Semiconductor light emitting element and method for manufacturing semiconductor light emitting element

Abstract

A semiconductor light emitting element (1) includes a substrate (10), an n-type clad layer (12) disposed above the substrate (10), an active layer (14) disposed above the n-type clad layer (12), and a p-type clad layer (17) disposed above the active layer (14); 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) side 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 band gap energy of the n-side first barrier layer (14a) is smaller than the band gap energy of the p-side barrier layer (14f).

Description

TECHNICAL FIELD

[0001] The present application relates to a semiconductor light emitting element, and particularly to a semiconductor light emitting element provided with an active layer having a quantum well structure. BACKGROUND

[0002] Conventionally, lasers have been used for processing applications, and a laser source with high output and high efficiency is required. A semiconductor light emitting element such as a semiconductor laser element is used as such a laser source. In processing applications, particularly in welding processing applications, further high output of the laser source is desired.

[0003] One example of a technique for high output of a semiconductor light emitting element is described in Patent Literature 1. In Patent Literature 1, a technique is described in which, in an active layer having a quantum well structure, an energy difference δEv between a first quantum energy level of a heavy hole in a well layer and an energy level at the top of a valence band of a barrier layer is made small, and an energy difference δEc between a first quantum energy level of an electron in the well layer and an energy level at the bottom of a conduction band of the barrier layer is made large. In the semiconductor light emitting element described in Patent Literature 1, by making the energy difference δEv small, the hole is made to move easily, thereby increasing the probability of recombination of the hole and the electron, and by making the energy difference δEc large, overflow (i.e., leakage) of the electron from the well layer is suppressed.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 10-256659 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the semiconductor light emitting element described in Patent Literature 1, since the energy difference δEc is large, the operating voltage required for injection of the electron into the well layer increases. Consequently, the self-heating of the semiconductor light emitting element increases, and the thermal saturation level decreases.

[0009] The present application is made to solve such a problem, and aims to provide a semiconductor light emitting element or the like capable of suppressing overflow of the electron from the well layer while suppressing the operating voltage.

[0010] MEANS FOR SOLVING THE PROBLEM

[0011] In order to solve the above problems, one technical solution of the semiconductor light-emitting device of the present invention 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 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; 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 bandgap energy of the n-side first barrier layer is smaller than the bandgap energy of the p-side barrier layer.

[0012] 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 bandgap of the n-side first barrier layer is made smaller than that of the p-side barrier layer. Thereby, the energy difference ΔEc between the conduction band potentials of the p-side barrier layer and the n-side first barrier layer can be made larger than the energy difference ΔEv between the valence band potentials of the p-side barrier layer and the n-side first barrier layer. Therefore, an increase in the voltage required for hole conduction, that is, an increase in the operating voltage of the semiconductor light-emitting device, can be suppressed, and the overflow of electrons from the well layer can be suppressed.

[0013] In addition, in one technical solution of the semiconductor light-emitting device of the present invention, it may be that 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 represented by Al ybp1 Ga 1-xbp1-ybp1 [[ID=十六]]In [[ID=十七]] xbp1 As; the relationships of 0≦ybn1≦1, 0≦xbn1<1, 0<ybp1<1, 0<xbp1<1, and xbn1<xbp1 hold.

[0014] By adopting 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 that of the p-side barrier layer, and the bandgap of the n-side first barrier layer can be made smaller than that of the p-side barrier layer.

[0015] In addition, in one technical solution of the semiconductor light-emitting device of the present invention, it may be that further, the relationship of ybn1<ybp1 holds.

[0016] Thereby, the energy difference ΔEc between the conduction band potentials of the p-side barrier layer and the n-side first barrier layer increases, so the overflow of electrons from the well layer can be further suppressed.

[0017] Further, in the technical solution of the semiconductor light emitting element of the present application, it can be that further, 0.2≦ybn1≦0.4, ybp1≦xbp1+0.975ybn1+0.069, ybp1≧0.4xbp1+0.975ybn1+0.029, and xbp1≦0.15.

[0018] In this way, by making the Al composition ratio ybn1 of the n-side first barrier layer be 0.2 or more and 0.4 or less, it is possible to achieve low loss of the waveguide while suppressing a large decrease in the light confinement coefficient to the well layer.

[0019] Further, regarding the Al composition ratio ybp1 of the p-side barrier layer, by the establishment of the above relationship, it is possible to suppress the energy difference ΔEv2 of the valence band potential energy between the n-side first barrier layer and the p-side barrier layer to be 30 meV or less, and increase the energy difference ΔEc2 of the conduction band potential energy between the n-side first barrier layer and the p-side barrier layer to be 25 meV or more. Thus, by suppressing the energy difference ΔEv2, it is possible to suppress an increase in the operating voltage, and by increasing the energy difference ΔEc2, it is possible to suppress overflow of electrons.

[0020] Further, by setting the Al composition ratio xbp1 of the p-side barrier layer to be 0.15 or less, it is possible to suppress the lattice mismatch between the GaAs substrate and the p-side barrier layer to be a maximum of 1.2%.

[0021] Further, in the technical solution of the semiconductor light emitting element of the present application, it can be that further, 0.2≦ybn1≦0.4, ybp1≦xbp1+0.975ybn1+0.069, ybp1≧0.4xbp1+0.975ybn1+0.029, and xbp1≦0.15. ykp1 Ga 1-ykp1 As is represented; the relationship of ybp1≦xbp1+0.975ykp1+0.069, ybp1≧0.4xbp1+0.975ykp1+0.029, and 0.2≦ykp1≦0.4 is established.

[0022] In the case where the above relationship is established regarding the Al composition ratio ybp1 of the p-side barrier layer, the energy difference ΔEc2 of 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 of the valence band potential energy is 30 meV or less. Thus, it is possible to suppress a situation that hinders injection of holes to the well layer, so it is possible to suppress an increase in the operating voltage. Further, it is possible to suppress overflow of electrons from the well layer.

[0023] Further, by setting the Al composition ratio of the p-side intermediate layer to be 0.2 or more and 0.4 or less, it is possible to control the light distribution in the vertical direction with higher precision, and it is possible to achieve low loss of the waveguide while increasing the light confinement coefficient.

[0024] Further, by providing the p-side intermediate layer composed of the AlGaAs layer which is substantially lattice-matched with the GaAs substrate between the well layer and the p-side barrier layer, the formation region of the compressive strain near the active layer can be dispersed, so that the decrease in the crystallinity due to the concentration of the compressive strain can be suppressed.

[0025] Further, since the energy difference ΔEv of the valence band potential energy between the well layer and the p-side intermediate layer can be reduced, the formation of the light hole of the high-order energy level can be suppressed. Thus, the decrease in the polarization ratio can be suppressed.

[0026] Further, in one technical solution of the semiconductor light emitting element of the present application, it can be that a n-side second barrier layer provided between the n-side first barrier layer and the well layer is further provided; the composition of the n-side second barrier layer is represented by Al ybn2 Ga 1-xbn2-ybn2 In xbn2 As; the relations of ybn2≧xbn2+ybn1, ybn2≦0.4xbn2+0.975ybn1+0.061, xbn2≦0.15, and 0.2≦ybn1≦0.35 are established.

[0027] In the case where the relations are established with respect to the Al composition ratio ybn2 of the n-side second barrier layer, the energy difference ΔEc2 of 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 of the valence band potential energy is 30 meV or more. Thus, the case where the injection of the electron to the well layer is hindered can be suppressed, so that the increase in the operating voltage can be suppressed. Further, the overflow of the hole from the well layer can be suppressed.

[0028] Further, by making the Al composition ratio of the n-side first barrier layer relatively low, 0.2 or more and 0.35 or less, the refractive index of the n-side first barrier layer can be increased, so that the light distribution in the vertical direction can be easily made close to the n-type semiconductor layer side. Thus, the low-loss of the waveguide becomes easy.

[0029] Further, in one technical solution of the semiconductor light emitting element of the present application, it can be that a n-side third barrier layer provided between the well layer and the n-side second barrier layer is further provided; the composition of the n-side third barrier layer is represented by Al ybn3 Ga 1- ybn3 As; the relations of ybn2≧xbn2+ybn3, ybn2≦0.4xbn2+0.975ybn3+0.061, and 0.2≦ybn3≦0.35 are established.

[0030] In the case where the above relationship holds with respect to the Al composition ratio ybn2 of the n-side second barrier layer, 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. Further, by setting the Al composition ratio of the n-side third barrier layer to 0.35 or less, the band gap energy of the n-side third barrier layer can be reduced. Thus, the case where the injection of electrons into the well layer is hindered can be suppressed, so the increase in the operating voltage can be suppressed.

[0031] Further, in the case where the above relationship holds with respect to the Al composition ratio ybn2 of the n-side second barrier layer, the energy difference ΔEv2 of the valence band potential energy between the n-side second barrier layer and the n-side third barrier layer is 0 meV or more. Thus, the overflow of holes from the well layer can be suppressed.

[0032] Further, by making the Al composition ratio of the n-side third barrier layer low to 0.2 or more and 0.35 or less, the refractive index of the n-side third barrier layer can be made high, so the light distribution in the vertical direction can be easily made to be closer to the n-type semiconductor layer side. Thus, the low-loss of the waveguide becomes easy.

[0033] Further, in one technical solution of the semiconductor light emitting element of the present application, it can be that a p-side guide layer having a larger refractive index than the p-type clad layer is provided between the p-side barrier layer and the p-type clad layer.

[0034] Thus, by providing the p-side guide layer having a larger refractive index than the p-type clad layer on the p-side barrier layer, the light distribution in the vertical direction can be controlled with high precision, and the case where the light distribution is excessively biased to the n-type semiconductor layer side can be suppressed. Thus, the decrease in the light confinement coefficient in the vertical direction to the well layer and the increase in the operating carrier density in the well layer can be suppressed. That is, the temperature characteristics of the semiconductor light emitting element can be suppressed from deteriorating. Furthermore, if the p-side guide layer is made undoped, the increase in the free carrier loss due to impurity doping can be suppressed, so the low-loss of the waveguide can be achieved. As a result, a semiconductor laser element having good temperature characteristics and high slope efficiency can be achieved.

[0035] Further, in one technical solution of the semiconductor light emitting element of the present application, the composition of the p-side guide layer can be Al ygp1 Ga 1-ygp1 As; and the relationship ybp1≦xbp1+0.975ygp1+0.069, ybp1≧0.4xbp1+0.975ygp1+0.029, and 0.2≦ygp1≦0.4 holds.

[0036] The p-side guide layer having such a composition is substantially lattice-matched to the GaAs substrate. Thus, the film thickness of the p-side barrier layer having a compressive lattice mismatch can be made to be equal to or less than the critical film thickness. Thus, the decrease in the crystal quality of the p-side barrier layer can be suppressed.

[0037] Further, in the case where the well layer is a quaternary semiconductor material film containing Al, the compressive strain of the active layer increases. Therefore, by providing the p-side guide layer that is substantially lattice-matched with the GaAs substrate above the p-side barrier layer, the accumulation of the compressive strain in the vicinity of the active layer can be suppressed. In addition, in this case, since the potential energy between the lowest levels of the heavy hole and the light hole increases, the recombination probability of the light hole and the electron can be reduced. Thus, the TM polarized component due to the recombination of the light hole and the electron can be reduced, so that the polarization ratio is improved.

[0038] By the establishment of the above relationship, the energy difference ΔEv2 of the valence band potential energy between the p-side barrier layer and the p-side guide layer can be suppressed to 30 meV or less, and the energy difference ΔEc2 of the conduction band potential energy can be increased to 25 meV or more, so that the overflow of the electron from the well layer can be suppressed while suppressing the increase in the operating voltage.

[0039] 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 the low loss of the waveguide can be achieved while suppressing the large decrease in the light confinement coefficient.

[0040] Further, in one technical solution of the semiconductor light emitting element of the present application, the p-side guide layer can be made of (Al ygp2 Ga 1-ygp2 ) 0.5 In 0.5 P indicates.

[0041] Thus, in the p-side guide layer, vacancies or impurities such as Zn, Mg, and the like easily diffuse. Therefore, by diffusing the vacancies or impurities in the semiconductor light emitting element, when forming the facet window structure, the time required for the formation can be reduced. In addition, since the concentration of the impurities used when diffusing the impurities can be reduced, the light absorption due to the impurities can be reduced. Thus, the decrease in the light emitting efficiency of the semiconductor light emitting element can be suppressed.

[0042] Further, in one technical solution of the semiconductor light emitting element of the present application, the composition of the n-type cladding layer can be represented by Al yn1 Ga 1-yn1 As; the composition of the p-type cladding layer can be represented by Al yp1 Ga 1-yp1 As; and the relationship of 0 < yn1 < yp1 < 1 is established.

[0043] Thus, since the Al composition ratio of the n-type cladding is lower than that of the p-type cladding, the refractive index of the n-type cladding is larger than that of the p-type cladding. Consequently, the light distribution in the vertical direction is biased toward the n-type cladding side. As described above, since the free carrier loss of light from the waveguide of the semiconductor light-emitting device becomes larger in the p-type semiconductor layer having a doping concentration higher than that of the n-type semiconductor layer, by making the light distribution in the vertical direction closer to the n-type semiconductor layer, a reduction in waveguide loss can be achieved.

[0044] By biasing the light distribution toward the n-type cladding side, the light confinement factor in the vertical direction to the well layer as the light-emitting layer decreases. Therefore, as described above, electrons easily spill over from the well layer to the p-side barrier layer. However, in the semiconductor light-emitting device of the present invention, since the energy difference ΔEc between the conduction band potentials of the p-side barrier layer and the n-side first barrier layer is large, electron spillover can be suppressed. Thus, 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 compared to conventional semiconductor light-emitting devices can be achieved.

[0045] In addition, in one aspect of the semiconductor light-emitting device of the present invention, the composition of the n-type cladding may be represented by (Al yn2 Ga 1-yn2 ) 0.5 In 0.5 P; the composition of the p-type cladding may be represented by (Al yp2 Ga 1-yp2 ) 0.5 In 0.5 P; and the relationship 0 < yn2 < yp2 < 1 holds.

[0046] By providing an n-type cladding and a p-type cladding having such compositions, vacancies or impurities such as Zn and Mg easily diffuse in the n-type cladding and the p-type cladding. Thus, by diffusing vacancies or impurities in the semiconductor light-emitting device, when forming an end face window structure, 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 caused by the impurities can be reduced. Thus, a decrease in the light emission efficiency of the semiconductor light-emitting device can be suppressed.

[0047] In addition, by the relationship 0 < yn2 < yp2 < 1 holding, the refractive index of the p-type cladding can be made lower than that of the n-type cladding. Consequently, the intensity distribution of the laser can be biased toward the n-type cladding side. That is, the laser propagating in the p-type cladding can be reduced, so free carrier loss caused by impurities in the p-type cladding can be reduced. Thus, low-loss waveguide can be achieved.

[0048] In addition, in one aspect of the semiconductor light-emitting device of the present invention, the composition of the well layer may be Al ywGa 1-xw-yw In xw As represents; 0≦yw<1 and 0<xw<1.

[0049] Thus, in the case where the composition of the well layer is Al yw Ga 1-xw-yw In xw As, by adjusting the Al composition ratio, the Ga composition ratio and the In composition ratio of the well layer, the magnitude of the strain of the well layer, the energy difference of the conduction band and the valence band of the well layer and each barrier layer can be adjusted. Thus, adjustment of the oscillation wavelength of the semiconductor light emitting element and control of the overflow of the electrons from the well layer can be performed.

[0050] Further, in one technical solution of the semiconductor light emitting element of the present application, further, the relationship of 0<yw<1 can be established.

[0051] Thus, the well layer contains Al, and thus in the case where the well layer has a compressive strain, the number of light holes formed in the valence band of the well layer can be reduced. Here, the light generated by the recombination of the light hole (LH) and the electron is greater in the proportion of the TM mode light than the light generated by the recombination of the heavy hole (HH) and the electron. Thus, by reducing the number of light holes formed in the valence band of the well layer, the recombination probability of the light hole and the electron can be reduced, and thus 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.

[0052] Further, in one technical solution of the semiconductor light emitting element of the present application, the above substrate can be a GaAs substrate.

[0053] Thus, by using the GaAs substrate as the substrate, in the case where the quaternary semiconductor material of the AlGaInAs type is used as the barrier layer and the well layer, the well layer can be made to have a compressive strain. In the case where the well layer has a compressive strain, by adjusting the composition of the well layer, the number of light holes formed in the valence band of the well layer can be reduced. Thus, the recombination probability of the light hole and the electron can be reduced, and thus the polarization ratio of the output light from the semiconductor light emitting element can be increased.

[0054] Further, in one technical solution of the semiconductor light emitting element of the present application, the band gap energy of the n-type clad layer can be smaller than the band gap energy of the p-type clad layer.

[0055] Thus, the refractive index of the n-type clad layer is higher than the refractive index of the p-type clad layer. Therefore, the light distribution in the direction perpendicular to the main surface of the substrate is biased to the n-type clad layer side. Here, in the n-type semiconductor layer, by setting the doping concentration of the n-type impurities to 1 x 10 16 cm -3 The above, 1 x 10 18 cm -3The following range is capable of suppressing the resistance value. On the other hand, in the p-type semiconductor layer, if the doping concentration of the p-type impurity is not set to 1 x 10 18 cm -3 The above cannot suppress the resistance value. Thus, the free carrier loss of the waveguide of light from the semiconductor light emitting element becomes large in the p-type semiconductor layer having a higher doping concentration than the n-type semiconductor layer. Therefore, by making the light distribution biased toward the n-type cladding layer side as in the semiconductor light emitting element of the present application, the waveguide loss can be reduced.

[0056] By making the light distribution biased toward the n-type cladding layer side, the light confinement coefficient in the vertical direction (a direction perpendicular to the main surface of the substrate) of the well layer as the light emitting layer decreases. Therefore, in the case of laser oscillation in the semiconductor light emitting element, the working carrier in the well layer increases, and the electron, which has a smaller effective mass than the hole, easily overflows from the well layer to the p-side barrier layer. However, in the semiconductor light emitting element of the present application, since the energy difference ΔEc of the conduction band potential of the p-side barrier layer and the n-side first barrier layer is large, the overflow of the electron can be suppressed. Thus, a semiconductor light emitting element capable of improving the temperature characteristics while suppressing the increase in the operating voltage, and having a high slope efficiency at a low operating current can be realized.

[0057] Further, in one technical solution of the semiconductor light emitting element of the present application, it can be that an end face window structure is formed in the light emission end surface portion of the active layer.

[0058] Among AlAs, GaAs, and InAs, the InAs lattice constant is the largest, and the band gap energy is the smallest. In the case where a quaternary semiconductor material of the AlGaInAs type is used for the well layer and each barrier layer to obtain a desired band gap energy as in the semiconductor light emitting element of the present application, since the In content of the well layer composed of AlGaInAs increases compared to the case where a semiconductor material composed of InGaAs is used for the well layer to obtain a desired band gap energy, the compressive strain of the well layer becomes large.

[0059] Further, in the case of using a nitride-based semiconductor material, among AlN, GaN, and InN, the InN lattice constant is the largest, and the band gap energy is the smallest. In this case, in the case where a layer containing a quaternary semiconductor material composed of AlGaInN is used for the well layer and each barrier layer to obtain a desired band gap energy, since the In content of the well layer composed of AlGaInN increases compared to the case where a semiconductor material composed of InGaN or AlGaN is used for the well layer to obtain a desired band gap energy, the compressive strain of the well layer becomes large.

[0060] According to the above, in a configuration in which AlGaInAs, AlGaInN, or the like is used for the well layer and each barrier layer, in a case in which a vacancy or an impurity diffuses to the light exit end surface portion of the semiconductor light emitting element, the strain energy of the well layer becomes small, and the In atoms of the well layer easily exchange with the Al atoms and Ga atoms that exist at the lattice positions of Group III with respect to the stacking direction. Thus, the band gap energy of the well layer easily becomes large.

[0061] As a result, the band gap energy of the well layer of the light exit end surface portion, which has a large optical density, becomes large, and a so-called window configuration can be formed. Thus, even if the band gap energy of the light exit end surface portion becomes small due to heat generation, a state in which the light absorption of the well layer of the light exit end surface portion is small can be maintained. Thus, the occurrence of COD (Catastrophic Optical Damage) due to the absorption of light by the light exit end surface portion can be suppressed.

[0062] Further, if a window configuration is formed by vacancy diffusion, compared to a case in which a window configuration is formed by impurity diffusion, the occurrence of free carrier loss due to the presence of impurities can be suppressed, and thus the decrease in the slope efficiency can be suppressed.

[0063] Further, in one technical aspect of the semiconductor light emitting element of the present application, the band gap energy of a portion of the active layer in which the end surface window configuration is formed can be larger than the band gap energy of a portion of the active layer in which the end surface window configuration is not formed.

[0064] Thus, even if the band gap energy of the light exit end surface portion becomes small due to heat generation, a state in which the light absorption of the well layer of the light exit end surface portion is small can be maintained. Thus, the occurrence of COD due to the absorption of light by the light exit end surface portion can be suppressed.

[0065] Further, in order to solve the above problem, one technical aspect of the method of manufacturing a semiconductor light emitting element of the present application includes: a step of preparing a substrate; a step of forming an n-type cladding layer above the substrate; a step of forming an active layer above the n-type cladding layer; a step of forming a p-type cladding layer above the active layer; and a step of forming an end surface window configuration in the active layer; 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; 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; and in the step of forming the end surface window configuration, a vacancy or an impurity is diffused in the active layer.

[0066] Thus, a semiconductor light emitting element can be manufactured in which the In composition ratio of the n-side first barrier layer is smaller than the In composition ratio of the p-side barrier layer, and the band gap of the n-side first barrier layer is smaller than the band gap of the p-side barrier layer. According to such a semiconductor light emitting element, the energy difference ΔEc of the conduction band potential of the p-side barrier layer and the n-side first barrier layer can be made larger than the energy difference ΔEv of the valence band potential of the p-side barrier layer and the n-side first barrier layer. Thus, an increase in voltage required for electrical conduction of holes, that is, an increase in operating voltage of the semiconductor light emitting element can be suppressed, and overflow of electrons from the well layer can be suppressed.

[0067] Further, for example, in a configuration in which AlGaInAs, AlGaInN, or the like is used for the well layer and each barrier layer, in a case in which a vacancy or an impurity is diffused in the light emission end surface portion of the semiconductor light emitting element, the strain energy of the well layer becomes small, and thus In atoms of the well layer easily exchange with Al atoms and Ga atoms that exist in the lattice position of Group III with respect to the stacking direction. Thus, the band gap energy of the well layer easily becomes large.

[0068] As a result, the band gap energy of the well layer of the light emission end surface portion in which the optical density is large becomes large, and a facet window configuration can be formed. Thus, even if the band gap energy of the light emission end surface portion becomes small due to heat generation, a state in which the light absorption of the well layer of the light emission end surface portion is small can be maintained. Thus, occurrence of COD due to absorption of light by the light emission end surface portion can be suppressed.

[0069] Effects of Invention

[0070] According to the present application, a semiconductor light emitting element or the like in which overflow of electrons from a well layer is suppressed while an operating voltage is suppressed can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1 is a schematic cross-sectional view that shows the entire configuration of the semiconductor light emitting element of Embodiment 1.

[0072] Figure 2 is a schematic cross-sectional view that shows the detailed configuration of the active layer provided in the semiconductor light emitting element of Embodiment 1.

[0073] Figure 3 is a schematic view that shows an outline of the band structure of the active layer of the comparative example.

[0074] Figure 4 is a schematic view that shows an outline of the band structure of the active layer of Embodiment 1.

[0075] Figure 5 is a schematic view that shows the energy difference of each of the conduction band potential and the valence band potential of the n-side first barrier layer and the p-side barrier layer of the active layer of Embodiment 1.

[0076] Figure 6is a graph showing the In and Al composition ratio dependence of the band gap energy (Eg) of AlGaInAs-based materials.

[0077] Figure 7 is a graph showing the In and Al composition ratio dependence of the valence band potential energy of AlGaInAs-based materials.

[0078] Figure 8 is a graph showing the In and Al composition ratio dependence of the conduction band potential energy of AlGaInAs-based materials.

[0079] Figure 9 is a graph showing the relationship between the energy difference ΔEc2 of the conduction band potential energy and the energy difference ΔEv2 of the valence band potential energy between AlGaInAs-based materials and Al 0.2 Ga 0.8 As and the composition of the AlGaInAs-based materials.

[0080] Figure 10 is a graph showing the relationship between the energy difference ΔEc2 of the conduction band potential energy and the energy difference ΔEv2 of the valence band potential energy between AlGaInAs-based materials and Al 0.3 Ga 0.7 As and the composition of the AlGaInAs-based materials.

[0081] Figure 11 is a graph showing the relationship between the energy difference ΔEc2 of the conduction band potential energy and the energy difference ΔEv2 of the valence band potential energy between AlGaInAs-based materials and Al 0.4 Ga 0.6 As and the composition of the AlGaInAs-based materials.

[0082] Figure 12 is a graph showing the simulation results of the current-voltage characteristics of the semiconductor light emitting element of Comparative Example 1.

[0083] Figure 13 is a graph showing the simulation results of the current-voltage characteristics of the semiconductor light emitting element of Comparative Example 2.

[0084] Figure 14 is a graph showing the simulation results of the current-voltage characteristics of the semiconductor light emitting element of Embodiment 1.

[0085] Figure 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 elements of Comparative Example 1, Comparative Example 2, and Embodiment 1.

[0086] Figure 16 is a first graph showing the calculation results of the relationship between the Al composition ratio of the well layer and the heavy hole energy level and the light hole energy level of Embodiment 1.

[0087] Figure 17 FIG. 3 is a second graph showing the relationship between the Al composition ratio of the well layer of Embodiment 1 and the heavy hole energy level and the light hole energy level, which is a calculation result.

[0088] Figure 18 FIG. 4 is a third graph showing the relationship between the Al composition ratio of the well layer of Embodiment 1 and the heavy hole energy level and the light hole energy level, which is a calculation result.

[0089] Figure 19 FIG. 5 is a schematic view showing an outline of the band structure of the semiconductor light emitting element of Modification 1 of Embodiment 1.

[0090] Figure 20 FIG. 6 is a schematic view showing the energy difference ΔEc2 and ΔEv2 of the conduction band potential and the valence band potential, respectively, between the p-side barrier layer and the p-side guide layer of Modification 1 of Embodiment 1.

[0091] Figure 21 FIG. 7 is a graph showing the relationship between the Al composition ratio of the p-side barrier layer of Modification 1 of Embodiment 1 and the energy difference ΔEc2 and ΔEv2.

[0092] Figure 22 FIG. 8 is a schematic view showing an outline of the band structure of the semiconductor light emitting element of Modification 2 of Embodiment 1.

[0093] Figure 23 FIG. 9 is a schematic view showing an outline of the band structure of the semiconductor light emitting element of Modification 3 of Embodiment 1.

[0094] Figure 24 FIG. 10 is a schematic view showing an outline of the band structure of the semiconductor light emitting element of Modification 4 of Embodiment 1.

[0095] Figure 25 FIG. 11 is a schematic view showing an outline of the band structure of the semiconductor light emitting element of Modification 5 of Embodiment 1.

[0096] Figure 26 FIG. 12 is a schematic view showing an outline of the band structure of the semiconductor light emitting element of Modification 6 of Embodiment 1.

[0097] Figure 27 FIG. 13 is a sectional view showing the structure of the light emission end surface portion of the semiconductor light emitting element of Modification 7 of Embodiment 1.

[0098] Figure 28 FIG. 14 is a schematic sectional view showing the overall structure of the semiconductor light emitting element of Embodiment 2.

[0099] Figure 29 FIG. 15 is a schematic sectional view showing the overall structure of the semiconductor light emitting element of Embodiment 3.

[0100] Figure 30 is a schematic cross-sectional view that shows the dimensions of each part of the semiconductor light emitting element of Embodiment 3.

[0101] Figure 31 is a schematic cross-sectional view that shows the mounting state of the semiconductor light emitting element of Embodiment 3.

[0102] Figure 32 is a graph that shows the distribution of the shear stress σxy corresponding to the position in the x-axis direction of the active layer of the semiconductor light emitting element of Embodiment 3.

[0103] Figure 33 is a flowchart that shows the process of the manufacturing method of the semiconductor light emitting element of Embodiment 4. DETAILED DESCRIPTION

[0104] Hereinafter, the embodiments of the present application will be described with reference to the drawings. In addition, each of the embodiments described below shows one specific example of the present application. Thus, the numerical values, shapes, materials, component configurations, arrangement positions, and connection modes, and the like shown in the following embodiments are shown as one example and are not intended to limit the present application.

[0105] Further, each of the drawings is a schematic view and is not necessarily strictly illustrated. Thus, the scale and the like are not necessarily consistent in each of the drawings. In addition, in each of the drawings, the same reference numerals are assigned to substantially the same structures, and repeated description will be omitted or simplified.

[0106] Further, in the present specification, the terms "upper" and "lower" do not refer to the upper (vertically upward) and lower (vertically downward) in the absolute spatial recognition, but are used as terms specified by the relative positional relationship based on the stacking order in the stacked structure. In addition, the terms "upper" and "lower" are applicable not only to the case where two component elements are arranged apart from each other with a space and there is another component element between the two component elements, but also to the case where the two component elements are arranged in a state of being in contact with each other.

[0107] (Embodiment 1)

[0108] The semiconductor light emitting element of Embodiment 1 will be described.

[0109] [1-1. Overall structure]

[0110] First, the overall structure of the semiconductor light emitting element of the present embodiment will be described using FIG. 1. Figure 1 and Figure 2 The overall structure of the semiconductor light emitting element of the present embodiment will be described. Figure 1 is a schematic cross-sectional view that shows the overall structure of the semiconductor light emitting element 1 of the present embodiment. Figure 2This is a schematic cross-sectional view showing the detailed structure of the active layer 14 provided in the semiconductor light-emitting element 1 of this embodiment.

[0111] The semiconductor light-emitting element 1 is a device that emits light by applying a voltage. In this embodiment, the semiconductor light-emitting element 1 is a semiconductor laser element that emits laser light with a wavelength of approximately 900 nm to 980 nm. More specifically, the semiconductor light-emitting element 1 emits laser light with a wavelength of approximately 915 nm. Figure 1 This represents a cross-section of the semiconductor light-emitting element 1 perpendicular to the resonant direction of the laser. The distance between the end faces of the resonator of the semiconductor light-emitting element 1 along the resonant direction of the laser is not particularly limited, but in this embodiment it is 2 mm or more. Furthermore, the resonator length of the semiconductor light-emitting element 1 can also be 4 mm or more. By increasing the resonator length, the thermal resistance of the semiconductor light-emitting element 1 can be reduced, thus improving heat dissipation. Therefore, the light output at thermal saturation of the semiconductor light-emitting element 1 can be increased. Figure 1 As shown, 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-restricting layer 19, a contact layer 18, an n-side electrode 31, and a p-side electrode 32.

[0112] The substrate 10 is a plate-shaped component that serves as the base of the semiconductor light-emitting element 1. In this embodiment, the substrate 10 is an n-type GaAs substrate.

[0113] The buffer layer 11 is used to suppress strain caused by the lattice mismatch between the substrate 10 and the n-type cladding layer 12. The structure of the buffer layer 11 is not particularly limited; in this embodiment, the buffer layer 11 is an n-type GaAs layer with a thickness of 0.5 μm. The buffer layer 11 is doped with an impurity concentration of 3 × 10⁻⁶. 17 cm -3 Si.

[0114] The n-type cladding layer 12 is an n-type cladding layer disposed above the substrate 10. The n-type cladding layer 12 has a lower refractive index and a higher bandgap energy compared to the active layer 14. The structure of the n-type cladding layer 12 is not particularly limited; in this embodiment, the n-type cladding layer 12 is an n-type Al film with a thickness of 4 μm. 0.305 Ga 0.695 As layer. In the n-type cladding 12, it is doped as an impurity with a concentration of 1×10⁻⁶. 18 cm -3 Si.

[0115] The active layer 14 is disposed above the n-type cladding layer 12 and is a light-emitting layer with a quantum well structure. In this embodiment, the active layer 14 is as follows: Figure 2 As shown, it has an n-side first barrier layer 14a, a well layer 14d, and a p-side barrier layer 14f.

[0116] 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 the present embodiment, the well layer 14d is an Al 0.08 Ga 0.67 In 0.25 As layer having a film thickness of 6 nm.

[0117] 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 the present embodiment, the n-side first barrier layer 14a is an Al 0.27 Ga 0.73 As layer having a film thickness of 7 nm.

[0118] 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 the present embodiment, the p-side barrier layer 14f is an Al 0.45 In 0.10 Ga 0.45 As layer having a film thickness of 7 nm. The film thickness of the p-side barrier layer 14f is set so that, in an end surface on the p-type cladding layer 17 side of the p-side barrier layer 14f, the wave function of the electron within the well layer 14d is attenuated to less than 1% of the maximum amplitude. Thereby, it is possible to suppress the electron within the well layer 14d from penetrating the p-side barrier layer 14f, i.e., to generate a leakage current, due to a tunnel effect. Further, the p-side barrier layer 14f has a compressive strain, and if the critical film thickness is exceeded, a lattice defect occurs. Therefore, the film thickness of the p-side barrier layer 14f can also be 3 nm or more so that it is possible to suppress the electron within the well layer 14d from penetrating due to a tunnel effect, and 20 / Q or less of the critical film thickness. Here, if the absolute value of the lattice mismatch of the p-side barrier layer 14f with respect to the substrate 10 is Q%, the critical film thickness can be set to 20 / Q.

[0119] The p-type cladding layer 17 is a cladding layer of the p-type disposed above the active layer 14. The p-type cladding layer 17 is a layer having a low refractive index and a high band gap energy compared to the active layer 14. The structure of the p-type cladding layer 17 is not particularly limited, and in the present embodiment, the p-type cladding layer 17 is a p-type Al 0.7 Ga 0.3 As layer having a film thickness of 0.7 μm. In the p-type cladding layer 17, C (carbon atom) is doped as an impurity at a concentration of 2 x 1018cm-3. 18 cm -3 -3.

[0120] The contact layer 18 is a layer disposed above the p-type cladding layer 17, and is in contact with the p-electrode 32. The structure of the contact layer 18 is not particularly limited, and in the present embodiment, the contact layer 18 is a p-type GaAs layer having a film thickness of 0.4 μm. In the contact layer 18, C is doped as an impurity at a concentration of 2 x 1018cm-3. 18 cm -3 -3.

[0121] The current-narrowing layer 19 is a layer disposed above the p-type clad layer 17, which functions to cause current to flow concentratedly in a narrow region in the semiconductor light emitting element 1, that is, to confine current in a part of a region. In the present embodiment, the current-narrowing layer 19 is an n-type semiconductor layer disposed between the p-type clad layer 17 and the contact layer 18. The current-narrowing layer 19 has an opening portion 19a in a long size shape along the laser resonant direction of the semiconductor light emitting element 1. The contact layer 18 is disposed in the opening portion 19a. Thereby, current flows only in the opening portion 19a of the current-narrowing layer 19. That is, current is confined in the opening portion 19a. In consequence, current flows in a region below the opening portion 19a in the active layer 14, so the region becomes a light emitting portion. The structure of the current-narrowing layer 19 is not particularly limited, and in the present embodiment, the current-narrowing layer 19 is an n-type GaAs layer having a film thickness of 0.25 μm. In the current-narrowing layer 19, Si is doped as an impurity at a concentration of 2 x 1018cm-2. 18 cm -3

[0122] The n-side electrode 31 is an electrode disposed on a lower main face of the substrate 10, that is, a main face of the substrate 10 on the back side of the main face of the substrate 10 on which the semiconductor layers are stacked. The structure of the n-side electrode 31 is not particularly limited, and in the present embodiment, the n-side electrode 31 includes, in order from the substrate 10 side, an AuGe film having a film thickness of 90 nm, a Ni film having a film thickness of 20 nm, an Au film having a film thickness of 50 nm, a Ti film having a film thickness of 100 nm, a Pt film having a film thickness of 50 nm, a Ti film having a film thickness of 50 nm, a Pt film having a film thickness of 100 nm, and an Au film having a film thickness of 500 nm.

[0123] 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. The structure of the p-side electrode 32 is not particularly limited, and in the present embodiment, the p-side electrode 32 includes, in order from the contact layer 18 side, a Ti film having a film thickness of 50 nm, a Pt film having a film thickness of 150 nm, and an Au film having a film thickness of 50 nm.

[0124] [1-2. Action and effects]

[0125] Next, the action and effects of the semiconductor light emitting element 1 of the present embodiment will be described.

[0126] [1-2-1. Action and effects of active layer]

[0127] First, the action of the semiconductor light emitting element of the comparative example will be compared while the outline of the action and effects of the active layer 14 of the semiconductor light emitting element 1 of the present embodiment will be described using Figure 3 and Figure 4 Figure 3 and Figure 4 ​​These are schematic diagrams illustrating the outline of the band structure of each active layer in the comparative example and this embodiment, respectively. Additionally, in Figure 3 and Figure 4 The diagram also represents the energy difference ΔEc between the conduction band potential of the p-side barrier layer and the well layer, the energy difference ΔEv between the valence band potential, the Fermi level Efe for electrons, and the Fermi level Efh for holes. Furthermore, in... Figure 4 The figure also represents the energy difference ΔEfc between the electron's Fermi level Efe and the conduction band potential of the p-side barrier layer 14f, and the energy difference ΔEfv between the hole's Fermi level Efh and the valence band potential of the p-side barrier layer 14f.

[0128] Figure 3 The active layer of the comparative example shown is the same as the active layer 14 of this embodiment, having an n-side first barrier layer 14a, a well layer 14d, and a p-side barrier layer. The composition of the p-side barrier layer in the comparative example differs from that of the p-side barrier layer 14f of this embodiment. The p-side barrier layer in the comparative example is an AlGaAs layer and does not contain In.

[0129] Regarding the active layer of a comparative example having such a p-side barrier layer, the case where the energy difference ΔEc is increased to suppress electron overflow was investigated. In this case, the energy difference ΔEc can be increased by increasing the Al composition ratio of the p-side barrier layer. However, the energy difference ΔEv also increases accordingly. Consequently, the energy required for holes to cross the p-side barrier layer also increases, thus increasing the operating voltage of the semiconductor light-emitting element.

[0130] On the other hand, Figure 4 In the active layer 14 of this embodiment shown, the p-side barrier layer 14f contains In, and the In content of the n-side first barrier layer 14a is lower than that of the p-side barrier layer 14f. Furthermore, the band gap energy of the n-side first barrier layer 14a is lower than that of the p-side barrier layer 14f. Through such an active layer 14, as... Figure 4 As shown, the energy differences ΔEc and ΔEfc can be increased while suppressing the increase of energy differences ΔEv and ΔEfv. Therefore, the increase of the operating voltage of the semiconductor light-emitting element 1 can be suppressed by suppressing the increase of energy differences ΔEv and ΔEfv, and electron overflow can be suppressed by increasing energy differences ΔEc and ΔEfc.

[0131] Regarding the characteristics of the active layer 14 in this embodiment described above, using Figures 5-8 A detailed explanation will be provided. Figure 5 This is a schematic diagram showing the energy difference between the conduction band potential energy and the valence band potential energy of the n-side first barrier layer 14a and the p-side barrier layer 14f of the active layer 14 in this embodiment. Figure 5As shown, the energy difference ΔEcb and ΔEcb of the conduction band potential and the valence band potential of the n-side first barrier layer 14a and the p-side barrier layer 14f are defined. Figure 6 , Figure 7 and Figure 8 are graphs showing the In and Al composition ratio dependence of the band gap energy (Eg), the valence band potential, and the conduction band potential of the AlGaInAs-based material, respectively. In Figure 6 , Figure 7 and Figure 8 , the vertical axis represents the band gap energy, the valence band potential, and the conduction band potential, respectively, and the horizontal axis represents the In composition ratio. Further, in Figures 6-8 , a graph showing the case where the Al composition ratio is changed every 0.1 from 0 to 1 is shown.

[0132] As shown in Figure 6 , the larger the In composition ratio, the smaller the band gap energy, and the larger the Al composition ratio, the larger the band gap energy. For example, the band gap energy of Ga 0.7 In 0.3 As is about 1.0 eV, and the band gap energy of Al 0.4 In 0.6 As is about 1.23 eV. The energy difference ΔEcb and ΔEcb is about 0.23 eV (ΔEg shown in Figure 6 ), that is, the sum of the energy difference ΔEcb and ΔEcb is about 0.23 eV. Thus, in the AlGaInAs-based material, even if the In composition ratio is increased, the band gap energy can be made larger by increasing the Al composition ratio.

[0133] As shown in Figure 7 and Figure 8 , the larger the In composition ratio, the higher the valence band potential and the lower the conduction band potential. On the other hand, the larger the Al composition ratio, the lower the valence band potential and the higher the conduction band potential. Further, the change amount of the conduction band potential is larger than that of the valence band potential in correspondence with the change of the Al composition ratio and the In composition ratio. For example, the valence band potential of Ga 0.7 In 0.3 As is about -5.35 eV, and the valence band potential of Al 0.4 In 0.6 As is about -5.41 eV. The energy difference ΔEcb is about 0.06 eV, and the energy difference ΔEcb is about 0.16 eV with respect to this. In this case, the energy difference ΔEcb is 2.7 times the energy difference ΔEcb. Thus, in the AlGaInAs-based material, the conduction band potential can be made to change more than the valence band potential by adjusting the Al composition ratio and the In composition ratio. Thus, in the n-side first barrier layer 14a and the p-side barrier layer 14f, by using the AlGaInAs-based material and adjusting the respective compositions, as shown in Figure 4As shown, it is possible to increase the energy differences ΔEcand ΔEfcwhile suppressing an increase in the energy differences ΔEvand ΔEfv. 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 band gap energy of the n-side first barrier layer 14a is smaller than the band gap energy of the p-side barrier layer 14f. Thus, it is possible to increase the energy differences ΔEcand ΔEfcwhile suppressing an increase in the energy differences ΔEvand ΔEfv. As a result, it is possible to suppress the overflow of electrons from the well layer while suppressing an increase in the voltage required for the electric conduction of holes, that is, an increase in the operating voltage of the semiconductor light emitting element.

[0134] Further, if the Al composition ratio and the In composition ratio of the n-side first barrier layer 14a are set to ybn1and xbn1, respectively, the composition of the n-side first barrier layer 14a is represented by Al ybn1 Ga 1-xbn1-ybn1 In xbn1 As shown. If the Al composition ratio and the In composition ratio of the p-side barrier layer 14f are set to ybp1and xbp1, respectively, the composition of the p-side barrier layer 14f is represented by Al ybp1 Ga 1-xbp1-ybp1 In xbp1 As shown. In the present embodiment, with respect to these composition ratios, the relationships 0≦ybn1<1, 0≦xbn1<1, 0<ybp1<1, 0<xbp1<1, and xbn1<xbp1are established. By adopting the n-side first barrier layer 14a and the p-side barrier layer 14f having such compositions, it is 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 to make the band gap of the n-side first barrier layer 14a smaller than the band gap of the p-side barrier layer 14f.

[0135] Further, in the present embodiment, with respect to the Al composition ratio, the relationship ybn1<ybp1is established. Thus, the energy difference ΔEcbetween the conduction band potential of the p-side barrier layer 14f and the n-side first barrier layer 14a is increased, so it is possible to further suppress the overflow of electrons from the well layer 14d.

[0136] Further, in the present embodiment, if the Al composition ratio and the In composition ratio of the well layer 14d are set to xw and yw, respectively, the composition of the well layer 14d is represented by Al yw Ga 1-xw-yw In xw As shown, the relationships 0≦yw<1 and 0<xw<1 are established. In this way, the composition of the well layer 14d is Al yw Ga 1-xw-yw In xwAs in the case of the well layer 14d, by adjusting the Al composition ratio, the Ga composition ratio, and the In composition ratio of the well layer 14d, the magnitude of the strain of the well layer 14d and the potential energy difference of the conduction band and the valence band between the well layer 14d and each barrier layer can be adjusted. Thus, the oscillation wavelength of the semiconductor light emitting element 1 can be adjusted and the overflow of electrons from the well layer 14d can be controlled.

[0137] 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 of the present embodiment will be described using FIG. 9. Figures 9-11 A more detailed description will be given. Figure 9 , Figure 10 and Figure 11 are graphs showing the relationship between the energy difference ΔEc2 of the conduction band potential energy and the energy difference ΔEv2 of the valence band potential energy between AlGaInAs-based materials and Al 0.2 Ga 0.8 As, Al 0.3 Ga 0.7 As, and Al 0.4 Ga 0.6 As and the composition of the AlGaInAs-based material. Figures 9-11 The horizontal axis and the vertical axis of FIG. 9 respectively show the In composition ratio x and the Al composition ratio y of the AlGaInAs-based material. In Figures 9-11 , 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 Figure 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. Further, in Figure 9 , the relationship between the In composition ratio x and the Al composition ratio y at which 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 a solid line, respectively.

[0138] For example, in order to suppress the overflow of electrons from the well layer 14d, in order to make the energy difference of the conduction band potential energy of the n-side first barrier layer 14a composed of Al 0.2 Ga 0.8 As and the p-side barrier layer 14f composed of Al y Ga 1-x-y In x As be 25 meV or more, the relationship between the In composition ratio x and the Al composition ratio y of the n-side first barrier layer 14a and the p-side barrier layer 14f is determined as shown in FIG. 9. Figure 9The component ratios x and y of In and Al are given by the points on and above the line y = 0.4x + 0.225, where ΔEc² is 25 meV. In other words, the relationship y ≥ 0.4x + 0.225 holds true for both In component ratio x and Al component ratio y.

[0139] Furthermore, in order to suppress the increase in the operating voltage of the semiconductor light-emitting element 1, in order to make the Al 0.2 Ga 0.8 The first barrier layer 14a on the n-side composed of As and Al y Ga 1-x-y In x The energy difference of the valence band potential energy of the p-side barrier layer 14f composed of As is below 30 meV, and it adopts the same... Figure 9 The ratios of component In (x) and component Al (y) can be determined by the points on and below the line y = x + 0.265, where ΔEv2 is 30 meV. In other words, the relationship y ≦ x + 0.265 holds true for both component In (x) and component Al (y).

[0140] In order to further suppress the increase of the operating voltage of the semiconductor light-emitting element 1, in order to make the Al 0.2 Ga 0.8 The first barrier layer 14a on the n-side composed of As and Al y Ga 1-x-y In x The energy difference of the valence band potential energy of the p-side barrier layer 14f composed of As is below 0 meV, such as Figure 9 As shown, the relationship y ≦ x + 0.2 holds true for the In component ratio x and the Al component ratio y. Furthermore, to further suppress electron overflow from the well layer 14d, and to ensure that the Al... 0.2 Ga 0.8 The first barrier layer 14a on the n-side composed of As and Al y Ga 1-x-y In x The energy difference of the conduction band potential energy of the p-side barrier layer 14f composed of As is above 50 meV, such as Figure 9 As shown, the relationship that y ≧ 0.4x + 0.255 holds true for the ratio of In component x and the ratio of Al component y.

[0141] Therefore, when using Al 0.2 Ga 0.8 In the case of the first barrier layer 14a on the n-side composed of As, in order to suppress the increase of the operating voltage of the semiconductor light-emitting element 1 (ΔEv2≦30meV) while suppressing the leakage of electrons from the well layer 14d (ΔEc2≧25meV), regarding the Al y Ga 1-x-y In xFor the p-side barrier layer 14f composed of As, the In component ratio x and Al component ratio y must hold true for the following relationships: y ≥ 0.4x + 0.225 and y ≤ x + 0.265. The combinations of In component ratios x and Al component ratios y that hold true are... Figure 9 The points corresponding to the shaded areas shown. Furthermore, to further suppress the increase in the operating voltage of semiconductor light-emitting element 1 (ΔEv2≦0meV), the relationship y≦x+0.2 should be maintained. The combination of the In component ratio x and the Al component ratio y for which this relationship is maintained, and... Figure 9 The points in the shaded area shown correspond to the areas shaded more densely with dots. Furthermore, to further suppress electron overflow from the trap layer 14d (ΔEc2≧50meV), the relationship y≧0.4x+0.255 is further made valid.

[0142] In using Al 0.3 Ga 0.7 In the case of the first barrier layer 14a on the n-side composed of As, it is also similar to the case of using Al 0.2 Ga 0.8 Similarly, in the case of the first barrier layer 14a on the nth side formed by As, it is possible to... Figure 10 The curve shown determines the composition of the p-side barrier layer 14f. That is, in order to suppress the increase in the operating voltage of the semiconductor light-emitting element 1 (ΔEv2≦30meV) while simultaneously suppressing the leakage of electrons from the well layer 14d (ΔEc2≧25meV), as... Figure 10 As shown, regarding Al y Ga 1-x-y In x For the p-side barrier layer 14f composed of As, the In component ratio x and Al component ratio y must hold true for the conditions y ≥ 0.4x + 0.32 and y ≤ x + 0.36. The combinations of In component ratios x and Al component ratios y that hold true are... Figure 10 The points corresponding to the shaded areas are shown. Furthermore, to further suppress the increase in the operating voltage of semiconductor light-emitting element 1 (ΔEv2≦0meV), the relationship y≦x+0.3 must hold. The combination of the In component ratio x and the Al component ratio y for this relationship to hold is... Figure 10 The points in the shaded area shown correspond to the areas shaded more densely with dots. Furthermore, to further suppress electron overflow from the trap layer 14d (ΔEc2≧50meV), the relationship y≧0.4x+0.355 is further made valid.

[0143] In using Al 0.4 Ga 0.6 In the case of the first barrier layer 14a on the n-side composed of As, it is also similar to the case of using Al 0.2 Ga 0.8Similarly, in the case of the first barrier layer 14a on the nth side formed by As, it is possible to... Figure 11 The curve shown determines the composition of the p-side barrier layer 14f. That is, in order to suppress the increase in the operating voltage of the semiconductor light-emitting element 1 (ΔEv2≦30meV) while simultaneously suppressing the leakage of electrons from the well layer 14d (ΔEc2≧25meV), as... Figure 11 As shown, regarding Al y Ga 1-x-y In x For the p-side barrier layer 14f composed of As, the In component ratio x and Al component ratio y must hold true for the following relationships: y ≥ 0.4x + 0.42 and y ≤ x + 0.46. The combinations of In component ratios x and Al component ratios y that hold true are... Figure 11 The points corresponding to the shaded areas shown. Furthermore, to further suppress the increase in the operating voltage of semiconductor light-emitting element 1 (ΔEv2≦0meV), the relationship y≦x+0.4 should be maintained. The combination of the In component ratio x and the Al component ratio y for this relationship to hold is... Figure 11 The points in the shaded area shown correspond to the areas shaded more densely with dots. Furthermore, to further suppress electron overflow from the trap layer 14d (ΔEc2≧50meV), the relationship y≧0.4x+0.45 is further made valid.

[0144] Will Figures 9-11 The relationships shown are summarized as follows: if the components of the first barrier layer 14a on the nth side are represented by Al... ybn1 Ga 1-xbn1-ybn1 In xbn1 As indicates that the components of the p-side barrier layer 14f are represented by Al. ybp1 Ga 1-xbp1-ybp1 In xbp1 If As represents this, then the following relationship can be established:

[0145] 0.2≦ybn1≦0.4

[0146] ybp1≦xbp1+0.975ybn1+0.069,

[0147] ybp1≧0.4xbp1+0.975ybn1+0.029, and

[0148] xbp1≦0.15

[0149] Thus, it is possible to suppress the increase in the operating voltage of the semiconductor light emitting element 1 (ΔEv2 ≦ 30 meV) while suppressing the overflow of electrons from the well layer 14d (ΔEc2 ≧ 25 meV). Further, 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, it is possible to control the light distribution in the vertical direction with high precision, and it is possible to realize low loss of the waveguide while suppressing a large drop in the light confinement coefficient.

[0150] Further, it is also possible

[0151] the relationship ybp1 ≦ xbp1 + 0.975 ybn1 + 0.049 is satisfied. Thus, it is possible to further suppress the increase in the operating voltage of the semiconductor light emitting element 1 (ΔEv2 ≦ 20 meV).

[0152] Further, it is also possible

[0153] the relationship ybp1 ≦ xbp1 + ybn1 is satisfied. Thus, it is possible to further suppress the increase in the operating voltage of the semiconductor light emitting element 1 (ΔEv2 ≦ 0 meV).

[0154] Further, it is also possible

[0155] the relationship ybp1 ≧ 0.4 xbp1 + 0.975 ybn1 + 0.061 is satisfied. Thus, it is possible to further suppress the overflow of electrons from the well layer 14d (ΔEc2 ≧ 50 meV).

[0156] [1-2-2. Effects of the cladding]

[0157] Next, the effects of the n-type cladding layer 12 and the p-type cladding layer 17 of the present embodiment will be described.

[0158] The band gap energy of the n-type cladding layer 12 of the present embodiment is smaller than the band gap energy of the p-type cladding layer 17. Thus, the refractive index of the n-type cladding layer 12 is higher than the refractive index of the p-type cladding layer 17. Therefore, the light distribution in the direction perpendicular to the main surface of the substrate 10 is biased to the n-type cladding layer 12 side. Here, in the n-type semiconductor layer, by setting the doping concentration of the n-type impurities to 1 x 10 16 cm -3 or more and 1 x 10 18 cm -3 or less in the above and the following ranges, it is possible to suppress the resistance value. On the other hand, in the p-type semiconductor layer, if the doping concentration of the p-type impurities is not set to 1 x 10 18 cm -3The resistance value cannot be suppressed. Thus, the free carrier loss of the light from the waveguide of the semiconductor light emitting element 1 becomes large in the p-type semiconductor layer having a higher doping concentration than the n-type semiconductor layer. Therefore, by making the light distribution biased toward the n-type cladding layer 12 side as in the semiconductor light emitting element 1 of the present embodiment, the waveguide loss can be reduced.

[0159] Since the light distribution is biased toward the n-type cladding layer 12 side, the light confinement factor in the vertical direction (a direction perpendicular to the main surface of the substrate) to the well layer 14d as the light emitting layer decreases. Thus, in the case where laser oscillation occurs in the semiconductor light emitting element 1, the working carrier in the well layer 14d increases, and the electron having a smaller effective mass than the hole easily overflows from the well layer 14d to the p-side barrier layer 14f. However, in the semiconductor light emitting element 1 of the present embodiment, since the energy difference ΔEc of the conduction band potential energy between the p-side barrier layer 14f and the n-side first barrier layer 14a is large, the overflow of the electron can be suppressed. Thus, a semiconductor light emitting element capable of improving the temperature characteristics while suppressing an increase in the operating voltage, and having a low operating current and a high slope efficiency can be realized.

[0160] Further, if the Al composition ratio of the n-type cladding layer 12 is yn1, the composition of the n-type cladding layer 12 is Al yn1 Ga 1-yn1 As described above, if the Al composition ratio of the p-type cladding layer 17 is yp1, the composition of the p-type cladding layer 17 is Al yp1 Ga 1-yp1 As described above, if the Al composition ratio of the p-type cladding layer 17 is yp1, the composition of the p-type cladding layer 17 is Al

[0161] 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 is larger than the refractive index of the p-type cladding layer 17. Consequently, the light distribution in the vertical direction is biased toward the n-type cladding layer 12 side. As described above, the free carrier loss of the light from the waveguide of the semiconductor light emitting element 1 becomes large in the p-type semiconductor layer having a higher doping concentration than the n-type semiconductor layer, and thus by making the light distribution in the vertical direction close to the n-type semiconductor layer, the waveguide loss can be reduced.

[0162] Because the light distribution is biased towards the n-type cladding 12, the light confinement coefficient decreases in the direction perpendicular to the well layer 14d, which serves as the light-emitting layer. Therefore, as described above, electrons easily overflow from the well layer 14d to the p-side barrier layer 14f. However, in the semiconductor light-emitting element 1 of this embodiment, since 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, electron overflow can be suppressed. Therefore, it is possible to realize a semiconductor light-emitting element 1 with low operating current that can improve temperature characteristics and has high slope efficiency compared to conventional semiconductor light-emitting elements while suppressing the increase of operating voltage.

[0163] [1-2-3. Current-Voltage Characteristics]

[0164] Next, the current-voltage characteristics of the semiconductor light-emitting element 1 of this embodiment will be compared with those of a comparative example. Figures 12-15 Please provide an explanation. Figure 12 , Figure 13 and Figure 14 These are graphs showing the simulation results of the current-voltage characteristics of each semiconductor light-emitting element in Comparative Example 1, Comparative Example 2, and this embodiment. Figures 12-14 In the various curves, the horizontal and vertical axes represent the voltage and current applied to the semiconductor light-emitting element, respectively. Figure 15 It is a graph showing the relationship between the Al composition ratio of the quaternary barrier layer of each semiconductor light-emitting element in Comparative Example 1, Comparative Example 2 and this embodiment and the operating voltage. Figure 15 The horizontal axis of the graph represents the Al composition ratio of the quaternary barrier layer, and the vertical axis represents the operating voltage. Additionally, Figure 15 The operating voltage shown represents the operating voltage when the operating current (i.e., the current applied to the semiconductor light-emitting element) is 8A.

[0165] The semiconductor light-emitting element of Comparative Example 1 differs from the semiconductor light-emitting element 1 of this embodiment in that both the first barrier layer on the n-side and the barrier layer on the p-side are formed from the same quaternary barrier layer, namely, an AlGaInAs-type material. AlGaInAs is used as a component of the quaternary barrier layer. 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 0.55 Ga 0.35 In 0.1 As. Furthermore, in Figure 12 The document also indicates that the component Al is used. 0.3 Ga 0.7As. In addition, the composition of the well layer is Al 0.04 Ga 0.77 In 0.19 As.

[0166] The semiconductor light emitting element of Comparative Example 2 is different from the semiconductor light emitting element 1 of the present embodiment in that the n-side first barrier layer is the same quaternary barrier layer as in Comparative Example 1, and the p-side barrier layer is a ternary barrier layer. The composition of the p-side barrier layer is Al 0.3 Ga 0.7 As. In addition, in Figure 13 , the simulation results in the case where the n-side first barrier layer is a ternary barrier layer having a composition of Al 0.3 Ga 0.7 As are also shown. In addition, the composition of the well layer is the same Al 0.04 Ga 0.77 In 0.19 As.

[0167] In the semiconductor light emitting element 1 of the present embodiment, only the p-side barrier layer 14f is the same quaternary barrier layer as in Comparative Example 1, and the n-side first barrier layer 14a is a ternary barrier layer having a composition of Al 0.3 Ga 0.7 As. In addition, in Figure 14 , the simulation results in the case where the p-side barrier layer 14f is a ternary barrier layer having a composition of Al 0.3 Ga 0.7 As are also shown. In addition, the composition of the well layer 14d is the same Al 0.04 Ga 0.77 In 0.19 As.

[0168] As Figures 12-15 shown, in the semiconductor light emitting element 1 of the present embodiment, the operating voltage can be reduced as compared with the semiconductor light emitting elements of Comparative Examples 1 and 2. In particular, the greater the Al composition ratio in the quaternary barrier layer, the more remarkable the effect of reducing the operating voltage. In the semiconductor light emitting element 1 of the present embodiment, since the increase in the operating voltage can be suppressed even if the Al composition ratio of the p-side barrier layer 14f is varied, the degree of freedom in controlling the composition of the p-side barrier layer 14f can be increased. Thus, the yield in the manufacture of the semiconductor light emitting element 1 can be improved.

[0169] In addition, in the semiconductor light emitting element 1 of the present embodiment, since only the p-side barrier layer 14f is provided as a quaternary barrier layer, the increase in the operating voltage due to the composition deviation of each barrier layer can be suppressed as compared with the case where both the n-side first barrier layer 14a and the p-side barrier layer 14f are provided as quaternary barrier layers.

[0170] [1-2-4. Polarization ratio increase effect]

[0171] Next, the polarization ratio (ratio of intensity of TE mode light to intensity of TM mode light) increase effect of the present embodiment will be described.

[0172] In the semiconductor light emitting element, when a light hole and an electron recombine, the polarization ratio decreases due to generation of TM mode light. Further, in the high output operation of the conventional semiconductor light emitting element, since the active layer temperature and the operating carrier density increase, the number of light holes increases, the TM mode light component increases, and thus the polarization ratio decreases.

[0173] Further, if the resonator length of the semiconductor light emitting element becomes long, the contact area with a submount or the like on which the semiconductor light emitting element is mounted becomes large. Therefore, the strain caused by warping of the semiconductor light emitting element, unevenness of solder for mounting, and the like has a large effect on the active layer. As a result, the band structure of the active layer changes, and the number of light holes can increase.

[0174] Therefore, in the present embodiment, the energy difference between the lowest level of the light hole and the lowest level of the heavy hole is increased by increasing the compressive strain of the well layer 14d. Thereby, the number of holes existing in the light hole is reduced, and the recombination probability of the light hole and the electron is reduced. Hereinafter, the relationship between the heavy hole level and the light hole level of the well layer 14d of the present embodiment and the composition of the well layer 14d will be described using the following table. Figures 16-18

[0175] Figures 16-18 is a graph showing the calculation results of the relationship between the Al composition ratio of the well layer 14d of the present embodiment and the heavy hole (HH) level and the light hole (LH) level. In addition, below the graph of each figure, a table showing the combination of the Al composition ratio and the In composition ratio used in the calculation and the lattice mismatch corresponding to each combination is added. In Figures 16-18 , the relationship in the case where different n-side first barrier layers 14a and p-side barrier layers 14f are adopted is shown. In Figure 16 , the relationship in the case where Al 0.24 Ga 0.76 As and Al 0.35 Ga 0.55 In 0.1 As are adopted as the n-side first barrier layer 14a and the p-side barrier layer 14f, respectively, is shown. In Figure 17 , the relationship in the case where Al 0.27 Ga 0.73 As and Al 0.37 Ga 0.53 In​0.1 The relationship in the case of As. In Figure 18 it shows that Al 0.3 Ga 0.7 As and Al 0.4 Ga 0.5 In 0.1 As are respectively adopted as the n-side first barrier layer 14a and the p-side barrier layer 14f. In addition, as the well layer 14d, a quaternary semiconductor material film of the AlGaInAs type is adopted.

[0176] In the present embodiment, since the substrate 10 of the semiconductor light-emitting element 1 is a GaAs substrate, when a quaternary semiconductor material of the AlGaInAs type is adopted as each of the barrier layers and the well layer 14d, a compressive strain can be generated in the well layer 14d. When the well layer 14d has a compressive strain, by adjusting the composition of the well layer 14d, the number of light holes formed in the valence band of the well layer 14d can be reduced. Therefore, the recombination probability between the light holes and the electrons can be reduced, and thus the polarization ratio of the output light from the semiconductor light-emitting element can be increased.

[0177] As Figures 16-18 shown in each of the tables, by increasing the Al composition ratio of the well layer 14d, the lattice mismatch of the well layer 14d, that is, the compressive strain of the well layer 14d can be increased. Thus, as Figures 16-18 shown in each of the curves, the energy difference between the lowest energy level (HH1) of the heavy holes and the lowest energy level (LH1) of the light holes can be increased. For example, if the composition of the well layer 14d is expressed as Al yw Ga 1-xw-yw In xw As as described above, the relationship of 0 < yw < 1 and 0 < xw < 1 can be established. In this way, since the well layer 14d contains Al, when the well layer 14d has a 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 holes and the electrons can be reduced, and thus 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.

[0178] In Figures 16-18 the example shown, the Al composition ratio of the well layer 14d can also be set to an Al composition ratio such that higher-order light hole energy levels ( Figure 17 and Figure 18 LH2, etc. shown) other than the lowest energy level (LH1) of the light holes do not appear. For example, in Figure 16 the example shown, the Al composition ratio can be 0 or more, and in Figure 17 the example shown, the Al composition ratio can be about 0.005 or more, and in Figure 18In the example shown, the Al component ratio should be around 0.03 or higher. Figures 16-18 As shown, the region where the Al component ratio does not form higher-order light hole energy levels other than the lowest energy level (LH1) is defined as the component ratio setting region.

[0179] 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.

[0180] [1-3. Variation Example 1]

[0181] Next, the semiconductor light-emitting element of Modification 1 of this embodiment is used... Figures 19-21 Please provide an explanation. Figure 19 This is a schematic diagram showing the general outline of the band structure of the semiconductor light-emitting element 1a in this modified example. Figure 20 This is a schematic diagram showing the energy differences ΔEc2 and ΔEv2 between 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 in this modified example. Figure 21 This is a graph showing the relationship between the Al composition ratio of the p-side barrier layer 14f in this modified example and the energy differences ΔEc2 and ΔEv2.

[0182] like Figure 19 As shown, the semiconductor light-emitting element 1a of this modified example further includes a p-side guiding layer 14g disposed between the p-side barrier layer 14f and the p-type cladding layer 17, and having a refractive index greater than that of the p-type cladding layer 17. In this modified example, the p-side guiding layer 14g is an Al film with a thickness of 30 nm. 0.27 Ga 0.73 As a film. The semiconductor light-emitting element 1a has such a p-side guiding layer 14g, which enables high-precision control of the light distribution in the vertical direction and suppresses excessive bias of the light distribution towards the n-type semiconductor layer side (i.e., the n-type cladding 12 side). Therefore, it is possible to suppress the decrease in the light confinement coefficient in the vertical direction towards the well layer 14d and the increase in the working carrier density within the well layer 14d. That is, it is possible to suppress the degradation of the temperature characteristics of the semiconductor light-emitting element 1a. Furthermore, if the p-side guiding layer 14g is undoped, it is possible to suppress the increase in free carrier loss caused by impurity doping, thus achieving low loss in the waveguide. As a result, a semiconductor laser element with excellent temperature characteristics and high slope efficiency can be realized.

[0183] In addition, such as Figure 20 As shown, if the energy differences between the conduction band potential energy and the valence band potential energy between the p-side barrier layer 14f and the p-side guiding layer 14g are expressed as ΔEc2 and ΔEv2, respectively, then the relationship between the Al component ratio of the p-side barrier layer 14f and the energy differences ΔEc2 and ΔEv2 becomes: Figure 21 As shown in the curve graph. Here, the p-side guiding layer 14g is composed of Al.0.3 Ga 0.7 As, the In composition ratio of the p-side barrier layer 14f is fixed at 0.1.

[0184] In order to sufficiently increase the refractive index of the p-side guide layer 14g while suppressing the generation of electrons leaking from the well layer 14d to the p-side guide layer 14g, the energy difference ΔEc2 of the conduction band potential energy can also be 40 meV or more. In this case, as shown in FIG. 8, the Al composition ratio of the p-side barrier layer 14f can be 0.38 or more. Further, in order to suppress the increase in the operating voltage of the semiconductor light emitting element la by suppressing the energy required for the supply of holes to the well layer 14d, the energy difference ΔEv2 can also be 30 meV or less. In this case, as shown in FIG. 9, the Al composition ratio of the p-side barrier layer 14f can be 0.48 or less. Figure 21 Figure 21

[0185] Further, the same as 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 used. Figures 9-11 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 is determined. If the Al composition ratio of the p-side guide layer 14g is set to ygp1, the composition of the p-side guide layer 14g is Al ygp1 Ga 1-ygp1 As indicates that if the Al composition ratio and the In composition ratio of the p-side barrier layer 14f are set to ybp1 and xbp1, respectively,

[0186] ybp1 < xbp1 + 0.975 ygp1 + 0.069,

[0187] ybp1 > 0.4 xbp1 + 0.975 ygp1 + 0.029, and

[0188] 0.2 < ygp1 < 0.4 can be established.

[0189] The p-side guide layer 14g having such a composition is substantially lattice-matched to the substrate 10 composed of a GaAs substrate. Thereby, the film thickness of the p-side barrier layer 14f having a compressive lattice mismatch can be made to be equal to or less than the critical film thickness. Thus, the decrease in the crystallinity of the p-side barrier layer 14f can be suppressed.

[0190] ​​Furthermore, when the well layer 14d is a quaternary semiconductor material film containing Al, the compressive strain of the active layer 14 increases. Therefore, by disposing the p-side guiding layer 14g, which is approximately lattice-matched to the GaAs substrate, above the p-side barrier layer 14f, the accumulation of compressive strain near the active layer 14 can be suppressed. In addition, in this case, the potential energy between the lowest energy levels of heavy holes and light holes increases, thus reducing the recombination probability of light holes and electrons. Consequently, the TM polarization component caused by the recombination of light holes and electrons can be reduced, thus improving the polarization ratio.

[0191] Furthermore, by establishing the above relationship, the energy difference ΔEv2 of the valence band potential between the p-side barrier layer 14f and the p-side guiding layer 14g can be suppressed to below 30meV, and the energy difference ΔEc2 of the conduction band potential can be increased to above 25meV. Therefore, it is possible to suppress the increase of the working voltage while suppressing the leakage of electrons from the well layer.

[0192] Furthermore, by setting the Al composition ratio ygp1 of the p-side guiding layer 14g to above 0.2 and below 0.4, the light distribution in the vertical direction can be controlled with higher precision, and the waveguide can be made less lossy while suppressing a significant decrease in the optical confinement coefficient.

[0193] [1-4. Variation Example 2]

[0194] Next, use Figure 22 The semiconductor light-emitting element of Modification 2 of this embodiment will be described. Figure 22 This is a schematic diagram showing the general outline of the band structure of the semiconductor light-emitting element 1b in this modified example.

[0195] like Figure 22 As shown, the semiconductor light-emitting element 1b of this modified example, in addition to the constituent elements of the semiconductor light-emitting element 1a of modified example 1, also includes a p-side intermediate layer 14e. 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 modified example, the p-side intermediate layer 14e is an Al film with a thickness of 3 nm. 0.27 Ga 0.73 As membrane. The p-side intermediate layer 14e is a relatively thin layer, thin enough that electrons supplied to the well layer 14d can permeate to the p-side barrier layer 14f.

[0196] If we assume the Al component ratio of the p-side intermediate layer 14e is ykp1, then the composition of the p-side intermediate layer 14e consists of Al ykp1 Ga 1- ykp1 As indicates that if the Al and In composition ratios of the p-side barrier layer 14f are set to ybp1 and xbp1 respectively, then

[0197] ybp1≦xbp1+0.975ykp1+0.069,

[0198] ybp1≧0.4xbp1+0.975ykp1+0.029, and

[0199] The relationship of 0.2≦ykp1≦0.4 can be established.

[0200] When referring to Figures 9-11 , in a case where the above relationship is established with respect to the Al composition ratio ybp1 of the p-side barrier layer 14f, the energy difference ΔEc2 of the conduction band potential between the p-side barrier layer 14f and the p-side intermediate layer 14e is 25 meV or more, and the energy difference ΔEv2 of the valence band potential is 30 meV or less. Thus, it is possible to suppress a situation in which the injection of holes into the well layer 14d is hindered, so it is possible to suppress an increase in operating voltage. In addition, it is possible to suppress the overflow of electrons from the well layer 14d.

[0201] Further, by setting the Al composition ratio of the p-side intermediate layer 14e to 0.2 or more and 0.4 or less, it is possible to control the light distribution in the vertical direction with higher precision, and it is possible to realize a low-loss waveguide while increasing the light confinement coefficient.

[0202] Further, by disposing the p-side intermediate layer 14e composed of an AlGaAs layer, which is substantially lattice-matched to the GaAs substrate, between the well layer 14d and the p-side barrier layer 14f, it is possible to disperse the formation region of the compressive strain in the vicinity of the active layer 14, so it is possible to suppress a decrease in crystallinity due to the concentration of the compressive strain.

[0203] Further, since it is possible to reduce the energy difference of the valence band potential between the well layer 14d and the p-side intermediate layer 14e, it is possible to suppress the formation of light holes of a high-order energy level. Thus, it is possible to suppress a decrease in the polarization ratio.

[0204] [1-5. Modification 3]

[0205] Next, a semiconductor light emitting element of Modification 3 of the present embodiment will be described. Figure 23 A semiconductor light emitting element of Modification 3 of the present embodiment will be described. Figure 23 is a schematic view that schematically shows the band structure of the semiconductor light emitting element 1c of the present modification.

[0206] As shown in Figure 23 , the semiconductor light emitting element 1c of the present modification has an n-side second barrier layer 14b in addition to the constituent elements of the semiconductor light emitting element 1a of Modification 1. 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 the present modification, the n-side second barrier layer 14b is an Al0.3Ga0.7As layer having a film thickness of 7 nm. 0.31 Ga 0.66 In 0.03As membrane.

[0207] If the Al and In component ratios of the second barrier layer 14b on the n-side are set to ybn2 and xbn2 respectively, then the composition of the second barrier layer 14b on the n-side will change from Al... ybn2 Ga 1-xbn2-ybn2 In xbn2 As indicates,

[0208] ybn2≧xbn2+ybn1,

[0209] ybn2≦0.4xbn2+0.975ybn1+0.061,

[0210] xbn2≦0.15, and

[0211] The relationship 0.2≦ybn1≦0.35 holds true.

[0212] When the above relationship holds regarding 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 first barrier layer 14a and the n-side second barrier layer 14b is less than 50 meV, and the energy difference ΔEv2 of the valence band potential energy is more than 30 meV. Therefore, it is possible to suppress the situation that hinders the injection of electrons into the well layer 14d, and thus suppress the increase in operating voltage. Furthermore, it is possible to suppress the overflow of holes from the well layer 14d.

[0213] Furthermore, by setting the Al composition ratio of the n-side first barrier layer 14a to a low level, specifically between 0.2 and 0.35, the refractive index of the n-side first barrier layer 14a can be increased, making it easier to direct the vertical light distribution closer to the n-type semiconductor layer side. Consequently, reducing the waveguide's loss becomes easier.

[0214] [1-6. Variation Example 4]

[0215] Next, use Figure 24 The semiconductor light-emitting element of Modification 4 of this embodiment will be described. Figure 24 This is a schematic diagram showing the general outline of the band structure of the semiconductor light-emitting element 1d in this modified example.

[0216] like Figure 24 As shown, the semiconductor light-emitting element 1d of this modified example, in addition to the constituent elements of the semiconductor light-emitting element 1c of modified example 3, also includes a p-side intermediate layer 14e and an n-side third barrier layer 14c. 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 modified example, the n-side third barrier layer 14c is an Al film with a thickness of 3 nm. 0.27 Ga 0.73As a film. The n-side third barrier layer 14c is a thin layer, thin to the extent that electrons supplied to the well layer 14d seep out to the n-side second barrier layer 14b side.

[0217] If 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 As a film. Here, it can be that, if the Al composition ratio and the In composition ratio of the n-side second barrier layer 14b are set to ybn2 and xbn2, respectively,

[0218] ybn2≧xbn2+ybn3,

[0219] ybn2≦0.4xbn2+0.975ybn3+0.061, and

[0220] 0.2≦ybn3≦0.35.

[0221] In the case where the above relationship holds with respect to 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. Further, by making the Al composition ratio of the n-side third barrier layer 14c 0.35 or less, the band gap energy of the n-side third barrier layer 14c can be reduced. Thus, the case where electrons are prevented from being injected into the well layer 14d can be suppressed, so the increase in the operating voltage can be suppressed.

[0222] Further, in the case where the above relationship holds with respect to the Al composition ratio ybn2 of the n-side second barrier layer 14b, the energy difference ΔEv2 of 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. Thus, the overflow of holes from the well layer 14d can be suppressed.

[0223] Further, by making the Al composition ratio of the n-side third barrier layer 14c low and 0.2 or more and 0.35 or less, the refractive index of the n-side third barrier layer 14c can be increased, so the light distribution in the vertical direction can be easily made closer to the n-type semiconductor layer side. Thus, the low loss of the waveguide becomes easy.

[0224] [1-7. Modification 5]

[0225] Next, the semiconductor light emitting element of Modification 5 of the present embodiment will be described. Figure 25 The semiconductor light emitting element of Modification 5 of the present embodiment will be described. Figure 25 is a schematic diagram showing an outline of the band structure of the semiconductor light emitting element 1e of the present modification.

[0226] As Figure 25As shown, the semiconductor light emitting element 1e of the present modification example has a multiple quantum well structure. The active layer of the semiconductor light emitting element 1e has the n-side first barrier layer 14a, the first intermediate barrier layer 14h, the p-side barrier layer 14f, and two layers of the well layer 14d.

[0227] 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 the present modification example, the first intermediate barrier layer 14h is an Al 0.3 Ga 0.7 As film.

[0228] One of the two layers of the well layer 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 layers of the well layer 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 the present modification example, the two well layers 14d are Al 0.08 Ga 0.67 In 0.25 As films, respectively.

[0229] In the semiconductor light emitting element 1e having the multiple quantum well structure like the present modification example, it is also possible to suppress the overflow of electrons in the p-side barrier layer 14f while suppressing the increase in the operating voltage.

[0230] Further, the two layers of the well layer 14d are provided in the semiconductor light emitting element 1e of the present modification example, but the number of layers of the well layer 14d is not limited to two. The number of layers of the well layer 14d can be three or more. In the case where the semiconductor light emitting element 1e has N layers (N is an integer of two or more) of the well layer 14d, the semiconductor light emitting element 1e has (N-1) layers of the intermediate barrier layer from the first intermediate barrier layer to the (N-1)th intermediate barrier layer. Here, if the Al composition ratio and the In composition ratio of the kth intermediate barrier layer (k = 1, 2, 3,..., N-1) are denoted by ybk and xbk (k = 1, 2, 3,..., N-1), respectively, the composition of the kth intermediate barrier layer is expressed as Al ybk Ga 1-xbk-ybk In xbk As. Here,

[0231] the relationships ybn1≦ybk≦ybp1 and xbn1≦xbk≦xbp1 are satisfied, and the band gap energy of the kth intermediate barrier layer is equal to or higher than the band gap energy of the n-side first barrier layer 14a and equal to or lower than the band gap energy of the p-side barrier layer 14f.

[0232] the relationships ybn1≦ybk≦ybp1 and xbn1≦xbk≦xbp1 are satisfied, and the band gap energy of the kth intermediate barrier layer is equal to or higher than the band gap energy of the n-side first barrier layer 14a and equal to or lower than the band gap energy of the p-side barrier layer 14f.

[0233] Thus, the same effects as the semiconductor light emitting element 1 of the present embodiment can be obtained. Further, by adopting the multiple quantum well structure, the operating carrier density in the laser oscillation state of each well layer can be reduced, so the overflow of electrons can be further suppressed. Thus, the temperature characteristics of the semiconductor light emitting element 1e are further improved.

[0234] [1-8. Modification 6]

[0235] Next, the semiconductor light emitting element of Modification 6 of the present embodiment will be described. Figure 26 The semiconductor light emitting element of Modification 6 of the present embodiment will be described. Figure 26 is a schematic diagram showing an outline of the band structure of the semiconductor light emitting element 1f of the present modification.

[0236] As Figure 26 indicated, the semiconductor light emitting element 1f of the present modification has a multiple quantum well structure. The active layer of the semiconductor light emitting element 1f has the n-side first barrier layer 14a, the first intermediate barrier layer 14ha, the p-side barrier layer 14f, and two layers of well layers 14d.

[0237] The first intermediate barrier layer 14ha of the present modification, like the first intermediate barrier layer 14h of Modification 5, is a barrier layer disposed between the n-side first barrier layer 14a and the p-side barrier layer 14f. In the present 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.

[0238] The first intermediate n-side barrier layer 14i is a layer of the first intermediate barrier layer 14ha disposed on the n-side first barrier layer 14a side. In the present modification, the first intermediate n-side barrier layer 14i is an Al 0.3 Ga 0.7 As film.

[0239] The first intermediate p-side barrier layer 14j is a layer of the first intermediate barrier layer 14ha disposed on the p-side barrier layer 14f side. In the present modification, the first intermediate p-side barrier layer 14j is an Al 0.45 Ga 0.45 In 0.1 As film.

[0240] One of the two layers of 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 layers of 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 the present modification, the two well layers 14d are each an Al 0.08 Ga 0.67 In 0.25 As film.

[0241] In the semiconductor light emitting element 1f having the multiple quantum well structure as in the present modification example, the overflow of electrons in the p-side barrier layer 14f can be suppressed while suppressing an increase in the operating voltage.

[0242] In addition, the two layers of the well layer 14d are provided in the semiconductor light emitting element 1f of the present modification example, but the number of layers of the well layer 14d is not limited to two. The number of layers of the well layer 14d can be three or more. In the case where the semiconductor light emitting element 1f has the N layers (N is an integer of two or more) of the well layer 14d, the semiconductor light emitting element 1f has (N-1) layers of the intermediate barrier layer from the first intermediate barrier layer to the (N-1)th intermediate barrier layer. Further, the kth intermediate barrier layer (k = 1, 2, 3,..., N-1) has 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 included in the kth intermediate barrier layer (k = 1, 2, 3,..., N-1) are set as ybckand 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 set as ybkand 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 represented as Al ybck Ga 1-xbck-ybck In xbck As and Al ybk Ga 1-xbk- ybk In xbk As. Here,

[0243] ybn1≦ybk≦ybp1,

[0244] xbn1≦xbk≦xbp1, and

[0245] the relationship of ybn1≦ybk≦ybp1is established, and the band gap energy of the kth intermediate n-side barrier layer is lower than or equal to 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 lower than or equal to the band gap energy of the p-side barrier layer 14f.

[0246] Thus, the same effects as the semiconductor light emitting element 1e of the modification example 5 can be obtained.

[0247] Further, it can be that

[0248] ybp1≦xbp1+0.975ybck+0.069

[0249] ybp1≧0.4xbp1+0.975ybck+0.029

[0250] the relationship of 0.2≦ybck≦0.4 is established.

[0251] Thus, the increase in the valence band potential difference between the kth intermediate n-side barrier layer and the kth intermediate p-side barrier layer can be suppressed by the kth intermediate barrier layer, and the conduction band potential of the kth intermediate p-side barrier layer can be made larger than that of the kth intermediate n-side barrier layer. Thus, the overflow of electrons from each well layer 14d can be suppressed without impairing the hole conductivity between the two adjacent well layers 14d.

[0252] 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 Modification Example 5 can be obtained, and by adopting the multiple quantum well structure of this modification example, not only can the operating carrier density in the laser oscillation state of the well layer 14d be reduced, but also the suppression of electron overflow and the improvement of temperature characteristics can be achieved.

[0253] [1-9. Modification Example 7]

[0254] Next, the semiconductor light emitting element of Modification Example 7 of the present embodiment will be described. Figure 27 The semiconductor light emitting element of Modification Example 7 of the present embodiment will be described. Figure 27 is a cross-sectional view showing the structure of the light exit end surface portion 40 of the semiconductor light emitting element 1g of the present modification example. In Figure 27 , a part of the cross section of the semiconductor light emitting element 1g of the present modification example parallel to the resonance direction of the laser and perpendicular to the main surface of the substrate 10 is shown.

[0255] The semiconductor light emitting element 1g of the present modification example is different from the semiconductor light emitting element 1 of Embodiment 1 in that it has a so-called end surface window structure in the light exit end surface portion 40, and is otherwise identical. In Figure 27 , the n-side electrode 31 and the p-side electrode 32 are omitted. In addition, the light exit end surface portion 40 is a region including the light exit end surface 1F of the semiconductor light emitting element 1g. In addition, the semiconductor light emitting element 1g can have an end surface window structure not only in the light exit end surface portion 40 but also in the rear end surface portion (i.e., a region including the end surface on the opposite side of the light exit end surface 1F). The region occupied by the rear end surface portion is not particularly limited, and for example, at least includes a region having a length of 1% of the resonator length in the resonance direction from the rear end surface.

[0256] Specifically, in the light exit end surface portion 40 of the active layer 14 of the semiconductor light emitting element 1g of the present modification example, vacancies or impurities are diffused. Hereinafter, the end surface window structure of the present modification example will be described in detail.

[0257] InAs has the largest lattice constant and the smallest band gap energy among AlAs, GaAs, and InAs. In the case where the desired band gap energy is obtained by using a quaternary semiconductor material of the AlGaInAs type for the well layer 14d and each barrier layer as in the semiconductor light emitting element lg of this modification example, the In content of the well layer composed of AlGaInAs is increased compared to the case where the desired band gap energy is obtained by using a semiconductor material composed of InGaAs for the well layer, and thus the compressive strain of the well layer becomes larger.

[0258] According to the above, in the configuration where a quaternary semiconductor material of the AlGaInAs type is used for the well layer 14d and each barrier layer, in the case where vacancies or impurities are diffused to the light emission end surface portion 40 of the semiconductor light emitting element, the strain energy of the well layer 14d becomes small, and thus the In atoms of the well layer 14d easily exchange with the Al atoms and Ga atoms present at the lattice positions of Group III with respect to the stacking direction. Thus, the band gap energy of the well layer 14d easily becomes large.

[0259] As a result, the band gap energy of the well layer at the light emission end surface portion 40 where the optical density is large becomes large, and a so-called window configuration can be formed. That is, the band gap energy of the portion of the active layer 14 where the end surface window configuration is formed becomes large compared to the band gap energy of the portion of the active layer 14 where the end surface window configuration is not formed. Thus, even if the band gap energy of the light emission end surface portion 40 becomes small due to heat generation, it is possible to maintain a state where the light absorption of the well layer 14d of the light emission end surface portion 40 is small. Thus, it is possible to suppress the occurrence of COD due to the absorption of light by the light emission end surface portion 40.

[0260] If the length of the window configuration in the resonator direction is Lw, the distance between the resonator end surface and the region (gain region) that is not the window configuration becomes long when Lw is long. The gain region is a region where light emission occurs in the active layer 14. By current injection to the gain region, light emission recombination and non-light emission recombination occur in the active layer 14.

[0261] The temperature of the active layer 14 rises not only by Joule heating of the series resistance component included in the semiconductor light emitting element lg, but also by heat generation accompanying non-light emission recombination. The resonator end surface is easily produced to have crystal defect levels because it is formed by cleaving when the resonator is manufactured. When the semiconductor light emitting element lg, the band gap energy of the resonator end surface becomes further small, and thus the light absorption under the crystal defect levels at the resonator end surface becomes larger, and COD easily occurs.

[0262] If Lw is made longer, the gain region is farther from the resonator facet, and the effect of heat generation in the gain region on the resonator facet becomes smaller, which is advantageous for suppressing the occurrence of COD. However, if Lw is too long, the current concentration to the gain region becomes larger because the length of the gain region becomes shorter. Consequently, the overflow of electrons from the active layer 14 increases, and the temperature characteristics deteriorate.

[0263] In this regard, in the case where the well layer 14d and each barrier layer are made of quaternary semiconductor material of the AlGaInAs type as described above, the In atoms of the well layer 14d are likely to exchange with the Al atoms and Ga atoms present at the lattice positions of Group III with respect to the stacking direction, and the band gap energy of the well layer 14d is likely to increase. In the case where the band gap energy of the active layer 14 in the window structure region increases, the light absorption of the laser in the window structure region decreases, and the heat generation in the window structure region also decreases. Therefore, in the semiconductor light emitting element 1g of the present modified example, even if Lw is made shorter, the effect of heat generation in the gain region on the resonator facet can be reduced, and Lw can be shortened compared to the conventional configuration in which the well layer 14d is made of InGaAs and each barrier layer is made of AlGaAs. Specifically, Lw needs to be 30 μm or more in the conventional configuration, but if the well layer 14d and each barrier layer are made of quaternary semiconductor material of the AlGaInAs type, COD can be suppressed even if Lw is 15 μm or more.

[0264] Further, if 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 the case where the window structure is formed by impurity diffusion, and thus the decrease in the slope efficiency can be suppressed.

[0265] (Embodiment 2)

[0266] The semiconductor light emitting element of Embodiment 2 will be described. The semiconductor light emitting element of the present embodiment differs from the semiconductor light emitting element 1 of Embodiment 1 in that it further includes an n-side guide layer and the like between the active layer 14 and the n-type cladding layer. Hereinafter, the semiconductor light emitting element of the present embodiment will be described with the focus on the points of difference from the semiconductor light emitting element 1 of Embodiment 1, using the same reference numerals as in Embodiment 1. Figure 28

[0267] Figure 28 is a schematic cross-sectional view showing the overall structure of the semiconductor light emitting element 101 of the present embodiment. As shown in Figure 28 The semiconductor light emitting element 101 of the present embodiment further 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 constituent elements of the semiconductor light emitting element 1 of Embodiment 1.

[0268] ​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 refractive index of the n-side guide layer 13 is larger than that of the n-type cladding layer 12. Thus, as compared with the semiconductor light emitting element 1 of Embodiment 1, it is possible to dispose the light distribution in the vertical direction closer to the active layer 14. Thus, it is possible to suppress the decrease in the light confinement coefficient to the active layer 14. In the present embodiment, the refractive index of the n-side guide layer 13 is increased by making the Al composition ratio of the n-side guide layer 13 lower than the Al composition ratio of the n-type cladding layer 12. Further, the n-side guide layer 13 contains an impurity of n-type, 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 of the n-side guide layer 13 on the active layer 14 side. Thus, it is possible to suppress the impairment of the electrical conductivity of the n-side guide layer 13, and to reduce the waveguide loss caused by the impurity in the n-side guide layer 13. Specifically, the n-side guide layer 13 is an Al 0.27 Ga 0.73 As layer having a film thickness of 1 μm. Further, in the n-side guide layer 13, the region on the active layer 14 side having a film thickness of 0.25 μm is doped with Si at a concentration of 5 x 10 17 cm -3 -2, and the region on the n-type cladding layer 12 side having a film thickness of 0.75 μm is doped with Si at a concentration of 5 x 10 16 cm -3 -2. The impurity concentration of the n-side guide layer 13 is not particularly limited, and in order to reduce the waveguide loss of the n-side guide layer 13, the impurity concentration of the region on the n-type cladding layer 12 side in the n-side guide layer 13 can be set to, for example, 1 x 10 17 cm -3 -4 or less. Further, the impurity concentration of the region on the active layer 14 side in the n-side guide layer 13 can be made, for example, higher than 1 x 10 17 cm -3 -4, so as not to impair the electrical conductivity of the n-side guide layer 13.

[0269] 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 the present embodiment, the first strain control layer 15 is an Al 0.70 Ga 0.30 As layer having a film thickness of 0.05 μm.

[0270] 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 the present embodiment, the second strain control layer 16 is an Al 0.30 Ga 0.70 As layer having a film thickness of 0.16 μm.

[0271] The impurity concentration of the first strain control layer 15 and the second strain control layer 16 is, for example, 2 x 1017 cm -3 above, 6 x 10 17 cm -3 below. In the present embodiment, C is doped in the first strain control layer 15 and the second strain control layer 16 at a concentration of 3 x 10 17 cm -3 .

[0272] 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 in the case where the semiconductor light emitting element 101 is mounted junction down (i.e., in the case where the p-side electrode 32 is connected to the mounting surface). In the semiconductor light emitting element 101 of the present embodiment, in the case of junction down mounting, most of the stress caused by mounting strain is absorbed by the second strain control layer 16, which has a small Young's modulus. Therefore, the stress caused by mounting strain can be suppressed from acting on the active layer 14, which is disposed at a position farther from the mounting surface than the second strain control layer 16. Thus, the strain in the active layer 14 can be stabilized to the magnitude of the strain determined in crystal growth. As a result, the controllability of the band structure after mounting the semiconductor light emitting element 101 is improved, so stable high-temperature high-output operation can be performed. Thus, according to the present embodiment, a semiconductor laser element that is excellent in temperature characteristics, has a high slope efficiency, and is suitable for high-temperature high-output operation can be stably realized.

[0273] (Embodiment 3)

[0274] The semiconductor light emitting element of Embodiment 3 will be described. The semiconductor light emitting element of the present embodiment differs from the semiconductor light emitting element 101 of Embodiment 2 in that the p-type semiconductor layer has a protrusion. Hereinafter, the semiconductor light emitting element of the present embodiment will be described, focusing on the difference from the semiconductor light emitting element 101 of Embodiment 2. Figure 29

[0275] Figure 29 is a schematic cross-sectional view showing the overall structure of the semiconductor light emitting element 201 of the present embodiment. As shown in Figure 29 , the semiconductor light emitting element 201 of the present embodiment includes a substrate 10, a buffer layer 11, an n-clad layer 12, an n-guide layer 13, an active layer 14, a first strain control layer 15, a second strain control layer 16, a p-clad layer 17, a contact layer 218, a current blocking layer 20, an n-side electrode 31, and a p-side electrode 32.

[0276] ​The contact layer 218 of this embodiment has the same composition as the contact layer 18 of Embodiment 2, but differs from the contact layer 18 of Embodiment 2 in that it has a ridge portion 218r. On the upper surface of the contact layer 218 (i.e., the surface on the p-side electrode 32 side), two grooves 218t extending in the resonance direction of the laser are formed, and a ridge portion 218r is formed between the two grooves 218t. In this embodiment, the current is concentrated in the ridge portion 218r, and a waveguide is formed along the ridge portion 218r.

[0277] The current blocking layer 20 is an insulating layer for concentrating the current in the ridge portion 218r. The current blocking layer 20 is disposed in the region of the contact layer 218 other than the ridge portion 218r. In this embodiment, the current blocking layer 20 is disposed in the region of the upper surface of the contact layer 218 other than the ridge portion 218r. In other words, in the current blocking layer 20, a slit extending in the resonance direction of the laser is formed on the ridge portion 218r. The current blocking layer 20 is an insulating film, and is not particularly limited, and in this embodiment is a SiO2 film having a film thickness of 0.02 μm.

[0278] Next, the use of the semiconductor light emitting element 201 of this embodiment will be described. Figures 30-32 The operation and effects of the semiconductor light emitting element 201 of this embodiment will be described. Figure 30 is a schematic cross-sectional view showing the dimensions of each part of the semiconductor light emitting element 201 of this embodiment. Figure 31 is a schematic cross-sectional view showing the mounting state of the semiconductor light emitting element 201 of this embodiment. Figure 32 is a graph showing the distribution of the shear stress σxy corresponding to the position in the x-axis direction of the active layer 14 of the semiconductor light emitting element 201 of this embodiment.

[0279] As shown in Figure 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 assumed to be the y-axis direction. Furthermore, the direction perpendicular to the resonance direction of the laser and the y-axis direction is assumed to be the x-axis direction. Furthermore, as shown in Figure 30 , the width of each of the two grooves 218t in the x-axis direction is assumed to be d1, and the width of the ridge portion 218r in the x-axis direction is assumed to be Wr. Furthermore, the width of the semiconductor light emitting element 201 in the x-axis direction is assumed to be Wc.

[0280] The stress acting on the semiconductor light emitting element 201 when such a semiconductor light emitting element 201 is mounted with the junction facing down in the sub-assembly 202 as shown in Figure 31 will be described.

[0281] The sub-assembly 202 is, for example, a plate-shaped member formed of Cu.

[0282] Here, the coefficient of thermal expansion of the semiconductor light-emitting element 201 is the same as that of GaAs (5.35 × 10⁻⁶). -6 K -1 The coefficient of thermal expansion is similar to that of subassembly 202, but less than that of subassembly 202 (16.8 × 10⁻⁶). -6 K -1 When the semiconductor light-emitting element 201 is mounted with its junction facing downwards on such a sub-assembly 202, the shear stress corresponding to the difference in the coefficients of thermal expansion between the semiconductor light-emitting element 201 and the sub-assembly 202 acts on the active layer 14 of the semiconductor light-emitting element 201. In this case, the semiconductor light-emitting element 201 is subjected to compressive stress in the x-axis direction from the sub-assembly 202. Specifically, as... Figure 31 As shown, clockwise shear stress σ1R and counterclockwise shear stress σ1L act on the right and left ends of the semiconductor light-emitting element 201 along the x-axis, respectively. Furthermore, counterclockwise shear stress σ2R and clockwise shear stress σ2L act on the right and left ends of the raised portion 218r, respectively. Thus, the semiconductor light-emitting element 201 experiences shear stresses that are centrally symmetrical with respect to the x-axis direction of the raised portion 218r.

[0283] Here, using Figure 31 and Figure 32 The shear stress acting on the semiconductor light-emitting element 201 is explained. Figure 32 The diagram 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 protrusion 218r in the x-axis direction is 200 μm. Additionally, in... Figure 32 The table shows the calculation results for the width d1 of the groove 218t being 20μm, 40μm, and 80μm. Furthermore, in... Figure 32 The calculation results of the shear stress without the groove 218t are also presented.

[0284] like Figure 31 As shown, for example, at the right end of the raised portion 218r in the x-axis direction, the shear stress σ2R caused by the groove 218t and the shear stress σ1R caused by the right end of the semiconductor light-emitting element 201 in the x-axis direction are oriented in opposite directions, thus the shear stress is weakened (see reference). Figure 32 (The point at position x is 100 μm). At the left end of the 218r ridge along the x-axis, similarly to the right end, the shear stress weakens (refer to...). Figure 32 (The point with a position x of -100μm).

[0285] In the semiconductor light-emitting element 201, such as in Figure 30As shown by the thick dashed arrow, current diffuses from the protrusion 218r along the x-axis direction to the active layer 14. Therefore, the laser light in the semiconductor light-emitting element 201 is affected by the shear stress of the groove 218t because it is distributed throughout the active layer 14 to the region corresponding to the position of the groove 218t along the x-axis. Furthermore, Figure 30 The dashed ellipse shown represents the outer edge of the laser distribution area. Furthermore, if the distribution of shear stress in the active layer 14 is not perfectly antisymmetric relative to the center of the x-axis direction of the protrusion 218r, then when birefringence is generated in the semiconductor light-emitting element 201 due to shear stress, the polarization surface is tilted because the integral of the correlation between light distribution and shear stress is no longer 0. The integral of the correlation between shear stress and light distribution is expressed by the following formula.

[0286] [Formula 1]

[0287] ∫∫σ xy |Φ| 2 dxdy |Φ| 2 Light distribution

[0288] In this embodiment, by forming the groove 218t, the shear stress at the x-axis end of the protrusion 218r can be reduced, thus suppressing the influence of shear stress on light distribution. Therefore, in the semiconductor light-emitting element 201 according to this embodiment, the situation where the polarizing surface tilts and the polarization ratio decreases due to asymmetric strain relative to the center of the x-axis direction occurs in the semiconductor light-emitting element 201 can be suppressed. For example, by making the width d1 of the groove 218t in the x-axis direction 10 μm or more, the shear stress near the x-axis end of the protrusion 218r can be weakened. On the other hand, if the width d1 of the groove 218t is too wide, the load will be concentrated on the protrusion 218r when the junction is mounted downwards, so the width d1 of the groove 218t can be set to 40 μm or less.

[0289] Furthermore, regarding the depth of the groove 218t, if the stepped portion of the groove 218t (i.e., the portion where the bottom surface of the groove 218t connects to the side surface) is too close to the active layer 14, the shear stress generated in the active layer 14 due to its unevenness will increase, and the polarization ratio will decrease. Therefore, the depth of the groove 218t can 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.

[0290] (Implementation Method 4)

[0291] The semiconductor light-emitting element of Embodiment 4 and its manufacturing method will be described. The semiconductor light-emitting element of this embodiment differs from the semiconductor light-emitting element 1c of Modification 3 of Embodiment 1 mainly in the materials used for the p-side guiding layer, the n-type cladding layer, and the p-type cladding layer. Hereinafter, the semiconductor light-emitting element of this embodiment will be described focusing on the differences from the semiconductor light-emitting element 1c of Modification 3 of Embodiment 1.

[0292] [4-1. Overall Structure]

[0293] First, the overall structure of the semiconductor light-emitting element of this embodiment will be described. The semiconductor light-emitting element of this embodiment is similar to the semiconductor light-emitting element 1c of Variation 3 of Embodiment 1, comprising a substrate, an n-type cladding layer, an active layer, a p-type cladding layer, a current-restricting layer, a contact layer, an n-side electrode, and a p-side electrode. The semiconductor light-emitting element of this embodiment also includes an n-side guiding layer disposed between the n-type cladding layer and the active layer.

[0294] The semiconductor light-emitting element of this embodiment differs from that of semiconductor light-emitting element 1c mainly in the materials used for each layer. Hereinafter, the layers of the semiconductor light-emitting element of this embodiment that use materials different from those of the layers of semiconductor light-emitting element 1c, as well as the n-side guiding layer, will be described.

[0295] If the composition of the n-type cladding is assumed to be yn2, then the composition of the n-type cladding is determined by (Al... yn2 Ga 1-yn2 ) 0.5 In 0.5 P represents. Additionally, (Al) yn2 Ga 1-yn2 ) 0.5 In 0.5 The composition ratio of In in the record of P (and (Al) yn2 Ga 1-yn2 The component ratio of () refers to the component ratio within the range of 0.5 after rounding to the second decimal place. Similarly, other component ratios expressed as decimals are not limited to a single value; they refer to the component ratio within the range of decimals after rounding to the nearest decimal place. By setting the components of the n-type cladding as (Al)... yn2 Ga 1-yn2 ) 0.5 In 0.5 In the n-type cladding, vacancies or impurities such as Zn and Mg readily diffuse. Therefore, when forming an end-face window structure in a semiconductor light-emitting element by diffusing vacancies or impurities, the formation time can be reduced. Furthermore, the concentration of impurities used in impurity diffusion can be reduced, thus minimizing light absorption caused by impurities. Consequently, the decrease in the luminous efficiency of the semiconductor light-emitting element can be suppressed.

[0296] In addition, when the strain of the n-type cladding layer formed on the substrate made of n-type GaAs is 0.2% or less, and the composition ratio of Al is 0 or more and 0.6 or less, the composition ratio of In can be 0.45 or more and 0.513 or less. In this embodiment, the n-type cladding layer is an n-type (Al 0.14 Ga 0.86 ) 0.5 In 0.5 P layer with a thickness of 3.5 μm. The n-type cladding layer includes multiple portions doped with impurities at different concentrations. The n-type cladding layer includes, in order from the end face closer to the substrate, a portion with a thickness of 2.5 μm doped with Si at a concentration of 1×10 18 cm -3 , a portion with a thickness of 0.5 μm doped with Si at a concentration of 5×10 17 cm -3 , and a portion with a thickness of 0.5 μm doped with Si at a concentration of 2×10 17 cm -3 .

[0297] The n-side guiding layer is disposed between the n-type cladding layer and the active layer. In this embodiment, the n-side guiding layer is an n-type (Al 0.04 Ga 0.96 ) 0.5 In 0.5 P layer with a thickness of 0.5 μm. The n-side guiding layer is doped with Si at a concentration of 1×10 17 cm -3 .

[0298] The active layer has an n-side first barrier layer, an n-side second barrier layer, a well layer, a p-side barrier layer, and a p-side guiding layer. In this embodiment, the n-side first barrier layer is an undoped Al 0.5 Ga 0.5 As layer with a thickness of 14 nm. The n-side second barrier layer is an undoped Al 0.55 Ga 0.45 As layer with a thickness of 3.5 nm. The well layer is an undoped In 0.08 Ga 0.92 As layer with a thickness of 6 nm. The p-side barrier layer is an undoped Al<00​​​​​​​​​​​​​​​​​​1-gp2 ) 0.5 In 0.5 P, vacancies or impurities such as Zn and Mg easily diffuse in the p-side guiding layer. Thus, it has the same effect as the above-mentioned n-type cladding. In this embodiment, it is a p-type (Al 0.04 Ga 0.96 ) 0.5 In 0.5 P layer with a thickness of 220 nm. The p-side guiding layer is doped with C at a concentration of 1×10 17 cm -3 .

[0300] If the component ratio of Al in the p-type cladding is set as yp2, it is represented by (Al yp2 Ga 1-yp2 ) 0.5 In 0.5 P. By setting the component of the p-type cladding as (Al yp2 Ga 1-yp2 ) 0.5 In 0.5 P, vacancies or impurities such as Zn and Mg easily diffuse in the p-type cladding. Thus, it has the same effect as the above-mentioned n-type cladding. In this embodiment, the p-type cladding 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 cladding is doped with C at a concentration of 2×10 18 cm -3 .

[0301] Furthermore, in this embodiment, regarding the component ratio of Al in the n-type cladding yn2 and the component ratio of Al in the p-type cladding yp2, the relationship 0 < yn2 < yp2 < 1 holds. Thus, the refractive index of the p-type cladding can be made smaller than that of the n-type cladding. Consequently, the intensity distribution of the laser can be biased toward the n-type cladding side. That is, the laser propagating in the p-type cladding can be reduced, so the free carrier loss caused by impurities in the p-type cladding can be decreased. Thereby, low loss of the waveguide can be achieved. <​​​​​​​​​​​​​​

[0305] Next, an n-type cladding layer is formed on top of the substrate (S20). In this embodiment, an n-type (Al) cladding layer is formed on the upper surface of the substrate as an n-type cladding layer. yn2 Ga 1-yn2 ) 0.5 In 0.5 P layer.

[0306] Next, an n-side guiding layer is formed above the n-type cladding (S30). In this embodiment, an n-type (Al) layer is formed on the upper surface of the n-type cladding as an n-side guiding layer. 0.04 Ga 0.96 ) 0.5 In 0.5 P layer.

[0307] Next, an active layer is formed above the n-side guiding layer (S40). In this embodiment, as the active layer, an n-side first barrier layer, an n-side second barrier layer, a well layer, a p-side barrier layer, and a p-side guiding layer are sequentially formed on the upper surface of the n-side guiding layer. Specifically, an undoped Al is formed as the n-side first barrier layer. 0.5 Ga 0.5 An As layer is formed as the second barrier layer on the n-side, resulting in undoped Al. 0.55 Ga 0.45 An As layer is formed as a well layer to create an undoped In layer. 0.08 Ga 0.92 An As layer is formed as a p-side barrier layer to create undoped Al. 0.59 Ga 0.16 In 0.25 The As layer, acting as a p-side guiding layer, forms a p-type (Al) layer. ygp2 Ga 1-gp2 ) 0.5 In 0.5 P layer.

[0308] Next, a p-type cladding layer is formed above the active layer (S50). In this embodiment, a p-type (Al) cladding layer is formed on the upper surface of the active layer. yp2 Ga 1-yp2 ) 0.5 In 0.5 P layer.

[0309] Next, a current-restricting layer is formed above the p-type cladding (S60). In this embodiment, an n-type GaAs layer is formed on the upper surface of the p-type cladding as a current-restricting layer, and an elongated opening is formed along the laser resonance direction by photolithography and etching.

[0310] Next, a contact layer is formed above the current-restricting layer (S70). In this embodiment, a p-type GaAs layer is formed as a contact layer on the upper surface and opening of the current-restricting layer.

[0311] The aforementioned semiconductor layers are formed, for example, by metal-organic vapor deposition (MOCVD).

[0312] Next, an end-face window structure is formed on the active layer (S80). Specifically, vacancies or impurities are diffused from the upper surface of the contact layer toward the light-emission end face of the active layer. By diffusing vacancies or impurities in this way, the quantum well structure at the light-emission end face of the active layer can be disordered. Consequently, the band gap energy of the active layer can be increased. That is, a window structure can be formed. In this embodiment, an n-type (Al) cladding is formed. yn2 Ga 1-yn2 ) 0.5 In 0.5 The P-layer, acting as a p-side guiding layer, forms the p-type (Al) ygp2 Ga 1-gp2 ) 0.5 In 0.5 The P-layer, acting as a p-type cladding, forms the p-type (Al) layer. yp2 Ga 1-yp2 ) 0.5 In 0.5 The P-layer facilitates the diffusion of vacancies or impurities. This reduces the time required to form the end-face window structure. Furthermore, since the concentration of impurities used for diffusion can be reduced, light absorption due to impurities is minimized. Therefore, the decrease in luminous efficiency of the semiconductor light-emitting element can be suppressed. In addition, the end-face window structure can be formed not only at the light-emitting end face but also at both ends of the semiconductor light-emitting element where a resonator is formed.

[0313] 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 main surface below the substrate. In this embodiment, as the p-side electrode, a Ti film, a Pt film, and an Au film are sequentially formed from the contact layer side, and as the n-side electrode, 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 sequentially formed from the substrate 10 side.

[0314] As described above, the semiconductor light-emitting element of this embodiment can be manufactured.

[0315] (variant examples, etc.)

[0316] The semiconductor light-emitting element and its manufacturing method of the present invention have been described above based on various embodiments, but the present invention is not limited to the above embodiments.

[0317] For example, in the above embodiments, examples of semiconductor light-emitting elements being semiconductor laser elements are shown, but semiconductor light-emitting elements are not limited to semiconductor laser elements. For example, a semiconductor light-emitting element may also be a super luminescent diode.

[0318] Furthermore, while AlGaInAs-based materials are used in the above embodiments for the semiconductor light-emitting element, other semiconductor materials may also be used. For example, nitride-based semiconductor materials may also be used. Specifically, AlGaInN-based materials may also be used. The conduction band potential and valence band potential of AlGaInAs-based materials and AlGaInN-based materials will be explained below.

[0319] The physical properties affecting the conduction band potential energy and valence band potential energy are electron affinity, band gap energy, and lattice strain. Lattice strain is determined by the lattice constant of the semiconductor layer and the lattice constant of the substrate on which the semiconductor layer is stacked. In AlGaInAs and AlGaInN materials, within the binary compounds (AlAs, GaAs, and InAs, and AlN, GaN, and InN) that are their constituent elements, the order of electron affinity, band gap energy, and lattice constant is as follows: Regarding electron affinity, it decreases in the order of InAs, GaAs, and AlAs, and in the order of InN, GaN, and AlN. The band gap energy decreases in the order of AlAs, GaAs, and InAs, and in the order of AlN, GaN, and InN. Regarding the lattice constants of the constituent elements of AlGaInAs materials, InAs is larger than GaAs and AlAs, while GaAs and AlAs are of similar magnitude. Furthermore, regarding the lattice constants of the constituent elements of AlGaInN materials, InN is larger than GaN and AlN, while GaN and AlN are of the same degree.

[0320] Based on the above relationships, it can be seen that even if the group V atoms of the quaternary semiconductor materials are different, the magnitude relationship of the above properties is similar.

[0321] Among AlAs, GaAs, and InAs, which are the constituent elements of AlGaInAs-type materials, InAs has the largest lattice constant and the smallest band gap energy. When using quaternary semiconductor materials containing AlGaInAs for both the well layer and the barrier layer to obtain the desired band gap energy, compared to using an InGaAs layer for the well layer to obtain the desired band gap, the In content of the AlGaInAs well layer is higher, resulting in a larger compressive strain in the well layer.

[0322] Among AlGaInN-type materials, InN has the largest lattice constant and the smallest bandgap energy among AlN, GaN, and InN. When using AlGaInN-type quaternary semiconductor materials for both the well and barrier layers to achieve the desired bandgap energy, compared to using InGaN for the well layer or AlGaN for the barrier layer, the increased In content in the AlGaInN-based well layer leads to greater compressive strain in the well layer.

[0323] Furthermore, the relationship that the more In a material contains, the greater the electron affinity, and the more Al a material contains, the smaller the electron affinity, applies to both AlGaInAs and AlGaInN materials.

[0324] Therefore, if an AlGaInAs-type material is used for the barrier layer, increasing the In content and increasing the band gap energy results in a larger change in conduction band potential energy (ΔEbc) than in valence band potential energy (ΔEbv), and this is also true for AlGaInN-type materials. Therefore, AlGaInN-type quaternary semiconductor materials can also be used as materials for forming the semiconductor light-emitting elements of the above embodiments. For example, the semiconductor light-emitting element 1a of Variation 1 of Embodiment 1 can also include a substrate made of GaN substrate and a 1.5 μm thick AlGaInN substrate. 0.25 Ga 0.75 N (Si concentration: 1×10) 18 cm -3 An n-type cladding composed of Al, with a film thickness of 30 nm. 0.2 Ga 0.8 The first barrier layer on the n-side, composed of N, with a thickness of 2.8 nm, is made of Al. 0.01 Ga 0.98 In 0.01 The well layer is composed of N, and the film thickness is 7nm. 0.40 Ga 0.515 In 0.085 The p-side barrier layer is composed of N, and the film thickness is 30 nm. It is made of Al. 0.2 Ga 0.8 The p-side guiding layer is composed of N and the film thickness is 0.6 μm made of Al. 0.3 Ga 0.7 N (Mg concentration: 1×10) 19 cm -3 The p-type cladding is composed of π / 3. This allows for the production of ultraviolet lasers with an oscillation wavelength of 360 nm, and enables the development of nitride-based semiconductor light-emitting devices that suppress electron leakage from the well layer while suppressing the operating voltage.

[0325] Furthermore, if a p-type impurity is doped in at least one of the p-side intermediate layer 14e, the p-side barrier layer 14f, and the p-side guiding layer 14g, the conduction band potential energy of that layer increases. Therefore, the effect of suppressing electron overflow during high-temperature, high-output operation can be improved. Furthermore, in this case, since the resistance of the layer doped with the p-type impurity is reduced, the series resistance component in the semiconductor light-emitting element can be reduced. Consequently, the generation of Joule heating during operation can also be suppressed, thus further improving the thermally saturated light output of the semiconductor light-emitting element during high-temperature operation. As the p-type impurity, C (carbon atoms) or Mg, which do not easily diffuse from the doped site, can be used.

[0326] Here, the doping concentration, in the case of AlGaInAs-like materials containing AlGaAs, can be 1×10⁻⁶ to improve electrical conductivity and conduction band potential energy. 17 cm -3 The above can also be 2×10 17 cm -3 That's all. Furthermore, if the doping concentration of impurities in the p-side intermediate layer 14e, p-side barrier layer 14f, and p-side guiding layer 14g near the well layer 14d is excessively increased, the free carrier loss becomes higher, leading to a decrease in the luminous efficiency of the semiconductor light-emitting element. Therefore, the doping concentration in these layers can be 1×10⁻⁶. 18 cm -3 The following can also be 6×10 17 cm -3 the following.

[0327] Furthermore, in the case of AlGaInN-type materials containing AlGaN, when Mg is used as a dopant, the doping concentration can be 1×10⁻⁶ to improve electrical conductivity and conduction band potential energy. 18 cm -3 The above can also be 2×10 18 cm -3 That's all. Furthermore, if the doping concentration of impurities in the p-side intermediate layer 14e, p-side barrier layer 14f, and p-side guiding layer 14g near the well layer 14d is excessively increased, the free carrier loss becomes higher, leading to a decrease in the luminous efficiency of the semiconductor light-emitting element. Therefore, the doping concentration in these layers can be 1×10⁻⁶. 19 cm -3 The following can also be 6×10 18 cm -3 the following.

[0328] Furthermore, when at least one of the p-side intermediate layer 14e, the p-side barrier layer 14f, and the p-side guiding layer 14g is doped, the p-type impurity doping concentration can result in a relatively low concentration closer to the well layer 14d. This reduces the impurity concentration in the impurity-doped region closest to the well layer 14d, which serves as the light-emitting layer, thus decreasing free carrier losses. Consequently, waveguide losses of the laser propagating in the waveguide can be reduced.

[0329] Furthermore, the present invention also includes various modifications conceived by those skilled in the art to the above embodiments, or forms achieved by arbitrarily combining the constituent elements and functions of the above embodiments without departing from the spirit of the present invention.

[0330] For example, the various modifications of Embodiment 1 can be combined with each other or with other embodiments. For example, the end-face window structure of Modification 7 of Embodiment 1 can also be applied to other modifications and embodiments of Embodiment 1. Furthermore, regarding the use of nitride-based semiconductor materials, among AlN, GaN, and InN, InN has the largest lattice constant and the smallest bandgap energy. In this case, when the desired bandgap energy is obtained by using a layer containing a quaternary semiconductor material composed of AlGaInN for the well layer and each barrier layer, compared to obtaining the desired bandgap energy by using InGaN or AlGaN for the well layer, the In content of the well layer composed of AlGaInN is increased, thus the compressive strain of the well layer is larger. Therefore, similar to the case where the well layer and each barrier layer use a layer containing AlGaInAs-type materials, a window structure can be easily formed.

[0331] Furthermore, the manufacturing method of the semiconductor light-emitting element in Embodiment 4 can also be applied to the manufacturing of semiconductor light-emitting elements in other embodiments and variations. For example, in the manufacturing of semiconductor light-emitting elements in Embodiment 1 and its variations, a manufacturing method that omits the n-side guiding layer formation step and modifies the structure of each semiconductor layer can be applied. Furthermore, in the manufacturing of the semiconductor light-emitting element 101 in Embodiment 2, a manufacturing method that adds a first strain control layer 15 and a second strain control layer 16 to the semiconductor light-emitting element manufacturing method of Embodiment 4 and modifies the structure of each semiconductor layer can be applied. Furthermore, in the manufacturing of the semiconductor light-emitting element 201 in Embodiment 3, a manufacturing method that omits the current-limiting layer formation step in the p-type cladding formation step of the semiconductor light-emitting element manufacturing method of Embodiment 4, adds a step to form a raised portion of the p-type cladding and contact layer, and a step to form a current-blocking layer 20, and modifies the structure of each semiconductor layer can be applied.

[0332] Industrial availability

[0333] The semiconductor light-emitting element of the present invention can be used as a light source for laser processing, for example, as a high-output and high-efficiency light source.

[0334] Explanation of reference numerals in the attached figures

[0335] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 101, 201 Semiconductor light-emitting elements

[0336] 10 substrate

[0337] 11 Buffer Layer

[0338] 12 n-type cladding

[0339] 13 n-side guidance layer

[0340] 14. Active layer

[0341] 14a n-side first barrier layer

[0342] 14b n-side second barrier layer

[0343] 14c n-side third barrier layer

[0344] 14d well layer

[0345] 14e p-side intermediate layer

[0346] 14f p-side barrier layer

[0347] 14g p-side guide layer

[0348] 14h, 14ha First intermediate barrier layer

[0349] 14i First intermediate n-side barrier layer

[0350] 14j First intermediate p-side barrier layer

[0351] 15 First Strain Control Layer

[0352] 16 Second Strain Control Layer

[0353] 17 p-type cladding

[0354] 18, 218 contact layers

[0355] 19 Current Narrow Layer

[0356] 19a Opening

[0357] 20 Current blocking layer

[0358] 31 n-side electrode

[0359] 32 p-side electrode

[0360] 40 Light emission end face

[0361] 202 Subassemblies

[0362] 218r ridge

[0363] 218t tank

Claims

1. A semiconductor light-emitting device, characterized in that: It 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 has: A well layer; An n-side first barrier layer disposed on the n-type cladding layer side of the well layer, composed of a quaternary semiconductor material containing Al, Ga, In, and group V atoms; and A p-side barrier layer disposed on the p-type cladding layer side of the well layer, composed of a quaternary semiconductor material containing Al, Ga, In, and the group V atoms; The p-side barrier layer contains In; The In component ratio of the n-side first barrier layer is lower than the In component ratio of the p-side barrier layer; The bandgap energy of the n-side first barrier layer is less than the bandgap energy of the p-side barrier layer; The Al component ratio of the n-side first barrier layer is lower than the Al component ratio of the p-side barrier layer.

2. The semiconductor light-emitting device according to claim 1, characterized in that: The components of the first barrier layer on the nth side are composed of Al ybn1 Ga 1-xbn1-ybn1 In xbn1 As indicates; The components of the above p-side barrier layer are Al ybp1 Ga 1-xbp1-ybp1 In xbp1 As indicates; The relationships of 0≦ybn1≦1, 0≦xbn1<1, 0<ybp1<1, 0<xbp1<1, and xbn1<xbp1 hold.

3. A semiconductor light-emitting device, characterized in that: It 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 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; The In component ratio of the n-side first barrier layer is lower than the In component ratio of the p-side barrier layer; The bandgap energy of the n-side first barrier layer is less than the bandgap energy of the p-side barrier layer; The components of the first barrier layer on the nth side are composed of Al ybn1 Ga 1-xbn1-ybn1 In xbn1 As indicates; The components of the above p-side barrier layer are Al ybp1 Ga 1-xbp1-ybp1 In xbp1 As indicates; The relationships of 0≦ybn1≦1, 0≦xbn1<1, 0<ybp1<1, 0<xbp1<1, and xbn1<xbp1 hold; Furthermore, the relationship of ybn1<ybp1 holds.

4. The semiconductor light-emitting device according to claim 2 or 3, characterized in that: Furthermore, 0.2≦ybn1≦0.4 ybp1≦xbp1 + 0.975ybn1 + 0.069, ybp1≧0.4xbp1 + 0.975ybn1 + 0.029, and The relationship of xbp1≦0.15 holds.

5. The semiconductor light-emitting device according to claim 2 or 3, characterized in that: It further includes a p-side intermediate layer disposed between the well layer and the p-side barrier layer; The components of the above p-side intermediate layer are composed of Al ykp1 Ga 1-ykp1 As indicates; ybp1≦xbp1 + 0.975ykp1 + 0.069, ybp1≧0.4xbp1 + 0.975ykp1 + 0.029, and The relationship of 0.2≦ykp1≦0.4 holds.

6. The semiconductor light-emitting device according to claim 2 or 3, characterized in that: It further includes an n-side second barrier layer disposed between the n-side first barrier layer and the well layer; The components of the second barrier layer on the nth side are Al ybn2 Ga 1-xbn2-ybn2 In xbn2 As indicates; ybn2≧xbn2 + ybn1, ybn2≦0.4xbn2 + 0.975ybn1 + 0.061, xbn2 ≤ 0.15, and the relationship 0.2 ≤ ybn1 ≤ 0.35 holds.

7. The semiconductor light-emitting device according to claim 6, wherein it further includes an n-side third barrier layer disposed between the well layer and the n-side second barrier layer; The components of the aforementioned n-side third barrier layer are composed of Al ybn3 Ga 1-ybn3 As indicates; ybn2 ≥ xbn2 + ybn3, ybn2 ≤ 0.4xbn2 + 0.975ybn3 + 0.061, and the relationship 0.2 ≤ ybn3 ≤ 0.35 holds.

8. The semiconductor light-emitting device according to claim 2 or 3, wherein it further includes a p-side guiding layer disposed between the p-side barrier layer and the p-type cladding layer and having a refractive index greater than that of the p-type cladding layer.

9. The semiconductor light-emitting device according to claim 8, wherein The components of the aforementioned p-side guiding layer are composed of Al ygp1 Ga 1-ygp1 As indicates; ybp1 ≤ xbp1 + 0.975ygp1 + 0.069, ybp1 ≥ 0.4xbp1 + 0.975ygp1 + 0.029, and the relationship 0.2 ≤ ygp1 ≤ 0.4 holds.

10. The semiconductor light-emitting device according to claim 8, wherein The aforementioned p-side guiding layer is composed of (Al) ygp2 Ga 1-ygp2 ) 0.5 In 0.5 P represents...

11. The semiconductor light-emitting device according to any one of claims 1 to 3, wherein The components of the above n-type cladding are composed of Al yn1 Ga 1-yn1 As indicates; The components of the above p-type cladding are composed of Al yp1 Ga 1-yp1 As indicates; the relationship 0 < yn1 < yp1 < 1 holds.

12. The semiconductor light-emitting device according to any one of claims 1 to 3, wherein The above n-type cladding is composed of (Al) yn2 Ga 1-yn2 ) 0.5 In 0.5 P represents; The above-mentioned p-type cladding consists of (Al) yp2 Ga 1-yp2 ) 0.5 In 0.5 P represents; the relationship 0 < yn2 < yp2 < 1 holds.

13. The semiconductor light-emitting device according to any one of claims 1 to 3, wherein The components of the above-mentioned trap layer are composed of Al yw Ga 1-xw-yw In xw As indicates; the relationships 0 ≤ yw < 1 and 0 < xw < 1 hold.

14. The semiconductor light-emitting device according to claim 13, wherein furthermore, the relationship 0 < yw < 1 holds.

15. The semiconductor light-emitting device according to any one of claims 1 to 3, wherein the substrate is a GaAs substrate.

16. The semiconductor light-emitting device according to any one of claims 1 to 3, wherein the bandgap energy of the n-type cladding layer is smaller than the bandgap energy of the p-type cladding layer.

17. The semiconductor light-emitting device according to any one of claims 1 to 3, wherein an end-face window structure is formed on the light-emitting end face portion of the active layer.

18. The semiconductor light-emitting device according to claim 17, wherein the bandgap energy of the portion of the active layer where the end-face window structure is formed is larger than the bandgap energy of the portion of the active layer where the end-face window structure is not formed.

19. A semiconductor light-emitting device, comprising: 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 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; the In component ratio of the n-side first barrier layer is lower than the In component ratio of the p-side barrier layer; the bandgap energy of the n-side first barrier layer is smaller than the bandgap energy of the p-side barrier layer; ​ The aforementioned n-type cladding, active layer, and p-type cladding are composed of nitride-based semiconductor materials.

20. A method for manufacturing a semiconductor light-emitting element, characterized in that, The process includes the following steps: The process of preparing the substrate; The process of forming an n-type cladding layer on top of the aforementioned substrate; The process of forming an active layer above the aforementioned n-type cladding; The process of forming a p-type cladding layer above the aforementioned active layer; and The process of forming an end-face window structure in the above-mentioned active layer; The above-mentioned active layer has: trap layer; The first barrier layer on the n-side, disposed on the n-type cladding side of the well layer, is composed of a quaternary semiconductor material containing Al, Ga, In, and group V atoms; and The p-side barrier layer, disposed on the p-type cladding side of the well layer, is composed of a quaternary semiconductor material containing Al, Ga, In, and the aforementioned group V atoms. The aforementioned p-side barrier layer contains In; The In component ratio of the first barrier layer on the n-side is lower than the In component ratio of the barrier layer on the p-side. The bandgap energy of the first barrier layer on the n-side is less than the bandgap energy of the barrier layer on the p-side. In the process of forming the above-mentioned end-face window structure, vacancies or impurities are diffused in the above-mentioned active layer. The Al composition ratio of the first barrier layer on the n-side is lower than that of the barrier layer on the p-side.

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