well layers 14d is not limited to two. The number of well layers 14d may be three or more. When the semiconductor light emitting device 1e includes N well layers 14d (N is an integer of 2 or more), the semiconductor light emitting device 1e includes (N-1) intermediate barrier layers from the first intermediate barrier layer to the (N-1)th intermediate barrier layer. Here, when the Al composition ratio and In composition ratio of the kth intermediate barrier layer (k=1, 2, 3, . . . , N-1) are ybk and xbk (k=1, 2, 3, . . . , N-1), respectively, the composition of the kth intermediate barrier layer is Al. ybk Ga 1-xbk-ybk In xbk As, where ybn1≦ybk≦ybp1, and xbn1≦xbk≦xbp1 holds, and the band gap energy of the kth intermediate barrier layer is equal to or greater than the band gap energy of the n-side first barrier layer 14a and equal to or less than the band gap energy of the p-side barrier layer 14f.

[0161] This provides the same effects as the semiconductor light emitting device 1 according to the present embodiment. In addition, by adopting a multiple quantum well structure, the operating carrier density in the laser oscillation state in each well layer can be reduced, so that the overflow of electrons can be further suppressed. Therefore, the temperature characteristic of the semiconductor light emitting device 1e is further improved.

[0162] [1-8. Variation 6] Next, a semiconductor light emitting device according to Modification 6 of this embodiment will be described with reference to Fig. 26. Fig. 26 is a schematic diagram showing an overview of the energy band structure of a semiconductor light emitting device 1f according to this modification.

[0163] 26, a semiconductor light emitting device 1f according to this modification has a multiple quantum well structure. The active layer of the semiconductor light emitting device 1f has an n-side first barrier layer 14a, a first intermediate barrier layer 14ha, a p-side barrier layer 14f, and two well layers 14d.

[0164] The first intermediate barrier layer 14ha in this modification is a barrier layer disposed between the n-side first barrier layer 14a and the p-side barrier layer 14f, similar to the first intermediate barrier layer 14h in the modification 5. In this modification, the first intermediate barrier layer 14ha has a first intermediate n-side barrier layer 14i and a first intermediate p-side barrier layer 14j.

[0165] The first intermediate n-side barrier layer 14i is a layer of the first intermediate barrier layer 14ha that is disposed on the n-side first barrier layer 14a side. In this modification, the first intermediate n-side barrier layer 14i is an Al 0.3 Ga 0.7 It is an As film.

[0166] The first intermediate p-side barrier layer 14j is a layer of the first intermediate barrier layer 14ha that is disposed on the p-side barrier layer 14f side. In this modification, the first intermediate p-side barrier layer 14j is an Al 0.45 Ga 0.45 In 0.1 It is an As film.

[0167] One of the two well layers 14d is an example of a first well layer disposed between the n-side first barrier layer 14a and the first intermediate barrier layer 14ha. The other of the two well layers 14d is an example of a second well layer disposed between the first intermediate barrier layer 14ha and the p-side barrier layer 14f. In this modification, each of the two well layers 14d is an example of a 6 nm-thick Al 0.08 Ga 0.67 In 0.25 It is an As film.

[0168] In the semiconductor light emitting device 1f having a multiple quantum well structure as in this modified example, the increase in the operating voltage can also be suppressed, and the overflow of electrons can also be suppressed in the p-side barrier layer 14f.

[0169] In addition, the semiconductor light emitting device 1f according to this modification includes two well layers 14d, but the number of well layers 14d is not limited to two. The number of well layers 14d may be three or more. When the semiconductor light emitting device 1f includes N well layers 14d (N is an integer of 2 or more), the semiconductor light emitting device 1f includes (N-1) intermediate barrier layers from the first intermediate barrier layer to the (N-1)th intermediate barrier layer. The kth intermediate barrier layer (k=1, 2, 3,..., N-1) includes the kth intermediate n-side barrier layer and the kth intermediate p-side barrier layer. If the Al composition ratio and the In composition ratio of the kth intermediate n-side barrier layer of the kth intermediate barrier layer (k=1, 2, 3, . . . , N-1) are ybck and xbck (k=1, 2, 3, . . . , N-1), respectively, and the Al composition ratio and the In composition ratio of the kth intermediate p-side barrier layer are ybk and xbk (k=1, 2, 3, . . . , N-1), respectively, the compositions of the kth intermediate n-side barrier layer and the kth intermediate p-side barrier layer are Al ybck Ga 1-xbck-ybck In xbck As and Al ybk Ga 1-xbk-ybk In xbk As, where ybn1≦ybk≦ybp1, xbn1≦xbk≦xbp1, and ybn1≦ybck≦ybp1 holds, the band gap energy of the kth intermediate n-side barrier layer is equal to or lower than the band gap energy of the kth intermediate p-side barrier layer, and the band gap energy of the kth intermediate p-side barrier layer is equal to or lower than the band gap energy of the p-side barrier layer 14f.

[0170] As a result, the same effects as those of the semiconductor light emitting device 1e according to the fifth modification can be obtained.

[0171] Also, ybp1≦xbp1+0.975ybck+0.069 ybp1≧0.4xbp1+0.975ybck+0.029 0.2≦ybck≦0.4 The following relationship may be satisfied.

[0172] This makes it possible to suppress an increase in the valence band potential energy difference between the kth intermediate n-side barrier layer and the kth intermediate p-side barrier layer, while making the conduction band potential energy of the kth intermediate p-side barrier layer larger than that of the kth intermediate n-side barrier layer. Therefore, it is possible to suppress the overflow of electrons from each well layer 14d without impairing the electrical conductivity of holes between two adjacent well layers 14d.

[0173] Therefore, if ybn1, xbn1, ybp1, xbp1, ybk, and ybck are within the above ranges, the same effects as those of the semiconductor light-emitting element 1e of variant example 5 can be obtained, while by adopting the multiple quantum well structure of this variant example, not only can the operating carrier density in the laser oscillation state in the well layer 14d be reduced, but also electron overflow can be suppressed and the temperature characteristics can be improved.

[0174] [1-9. Variation 7] Next, a semiconductor light emitting device according to Modification 7 of the present embodiment will be described with reference to Fig. 27. Fig. 27 is a cross-sectional view showing the configuration of the light emitting end surface 40 of a semiconductor light emitting device 1g according to this modification. Fig. 27 shows a part of a cross section parallel to the resonance direction of the laser light of the semiconductor light emitting device 1g according to this modification and perpendicular to the main surface of the substrate 10.

[0175] The semiconductor light emitting device 1g according to this modification is different from the semiconductor light emitting device 1 according to the first embodiment in that the light emitting end surface 40 has a so-called end surface window structure, but is the same in other respects. Note that the n-side electrode 31 and the p-side electrode 32 are omitted in FIG. 27. Note that the light emitting end surface 40 is a region including the light emitting end surface 1F of the semiconductor light emitting device 1g. Note that the semiconductor light emitting device 1g may have an end surface window structure not only in the light emitting end surface 40 but also in the rear end surface (i.e., a region including the end surface opposite to the light emitting end surface 1F). The region occupied by the rear end surface is not particularly limited, but may include at least a region whose length in the resonance direction from the rear end surface is 1% of the cavity length, for example.

[0176] Specifically, vacancies or impurities are diffused in the light emitting end surface 40 of the active layer 14 of the semiconductor light emitting device 1g according to this modification. The end surface window structure according to this modification will be described in detail below.

[0177] Among AlAs, GaAs, and InAs, InAs has the largest lattice constant and the smallest band gap energy. When a desired band gap energy is obtained by using an AlGaInAs-based quaternary semiconductor material for the well layer 14d and each barrier layer as in the semiconductor light emitting device 1g of this modification, the In content of the well layer made of AlGaInAs is higher than when a desired band gap energy is obtained by using a semiconductor material made of InGaAs for the well layer, and therefore the compressive strain of the well layer is larger.

[0178] As described above, in a structure in which the well layer 14d and each barrier layer are made of an AlGaInAs-based quaternary semiconductor material, when vacancies or impurities are diffused into the light-emitting end surface 40 of the semiconductor light-emitting device, the strain energy of the well layer 14d is reduced, so that the In atoms in the well layer 14d are easily exchanged with the Al atoms and Ga atoms present at the lattice sites of group III in the stacking direction, and therefore the band gap energy of the well layer 14d is easily increased.

[0179] As a result, the band gap energy of the well layer in the light-emitting end surface portion 40, which has a high light density, becomes large, and a so-called window structure can be formed. In other words, the band gap energy of the portion of the active layer 14 in which the end surface window structure is formed is larger than the band gap energy of the portion of the active layer 14 in which the end surface window structure is not formed. This makes it possible to maintain a state in which the light absorption of the well layer 14d of the light-emitting end surface portion 40 is small even if the band gap energy of the light-emitting end surface portion 40 becomes small due to heat generation. Therefore, it is possible to suppress the occurrence of COD caused by the light absorption of the light-emitting end surface portion 40.

[0180] If the length of the window structure in the resonance direction is Lw, then the longer Lw is, the longer the distance between the cavity end face and the region that does not have the window structure (the gain region). The gain region is the region where light is emitted in the active layer 14. When a current is injected into the gain region, radiative recombination and non-radiative recombination occur in the active layer 14.

[0181] The temperature of the active layer 14 rises not only due to Joule heat in the series resistance component included in the semiconductor light emitting element 1g, but also due to heat generated by non-radiative recombination. The resonator facets are formed by cleavage during the fabrication of the resonator, and therefore are prone to crystal defect levels. When the semiconductor light emitting element 1g generates heat, the band gap energy of the resonator facets becomes even smaller, which further increases light absorption at the crystal defect levels at the resonator facets, making COD more likely to occur.

[0182] If Lw is made longer, the distance between the gain region and the resonator facets increases, and the effect of heat generated by the gain region on the resonator facets is reduced, which is advantageous for suppressing the occurrence of COD. However, if Lw is too long, the length of the gain region becomes shorter, and current concentration in the gain region increases. This increases the overflow of electrons from the active layer 14, degrading the temperature characteristics.

[0183] In contrast, when an AlGaInAs-based quaternary semiconductor material is used for the well layer 14d and each barrier layer as described above, the In atoms in the well layer 14d are easily exchanged with Al atoms and Ga atoms existing at the lattice sites of group III in the stacking direction, which has the effect of making it easier to increase the band gap energy of the well layer 14d. If the band gap energy of the active layer 14 in the window structure region increases, the optical absorption of the laser light in the window structure region decreases, and the heat generation in the window structure region also decreases. For this reason, Variations In the semiconductor light emitting device 1g according to the present invention, even if Lw is shortened, the light emitting diode Fever Effect on the resonator facets Can reduceIn comparison with a conventional structure using InGaAs for the well layer 14d and AlGaAs for each barrier layer, Lw can be made shorter. Specifically, while Lw of 30 μm or more was previously required, when an AlGaInAs-based quaternary semiconductor material is used for the well layer 14d and each barrier layer, COD generation can be suppressed with Lw of 15 μm or more.

[0184] Furthermore, when the window structure is formed by vacancy diffusion, the occurrence of free carrier loss due to the presence of impurities can be suppressed compared to when the window structure is formed by impurity diffusion, and therefore the decrease in slope efficiency can be suppressed.

[0185] (Embodiment 2) A semiconductor light emitting device according to the second embodiment will be described. The semiconductor light emitting device according to the second embodiment includes an active layer 14 and an n-type cladding layer 12 The semiconductor light emitting device according to the present embodiment differs from the semiconductor light emitting device 1 according to embodiment 1 in that an n-side guide layer is further provided between the n-side guide layer and the n-side guide layer. The semiconductor light emitting device according to the present embodiment will be described below with reference to FIG. 28, focusing on the differences from the semiconductor light emitting device 1 according to embodiment 1.

[0186] Fig. 28 is a schematic cross-sectional view showing an overall configuration of a semiconductor light emitting device 101 according to this embodiment. As shown in Fig. 28, the semiconductor light emitting device 101 according to this embodiment includes an n-side guide layer 13, a first strain control layer 15, and a second strain control layer 16 in addition to the respective components of the semiconductor light emitting device 1 according to the first embodiment.

[0187] The n-side guide layer 13 is an n-type semiconductor layer disposed between the n-type cladding layer 12 and the active layer 14. The n-side guide layer 13 has a refractive index larger than that of the n-type cladding layer 12. This allows the light distribution in the vertical direction to be disposed closer to the active layer 14 than in the semiconductor light emitting device 1 according to the first embodiment. This allows the reduction in the light confinement factor in the active layer 14 to be suppressed. In this embodiment, the Al composition ratio of the n-side guide layer 13 is made lower than that of the n-type cladding layer 12, thereby increasing the refractive index of the n-side guide layer 13. In addition, the n-side guide layer 13 contains n-type impurities, and the impurity concentration of the region of the n-side guide layer 13 on the n-type cladding layer 12 side is lower than the impurity concentration of the region on the active layer 14 side. This allows the waveguide loss caused by the impurities in the n-side guide layer 13 to be reduced while suppressing the electrical conductivity of the n-side guide layer 13 from being impaired. Specifically, the n-side guide layer 13 is made of an Al 0.27 Ga 0.73 The n-side guide layer 13 has a thickness of 0.25 μm on the active layer 14 side, and the n-side guide layer 13 has a concentration of 5×10 17 cm -3 The 0.75 μm thick portion on the n-type cladding layer 12 side is doped with Si at a concentration of 5×10 16 cm -3 The impurity concentration of the n-side guide layer 13 is not particularly limited, but in order to reduce the waveguide loss in the n-side guide layer 13, the impurity concentration of the portion of the n-side guide layer 13 on the n-type cladding layer 12 side is set to, for example, 1×10 17 cm -3 In order not to impair the electrical conductivity of the n-side guide layer 13, the impurity concentration of the portion of the n-side guide layer 13 on the active layer 14 side may be, for example, 1×10 17 cm -3 It may be made higher.

[0188] The first strain control layer 15 is disposed between the active layer 14 and the p-type cladding layer 17, and is a semiconductor layer containing Al. In this embodiment, the first strain control layer 15 is an Al 0.70 Ga 0.30 This is the As layer.

[0189] The second strain control layer 16 is disposed between the first strain control layer 15 and the p-type cladding layer 17, and is a semiconductor layer having a lower Al composition ratio and a smaller Young's modulus than the first strain control layer 15. In this embodiment, the second strain control layer 16 is an Al 0.30 Ga 0.70 This is the As layer.

[0190] The impurity concentration of the first strain control layer 15 and the second strain control layer 16 is, for example, 2×10 17 cm -3 That's it, 6 x 10 17 cm -3 In this embodiment, the first strain control layer 15 and the second strain control layer 16 have a concentration of 3×10 17 cm -3 is doped with C.

[0191] The first strain control layer 15 and the second strain control layer 16 are layers for suppressing the influence of mounting strain on the active layer 14 when the semiconductor light emitting device 101 is mounted in a junction-down manner (i.e., when the p-side electrode 32 is connected to the mounting surface). In the semiconductor light emitting device 101 according to this embodiment, when the semiconductor light emitting device 101 is mounted in a junction-down manner, most of the stress caused by the mounting strain is absorbed by the second strain control layer 16 having a small Young's modulus. Therefore, it is possible to suppress the stress caused by the mounting strain from being applied to the active layer 14 disposed at a position farther from the mounting surface than the second strain control layer 16. Therefore, it is possible to stabilize the strain in the active layer 14 to the magnitude of the strain determined in the crystal growth. Accordingly, the controllability of the band structure after mounting the semiconductor light emitting device 101 is improved, and stable high-temperature high-power operation is possible. Therefore, according to this embodiment, a semiconductor laser device having excellent temperature characteristics, high slope efficiency, and suitable for high-temperature high-power operation can be stably realized.

[0192] (Embodiment 3) A semiconductor light emitting device according to embodiment 3 will be described. The semiconductor light emitting device according to this embodiment differs from the semiconductor light emitting device 101 according to embodiment 2 in that the p-type semiconductor layer has a ridge portion. The semiconductor light emitting device according to this embodiment will be described below with reference to FIG. 29, focusing on the differences from the semiconductor light emitting device 101 according to embodiment 2.

[0193] 29 is a schematic cross-sectional view showing the overall configuration of a semiconductor light emitting device 201 according to this embodiment. As shown in FIG. 29, the semiconductor light emitting device according to this embodiment 2 01 comprises a substrate 10, a buffer layer 11, an n-type cladding layer 12, an n-side guide layer 13, an active layer 14, a first strain control layer 15, a second strain control layer 16, a p-type cladding layer 17, a contact layer 218, a current blocking layer 20, an n-side electrode 31, and a p-side electrode 32.

[0194] The contact layer 218 according to the present embodiment has a composition similar to that of the contact layer 18 according to the second embodiment, but differs from the contact layer 18 according to the second embodiment in that it has a ridge portion 218r. Two grooves 218t extending in the resonance direction of the laser light are formed in the upper surface of the contact layer 218 (i.e., the surface on the p-side electrode 32 side), and the ridge portion 218r is formed between the two grooves 218t. In the present embodiment, the current is confined intensively in the ridge portion 218r, and a waveguide is formed along the ridge portion 218r.

[0195] The current blocking layer 20 is an insulating layer for concentrating the current on the ridge portion 218r. The current blocking layer 20 is disposed on the contact layer 218 in a region other than the ridge portion 218r. In this embodiment, the current blocking layer 20 is disposed on the contact layer 218 in a region other than the upper surface of the ridge portion 218r. In other words, the current blocking layer 20 has a slit formed on the ridge portion 218r, the slit extending in the resonance direction of the laser light. The current blocking layer 20 is not particularly limited as long as it is an insulating film, but in this embodiment, it is a SiO2 film with a film thickness of 0.02 μm.

[0196] Next, the action and effect of the semiconductor light emitting device 201 according to the present embodiment will be described with reference to Figs. 30 to 32. Fig. 30 is a schematic cross-sectional view showing the dimensions of each part of the semiconductor light emitting device 201 according to the present embodiment. Fig. 31 is a schematic cross-sectional view showing the mounted state of the semiconductor light emitting device 201 according to the present embodiment. Fig. 32 is a graph showing the distribution of shear stress σxy with respect to the position in the x-axis direction of the active layer 14 of the semiconductor light emitting device 201 according to the present embodiment.

[0197] As shown in Fig. 30, the stacking direction of each layer of the semiconductor light emitting element 201 (i.e., the direction perpendicular to the main surface of the substrate 10) is defined as the y-axis direction. The direction perpendicular to the resonance direction of the laser light and the y-axis direction is defined as the x-axis direction. As shown in Fig. 30, the width of each of the two grooves 218t in the x-axis direction is defined as d1, and the width of the ridge portion 218r in the x-axis direction is defined as Wr. The width of the semiconductor light emitting element 201 in the x-axis direction is defined as Wc.

[0198] The stress applied to such a semiconductor light emitting device 201 when the device is mounted junction-down on a submount 202 as shown in FIG. 31 will be described.

[0199] The submount 202 is a plate-like member made of, for example, Cu.

[0200] Here, the thermal expansion coefficient of the semiconductor light emitting element 201 is the thermal expansion coefficient of GaAs (5.35×10 -6 K -1 ), and the thermal expansion coefficient of the submount 202 ( 16.8 ×10 -6 K -1) is smaller than the above. When the semiconductor light emitting element 201 is junction-down mounted on such a submount 202, a shear stress according to the difference in thermal expansion coefficient between the semiconductor light emitting element 201 and the submount 202 is applied to the active layer 14 of the semiconductor light emitting element 201. In this case, the semiconductor light emitting element 201 receives a stress from the submount 202 in a direction that causes it to shrink in the x-axis direction. Specifically, as shown in FIG. 31, a clockwise shear stress σ1R and a counterclockwise shear stress σ1L are applied to the right and left ends of the semiconductor light emitting element 201 in the x-axis direction, respectively. In addition, a counterclockwise shear stress σ2R and a clockwise shear stress σ2L are applied to the right and left ends of the ridge portion 218r, respectively. In this way, a shear stress symmetrical with respect to the center of the ridge portion 218r in the x-axis direction is applied to the semiconductor light emitting element 201.

[0201] Here, the shear stress applied to the semiconductor light emitting element 201 will be described with reference to Fig. 31 and Fig. 32. Fig. 32 shows the distribution of shear stress in the x-axis direction when the width Wc of the semiconductor light emitting element 201 in the x-axis direction is 500 µm and the width Wr of the ridge portion 218r in the x-axis direction is 200 µm. Fig. 32 also shows the calculation results when the width d1 of the groove 218t is 20 µm, 40 µm, and 80 µm. Fig. 32 also shows the calculation results of the shear stress when the groove 218t is not present.

[0202] 31, for example, at the right end in the x-axis direction of the ridge portion 218r, the shear stress σ2R caused by the groove 218t and the shear stress σ1R caused by the right end in the x-axis direction of the semiconductor light emitting element 201 are in opposite directions, so the shear stress is weaker (see the point where position x is 100 μm in FIG. 32). The shear stress is also weaker at the left end in the x-axis direction of the ridge portion 218r, similar to the right end (see the point where position x is −100 μm in FIG. 32).

[0203] In the semiconductor light emitting device 201, as shown by the thick dashed arrow in FIG. 30, the current reaches the active layer 14 while spreading from the ridge portion 218r in the x-axis direction. For this reason, the laser light in the semiconductor light emitting device 201 is distributed in the active layer 14 up to the region corresponding to the position of the groove 218t in the x-axis direction, and is therefore affected by the shear stress of the groove 218t. The dashed ellipse shown in FIG. 30 indicates the outer edge of the distribution region of the laser light. Furthermore, if the distribution of the shear stress in the active layer 14 is not completely antisymmetric with respect to the center in the x-axis direction of the ridge portion 218r, when the shear stress causes birefringence in the semiconductor light emitting device 201, the correlation integral between the light distribution and the shear stress will not be 0, and the polarization plane will be tilted. Here, the correlation integral between the shear stress and the light distribution is expressed by the following formula.

[0204]

number

[0205] In this embodiment, the groove 218t is formed to reduce the shear stress at the end of the ridge portion 218r in the x-axis direction, and therefore the influence on the light distribution caused by the shear stress can be suppressed. Therefore, in the semiconductor light emitting device 201 according to this embodiment, when an asymmetric distortion occurs in the semiconductor light emitting device 201 with respect to the center in the x-axis direction, the polarization plane is tilted, and the polarization ratio is prevented from decreasing. For example, the width d1 of the groove 218t in the x-axis direction is set to 10 μm or more to weaken the shear stress near the end of the ridge portion 218r in the x-axis direction. On the other hand, if the width d1 of the groove 218t is too wide, the load is concentrated on the ridge portion 218r during junction-down mounting, so the width d1 of the groove 218t may be set to 40 μm or less.

[0206] Regarding the depth of the groove 218t, if the step portion of the groove 218t (i.e., the portion where the bottom surface and the side surface of the groove 218t are connected) is placed too close to the active layer 14, the shear stress generated in the active layer 14 increases due to the influence of the unevenness, and the polarization ratio decreases. For this reason, the depth of the groove 218t may be 0.3 μm or less. In this embodiment, the groove 218t is formed only in the contact layer 218, and its depth is 0.2 μm.

[0207] (Embodiment 4) A semiconductor light emitting device according to embodiment 4 and a manufacturing method thereof will be described. The semiconductor light emitting device according to this embodiment differs from the semiconductor light emitting device 1c according to modification 3 of embodiment 1 mainly in the materials used for the p-side guide layer, the n-type cladding layer, and the p-type cladding layer. The semiconductor light emitting device according to this embodiment will be described below, focusing on the differences from the semiconductor light emitting device 1c according to modification 3 of embodiment 1.

[0208] [4-1. Overall composition] First, the overall configuration of the semiconductor light emitting device according to this embodiment will be described. The semiconductor light emitting device according to this embodiment includes a substrate, an n-type cladding layer, an active layer, a p-type cladding layer, a current confinement layer, a contact layer, an n-side electrode, and a p-side electrode, similar to the semiconductor light emitting device 1c according to the third modification of the first embodiment. The semiconductor light emitting device according to this embodiment further includes an n-side guide layer disposed between the n-type cladding layer and the active layer.

[0209] The semiconductor light emitting device according to this embodiment differs from the semiconductor light emitting device 1c mainly in the materials used in each layer. Hereinafter, among the layers included in the semiconductor light emitting device according to this embodiment, layers using materials different from those of the layers included in the semiconductor light emitting device 1c and the n-side guide layer will be described.

[0210] The composition of the n-type cladding layer is as follows: (Al yn2 Ga 1-yn2 ) 0.5 In 0.5 It is represented by P. Note that (Al yn2 Ga 1-yn2) 0.5 In 0.5 The composition ratio of In in the description of P (and (Al yn2 Ga 1-yn2 The composition ratio of (Al) is a range of composition ratios that is rounded to 0.5 after rounding to the first decimal place. Similarly, other composition ratios expressed as decimals are not limited to a single value, but are a range of composition ratios that is rounded to the nearest decimal place. The composition of the n-type cladding layer is (Al yn2 Ga 1-yn2 ) 0.5 In 0.5 By using P, vacancies or impurities such as Zn and Mg are easily diffused in the n-type cladding layer. Therefore, when forming an end face window structure by diffusing vacancies or impurities in the semiconductor light emitting element, the time required for formation can be reduced. In addition, since the concentration of the impurities used when diffusing the impurities can be reduced, light absorption by the impurities can be reduced. Therefore, a decrease in the luminous efficiency of the semiconductor light emitting element can be suppressed.

[0211] In order to make the distortion of the n-type cladding layer formed on the substrate made of n-type GaAs ±0.2% or less, when the Al composition ratio is 0 to 0.6, the In composition ratio may be 0.45 to 0.513. In this embodiment, the n-type cladding layer is a 3.5 μm-thick n-type (Al 0.14 Ga 0.86 ) 0.5 In 0.5 The n-type cladding layer is a P layer. The n-type cladding layer includes multiple parts doped with impurities of different concentrations. The n-type cladding layer is doped with impurities of different concentrations from each other, starting from the end face closest to the substrate. 18 cm -3 A 2.5 μm thick section doped with Si at a concentration of 5×10 17 cm -3 The 0.5 μm thick section is doped with Si of 2×10 17 cm -3 The Si doped portion is 0.5 μm thick.

[0212] The n-side guide layer is disposed between the n-type cladding layer and the active layer. In this embodiment, the n-side guide layer is an n-type (Al 0.04 Ga 0.96 ) 0.5 In 0.5 The n-side guide layer is a 1×10 17 cm -3 The Si is doped.

[0213] The active layer includes an n-side first barrier layer, an n-side second barrier layer, a well layer, a p-side barrier layer, and a p-side guide layer. In this embodiment, the n-side first barrier layer is an undoped Al 1110 ... 0.5 Ga 0.5 The n-side second barrier layer is an undoped Al layer with a thickness of 3.5 nm. 0.55 Ga 0.45 The well layer is an undoped In layer with a thickness of 6 nm. 0.08 Ga 0.92 The p-side barrier layer is an undoped Al layer with a thickness of 3.5 nm. 0.59 Ga 0.16 In 0.25 This is the As layer.

[0214] The composition of the p-side guide layer is (Al ygp2 Ga 1-gp2 ) 0.5 In 0.5 The composition of the p-side guide layer is expressed as (Al ygp2 Ga 1-gp2 ) 0.5 In 0.5 By using P, impurities such as vacancies or Zn, Mg, etc., can be easily diffused in the p-side guide layer. Therefore, the same effect as that of the n-type cladding layer described above can be achieved. In this embodiment, a p-type (Al 0.04 Ga 0.96 ) 0.5 In 0.5 The p-side guide layer has a concentration of 1×10 17 cm -3 is doped with C.

[0215] The composition of the p-type clad layer is expressed as (Al yp2 Ga 1-yp2 ) 0.5 In 0.5 P, where the composition ratio of Al is yp2. By setting the composition of the p-type clad layer to (Al yp2 Ga 1-yp2 ) 0.5 In 0.5 P, holes or impurities such as Zn and Mg diffuse easily in the p-type clad layer. Therefore, the same effect as that of the above-described n-type clad layer is achieved. In this embodiment, the p-type clad layer is a p-type (Al 0.6 Ga 0.4 ) 0.5 In 0.5 P layer with a thickness of 0.8 μm. The p-type clad layer is doped with C at a concentration of 2×10 18 cm -3 .

[0216] Furthermore, in this embodiment, regarding the composition ratio yn2 of Al in the n-type clad layer and the composition ratio yp2 of Al in the p-type clad layer, the relationship 0 < yn2 < yp2 < 1 holds. Thereby, the refractive index of the p-type clad layer can be reduced compared to that of the n-type clad layer. Therefore, the intensity distribution of the laser light can be biased toward the n-type clad layer side. That is, since the laser light propagating through the p-type clad layer can be reduced, the free carrier loss caused by the impurities in the p-type clad layer can be reduced. As a result, the waveguide can be made to have low loss.

[0217] [4-2. Manufacturing method] Next, the manufacturing method of the semiconductor light-emitting device according to this embodiment will be described with reference to FIG. 33. FIG. 33 is a flowchart showing the steps of the manufacturing method of the semiconductor light-emitting device according to this embodiment.

[0218] As shown in FIG. 33, first, a substrate is prepared (S10). In this embodiment, an n-type GaAs substrate is prepared.

[0219] Subsequently, an n-type clad layer is formed above the substrate (S20). In this embodiment, on the upper surface of the substrate, as the n-type clad layer, an n-type (Alyn2 Ga 1-yn2 ) 0.5 In 0.5 Forms the P layer.

[0220] Next, an n-side guide layer is formed on the upper side of the n-type cladding layer (S30). In this embodiment, an n-type (Al 0.04 Ga 0.96 ) 0.5 In 0.5 Forms the P layer.

[0221] Next, an active layer is formed above the n-side guide layer (S40). In this embodiment, the active layer is formed by forming an n-side first barrier layer, an n-side second barrier layer, a well layer, a p-side barrier layer, and a p-side guide layer in this order on the upper surface of the n-side guide layer. Specifically, the n-side first barrier layer is made of undoped Al. 0.5 Ga 0.5 An As layer was formed, and an undoped Al layer was used as the n-side second barrier layer. 0.55 Ga 0.45 An As layer was formed, and undoped In was used as the well layer. 0.08 Ga 0.92 An As layer was formed, and an undoped Al layer was used as the p-side barrier layer. 0.59 Ga 0.16 In 0.25 An As layer is formed and a p-type (Al ygp2 Ga 1-gp2 ) 0.5 In 0.5 Forms the P layer.

[0222] Next, a p-type cladding layer is formed on the active layer (S50). In this embodiment, a p-type (Al yp2 Ga 1-yp2 ) 0.5 In 0.5 Forms the P layer.

[0223] Next, a current confinement layer is formed above the p-type cladding layer (S60). In this embodiment, an n-type GaAs layer is formed as a current confinement layer on the upper surface of the p-type cladding layer, and a long opening is formed along the laser resonance direction by photolithography, etching, or the like.

[0224] Next, a contact layer is formed above the current confinement layer (S70). In this embodiment, a p-type GaAs layer is formed as the contact layer on the top surface of the current confinement layer and in the opening.

[0225] Each of the semiconductor layers is formed by, for example, metal-organic chemical vapor deposition (MOCVD).

[0226] Next, an end face window structure is formed in the active layer (S80). Specifically, vacancies or impurities are diffused from the upper surface of the contact layer into the light-emitting end face of the active layer. By diffusing the vacancies or impurities in this manner, the quantum well structure in the light-emitting end face of the active layer can be disordered. As a result, the band gap energy of the active layer can be increased. In other words, a window structure can be formed. In this embodiment, an n-type (Al yn2 Ga 1-yn2 ) 0.5 In 0.5 The P layer is a p-type (Al ygp2 Ga 1-gp2 ) 0.5 In 0.5 The P layer is a p-type cladding layer. yp2 Ga 1-yp2 ) 0.5 In 0.5 Since the P layer is formed, vacancies or impurities are easily diffused. Therefore, the time required for forming the end face window structure can be reduced. In addition, since the concentration of the impurities used when diffusing the impurities can be reduced, light absorption by the impurities can be reduced. Therefore, a decrease in the light emission efficiency of the semiconductor light emitting device can be suppressed. The end face window structure may be formed not only on the light emitting end face portion, but also on both end faces forming the resonator of the semiconductor light emitting device.

[0227] Next, electrodes are formed (S90). Specifically, a p-side electrode is formed on the upper surface of the contact layer, and an n-side electrode is formed on the lower main surface of the substrate. In this embodiment, a Ti film, a Pt film, and an Au film are formed in this order from the contact layer side as the p-side electrode, and an AuGe film, a Ni film, an Au film, a Ti film, a Pt film, a Ti film, a Pt film, and an Au film are formed in this order from the substrate 10 side as the n-side electrode.

[0228] In this manner, the semiconductor light emitting device according to the present embodiment can be manufactured.

[0229] (Variations, etc.) Although the semiconductor light emitting device and the manufacturing method thereof according to the present disclosure have been described based on the respective embodiments, the present disclosure is not limited to the above-described respective embodiments.

[0230] For example, in each of the above-described embodiments, the semiconductor light emitting element is a semiconductor laser element, but 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.

[0231] In addition, in each of the above embodiments, an AlGaInAs-based material is used in the semiconductor light-emitting element, but other semiconductor materials may be used. For example, a nitride-based semiconductor material may be used. Specifically, an AlGaInN-based material may be used. Hereinafter, the conduction band potential energy and the valence band potential energy of the AlGaInAs-based material and the AlGaInN-based material will be described.

[0232] The physical properties that affect the conduction band potential energy and the valence band potential energy are electron affinity, band gap energy, and lattice distortion. The lattice distortion is determined by the lattice constant of the semiconductor layer and the lattice constant of the substrate on which the semiconductor layer is laminated. In the binary compounds (AlAs, GaAs, and InAs, as well as AlN, GaN, and InN) that are the components of the AlGaInAs-based material and the AlGaInN-based material, the magnitude relationship of the electron affinity, band gap energy, and lattice constant is as follows. The electron affinity is smaller in the order of InAs, GaAs, and AlAs, and smaller in the order of InN, GaN, and AlN. The band gap energy is smaller in the order of AlAs, GaAs, and InAs, and smaller in the order of AlN, GaN, and InN. The lattice constants of the components of the AlGaInAs-based material are larger for InAs than for GaAs and AlAs, and are approximately the same for GaAs and AlAs. In addition, the lattice constants of the components of the AlGaInN-based materials are larger in InN than in GaN and AlN, but are comparable between GaN and AlN.

[0233] From the above relationship, it can be seen that even if the group V atoms of the quaternary semiconductor materials are different, the magnitude relationship of the above physical properties is similar.

[0234] Among the components of AlGaInAs-based materials, AlAs, GaAs, and InAs, InAs has the largest lattice constant and the smallest band gap energy. When a desired band gap energy is obtained by using layers containing an AlGaInAs-based quaternary semiconductor material for the well layer and barrier layer, the In content of the well layer made of AlGaInAs is higher than when a desired band gap is obtained by using a layer made of InGaAs for the well layer. Pressure The shrinkage distortion becomes large.

[0235] Among AlGaInN-based materials, InN has the largest lattice constant and the smallest band gap energy among AlN, GaN, and InN. When a desired band gap energy is obtained by using layers containing an AlGaInN-based quaternary semiconductor material for the well layer and barrier layer, the In content of the well layer made of AlGaInN is higher, resulting in a larger compressive strain in the well layer, compared to when the desired band gap is obtained by using an InGaN well layer or an AlGaN barrier layer.

[0236] Moreover, the relationship that the electron affinity increases as the In content increases and decreases as the Al content increases applies to both AlGaInAs-based materials and AlGaInN-based materials.

[0237] For this reason, when an AlGaInAs-based material is used for the barrier layer and the band gap energy is increased while increasing the In composition ratio, the change in conduction band potential energy (ΔEbc) becomes larger than the change in valence band potential energy (ΔEbv), which is also the case with AlGaInN-based materials. Therefore, an AlGaInN-based quaternary semiconductor material may be used as a material for forming the semiconductor light emitting device according to each of the above embodiments. For example, the semiconductor light emitting device 1a according to the first modification of the first embodiment is formed of a GaN substrate, an Al 0.25 Ga 0.75 N(Si concentration: 1×10 18 cm -3 ) and an n-type cladding layer of 30 nm thick Al 0.2 Ga 0.8 The n-side first barrier layer is made of N and the thickness is 2.8 nm. 0.01 Ga 0.98 In 0.01 A well layer made of N and a 7-nm-thick Al 0.40 Ga 0.515 In 0.085 The p-side barrier layer is made of N and the thickness is 30 nm. 0.2 Ga 0.8 The p-side guide layer is made of N and has a thickness of 0.6 μm. 0.3 Ga 0.7 N(Mg concentration: 1×10 19 cm-3 ) may be provided as a p-type cladding layer. This makes it possible to obtain an ultraviolet laser beam having an oscillation wavelength in the 360 ​​nm band, and to realize a nitride-based semiconductor light-emitting device that can suppress the overflow of electrons from the well layer while suppressing the operating voltage.

[0238] Furthermore, when at least one of the p-side intermediate layer 14e, the p-side barrier layer 14f, and the p-side guide layer 14g is doped with a p-type impurity, the conduction band potential energy of this layer is increased. This enhances the effect of suppressing the overflow of electrons during high-temperature, high-power operation. Furthermore, in this case, the electrical resistance of the layer doped with the p-type impurity is reduced, so that the series resistance component contained in the semiconductor light-emitting device can be reduced. As a result, the generation of Joule heat during operation can also be suppressed, so that the thermally saturated optical output during high-temperature operation of the semiconductor light-emitting device can be further increased. As the p-type impurity, C (carbon atom) or Mg, which is unlikely to diffuse from the doped position, may be used.

[0239] Here, the doping concentration is set to 1×10 in the case of AlGaInAs-based materials containing AlGaAs in order to increase the electrical conductivity and the conduction band potential energy. 17 cm -3 It may be more than 2 x 10 17 cm -3 Moreover, if the doping concentration of the impurity in the p-side intermediate layer 14e, the p-side barrier layer 14f, and the p-side guide layer 14g near the well layer 14d is too high, the free carrier loss increases, leading to a decrease in the light emission efficiency of the semiconductor light emitting device. 18 cm -3 It may be less than or equal to 6 x 10 17 cm -3 It may be the following.

[0240] In the case of AlGaInN-based materials including AlGaN, when Mg is used as a dopant, the doping concentration is set to 1×1018 cm -3 It may be more than 2 x 10 18 cm -3 Moreover, if the doping concentration of the impurity in the p-side intermediate layer 14e, the p-side barrier layer 14f, and the p-side guide layer 14g near the well layer 14d is too high, the free carrier loss increases, leading to a decrease in the light emission efficiency of the semiconductor light emitting device. 19 cm -3 It may be less than or equal to 6 x 10 18 cm -3 It may be the following.

[0241] In addition, when doping at least one of the p-side intermediate layer 14e, the p-side barrier layer 14f, and the p-side guide layer 14g, the p-type impurity doping concentration may be relatively low on the side closer to the well layer 14d. In this way, the impurity concentration of the impurity doped region closest to the well layer 14d, which is the light-emitting layer, is reduced, so that it is possible to reduce free carrier loss. Therefore, it is possible to reduce the waveguide loss of the laser light propagating through the waveguide.

[0242] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments that a person skilled in the art may conceive, and forms realized by arbitrarily combining the components and functions of the above-described embodiments within the scope that does not deviate from the spirit of the present disclosure.

[0243] For example, each of the modified examples according to the first embodiment may be combined with each other, or may be combined with other embodiments. For example, the end face window structure according to the seventh modified example of the first embodiment may be applied to other modified examples of the first embodiment and other embodiments. In addition, when a nitride-based semiconductor material is used, InN has the largest lattice constant and the smallest band gap energy among AlN, GaN, and InN. In this case, when a desired band gap energy is obtained by using a layer containing a quaternary semiconductor material made of AlGaInN for the well layer and each barrier layer, the In content of the well layer made of AlGaInN is increased, and the compressive strain of the well layer is increased, compared with the case where a desired band gap energy is obtained by using InGaN or AlGaN for the well layer. Therefore, a window structure can be easily formed in the same manner as when a layer containing an AlGaInAs-based material is used for the well layer and each barrier layer described above.

[0244] The method for manufacturing a semiconductor light-emitting device according to the fourth embodiment can also be applied to the manufacture of semiconductor light-emitting devices according to other embodiments and modifications. For example, a manufacturing method in which the n-side guide layer forming step of the manufacturing method for a semiconductor light-emitting device according to the fourth embodiment is omitted and the configuration of each semiconductor layer is changed can be applied to the manufacture of a semiconductor light-emitting device according to the first embodiment and each modification thereof. A manufacturing method in which the first strain control layer 15 and the second strain control layer 16 are formed in the manufacturing method for a semiconductor light-emitting device according to the fourth embodiment and the configuration of each semiconductor layer is changed can be applied to the manufacture of a semiconductor light-emitting device 101 according to the second embodiment. A manufacturing method in which the current constriction layer forming step is omitted in the p-type cladding layer forming step of the manufacturing method for a semiconductor light-emitting device according to the fourth embodiment and the configuration of each semiconductor layer is changed can be applied to the manufacture of a semiconductor light-emitting device 201 according to the third embodiment. [Industrial Applicability]

[0245] The semiconductor light emitting element of the present disclosure can be used, for example, as a high-output, highly efficient light source for laser processing. [Explanation of symbols]

[0246] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 101, 201 Semiconductor light emitting device 10 Substrate 11 Buffer layer 12 n-type cladding layer 13 n-side guide layer 14 Active layer 14a N-side first barrier layer 14b N-side second barrier layer 14c n-side third barrier layer 14d Well layer 14e p side middle layer 14f p-side barrier layer 14g p-side guide layer 14h, 14ha First intermediate barrier layer 14i First intermediate n-side barrier layer 14j First intermediate p-side barrier layer 15 First Distortion Control Layer 16 Second strain control layer 17 p-type cladding layer 18, 218 Contact layer 19 Current confinement layer 19a opening 20 Current Blocking Layer 31 n-side electrode 32 p side electrode 40 Light output end face 202 Submount 218r Ridge 218t groove

Claims

1. A substrate; an n-type cladding layer disposed above the substrate; an active layer disposed above the n-type cladding layer; a p-type cladding layer disposed above the active layer; The active layer is A well layer; an n-side first barrier layer disposed on the n-type cladding layer side of the well layer and made of a quaternary semiconductor material containing Al, Ga, and In and a group V atom; a p-side barrier layer disposed on the p-type cladding layer side of the well layer and made of a quaternary semiconductor material containing Al, Ga, and In and the group V atom; the p-side barrier layer contains In, the In composition ratio of the n-side first barrier layer is lower than the In composition ratio of the p-side barrier layer, The band gap energy of the n-side first barrier layer is smaller than the band gap energy of the p-side barrier layer. Semiconductor light emitting element.

2. A substrate, an n-type cladding layer disposed above the substrate; an active layer disposed above the n-type cladding layer; a p-type cladding layer disposed above the active layer; The active layer is A well layer; an n-side first barrier layer disposed on the n-type cladding layer side of the well layer; a p-side barrier layer disposed on the p-type cladding layer side of the well layer, the p-side barrier layer contains In, the In composition ratio of the n-side first barrier layer is lower than the In composition ratio of the p-side barrier layer, the band gap energy of the n-side first barrier layer is smaller than the band gap energy of the p-side barrier layer; The composition of the n-side first barrier layer is Al ｙｂｎ１ G １－ｘｂｎ１－ｙｂｎ１ In ｘｂｎ１ As is represented by The composition of the p-side barrier layer is Al ｙｂｐ１ G １－ｘｂｐ１－ｙｂｐ１ In ｘｂｐ１ As is represented by The relationships 0≦ybn1≦1, 0≦xbn1<1, 0<ybp1<1, 0<xbp1<1, and xbn1<xbp1 are satisfied. Semiconductor light emitting element.

3. Furthermore, the relationship ybn1<ybp1 holds. The semiconductor light emitting device according to claim 2 .

4. moreover, 0.2≦ybn1≦0.4 ybp1≦xbp1+0.975ybn1+0.069, ybp1≧0.4xbp1+0.975ybn1+0.029, and xbp1≦0.15 The relationship is The semiconductor light-emitting device according to claim 2 .

5. a p-side intermediate layer disposed between the well layer and the p-side barrier layer; The composition of the p-side intermediate layer is Al ｙｋｐ１ G １－ｙｋｐ１ As is represented by ybp1≦xbp1+0.975ykp1+0.069, ybp1≧0.4xbp1+0.975ykp1+0.029, and 0.2≦ykp1≦0.4 The relationship is The semiconductor light emitting device according to any one of claims 2 to 4.

6. an n-side second barrier layer disposed between the n-side first barrier layer and the well layer; The composition of the n-side second barrier layer is Al ｙｂｎ２ G １－ｘｂｎ２－ｙｂｎ２ In ｘｂｎ２ As is represented by ybn2≧xbn2+ybn1, ybn2≦0.4xbn2+0.975ybn1+0.061, xbn2≦0.15, and 0.2≦ybn1≦0.35 The relationship is The semiconductor light emitting device according to any one of claims 2 to 5.

7. an n-side third barrier layer disposed between the well layer and the n-side second barrier layer; The composition of the n-side third barrier layer is Al ｙｂｎ３ G １－ｙｂｎ３ As is represented by ybn2≧xbn2+ybn3, ybn2≦0.4xbn2+0.975ybn3+0.061, and 0.2≦ybn3≦0.35 The relationship is The semiconductor light emitting device according to claim 6 .

8. a p-side guide layer disposed between the p-side barrier layer and the p-type cladding layer, the p-side guide layer having a refractive index greater than that of the p-type cladding layer; The semiconductor light emitting device according to any one of claims 2 to 7.

9. The composition of the p-side guide layer is Al ｙｇｐ１ G １－ｙｇｐ１ As is represented by ybp1≦xbp1+0.975ygp1+0.069, ybp1≧0.4xbp1+0.975ygp1+0.029, and 0.2≦ygp1≦0.4 The relationship is The semiconductor light emitting device according to claim 8 .

10. The p-side guide layer is (Al ｙｇｐ２ G １－ｙｇｐ２ ) ０．５ In ０．５ Represented by P The semiconductor light emitting device according to claim 8 .

11. The composition of the n-type cladding layer is Al ｙｎ１ G １－ｙｎ１ As is represented by The composition of the p-type cladding layer is Al ｙｐ１ G １－ｙｐ１ As is represented by The relationship 0<yn1<yp1<1 holds. The semiconductor light emitting device according to any one of claims 1 to 10.

12. The composition of the n-type cladding layer is (Al ｙｎ２ G １－ｙｎ２ ) ０．５ In ０．５ It is represented by P, The composition of the p-type cladding layer is (Al ｙｐ２ G １－ｙｐ２ ) ０．５ In ０．５ It is represented by P, The relationship 0<yn2<yp2<1 holds. The semiconductor light emitting device according to any one of claims 1 to 10.

13. The composition of the well layer is Al ｙｗ G １－ｘｗ－ｙｗ In ｘｗ As is represented by The relationship 0≦yw<1 and 0<xw<1 is satisfied. The semiconductor light emitting device according to any one of claims 1 to 12.

14. Furthermore, the relationship 0<yw<1 holds true. The semiconductor light emitting device according to claim 13 .

15. The substrate is a GaAs substrate. The semiconductor light emitting device according to any one of claims 1 to 14.

16. The n-side first barrier layer and the p-side barrier layer are made of an AlGaInN-based material. The semiconductor light emitting device according to claim 1 .

17. The n-type cladding layer, the active layer, and the p-type cladding layer are made of a nitride-based semiconductor material. The semiconductor light emitting device according to claim 16 .

18. The n-side first barrier layer has an Al composition ratio lower than an Al composition ratio of the p-side barrier layer. The semiconductor light emitting device according to claim 1 or 16.

19. The band gap energy of the n-type cladding layer is smaller than the band gap energy of the p-type cladding layer. The semiconductor light emitting device according to any one of claims 1 to 18.

20. An end surface window structure is formed on the light emitting end surface of the active layer. The semiconductor light emitting device according to any one of claims 1 to 19.

21. The band gap energy of a portion of the active layer in which the end face window structure is formed is larger than the band gap energy of a portion of the active layer in which the end face window structure is not formed. The semiconductor light emitting device according to claim 20 .

22. A method for manufacturing a semiconductor light emitting device, comprising the steps of: providing a substrate; forming an n-type cladding layer over the substrate; forming an active layer above the n-type cladding layer; forming a p-type cladding layer above the active layer; forming an end face window structure in the active layer; The active layer is A well layer; an n-side first barrier layer disposed on the n-type cladding layer side of the well layer and made of a quaternary semiconductor material containing Al, Ga, and In and a group V atom; a p-side barrier layer disposed on the p-type cladding layer side of the well layer and made of a quaternary semiconductor material containing Al, Ga, and In and the group V atom; the p-side barrier layer contains In, the In composition ratio of the n-side first barrier layer is lower than the In composition ratio of the p-side barrier layer, the band gap energy of the n-side first barrier layer is smaller than the band gap energy of the p-side barrier layer; In the step of forming the end face window structure, vacancies or impurities are diffused into the active layer. A method for manufacturing a semiconductor light emitting device.

23. A method for manufacturing a semiconductor light emitting device, comprising the steps of: providing a substrate; forming an n-type cladding layer over the substrate; forming an active layer above the n-type cladding layer; forming a p-type cladding layer above the active layer; forming an end face window structure in the active layer; The active layer is A well layer; an n-side first barrier layer disposed on the n-type cladding layer side of the well layer; a p-side barrier layer disposed on the p-type cladding layer side of the well layer, the p-side barrier layer contains In, the In composition ratio of the n-side first barrier layer is lower than the In composition ratio of the p-side barrier layer, the band gap energy of the n-side first barrier layer is smaller than the band gap energy of the p-side barrier layer; The composition of the n-side first barrier layer is represented by Al ybn1 Ga 1-xbn1-ybn1 In xbn1 As, The composition of the p-side barrier layer is expressed as Al ybp1 Ga 1-xbp1-ybp1 In xbp1 As, The relationships 0≦ybn1≦1, 0≦xbn1<1, 0<ybp1<1, 0<xbp1<1, and xbn1<xbp1 are satisfied, In the step of forming the end face window structure, vacancies or impurities are diffused into the active layer. A method for manufacturing a semiconductor light emitting device.

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