Semiconductor light-emitting element

Abstract

This semiconductor light-emitting element comprises: a substrate made of InP; an active layer located on the substrate; a plurality of P-side separate confinement heterostructure layers located adjacent to the active layer; an N-side separate confinement heterostructure layer located adjacent to the active layer on a side opposite to the P-side separate confinement heterostructure portion; a P-type semiconductor layer located adjacent to the P-side separate confinement heterostructure portion on a side opposite to the active layer; and an N-type semiconductor layer located adjacent to the N-side separate confinement heterostructure layer on a side opposite to the active layer. The plurality of P-side separate confinement heterostructure layers include a plurality of AlInAsP layers in which the ratio of the difference between the film-thickness-weighted average of lattice constants thereof and the lattice constant of InP to the lattice constant of InP is within a range of ±0.3%. In the plurality of P-side separate confinement heterostructure layers, the valence band maximum energy increases stepwise or continuously toward the active layer.

Description

Semiconductor light-emitting device

[0001] The present invention relates to a semiconductor light-emitting device.

[0002] A semiconductor light-emitting device is used, for example, as a light source that outputs signal light in optical communication. In optical communication, high-temperature operation may be required for the semiconductor light-emitting device. Auger recombination between electrons and holes in the active layer of the semiconductor light-emitting device is a limiting factor for the high-temperature operation of the semiconductor light-emitting device. In contrast, in Non-Patent Document 1, it is disclosed that by using a quantum well formed by a type-II heterojunction structure and appropriately adjusting the band offsets of the conduction band and the valence band, a reduction in Auger recombination is theoretically predicted.

[0003] On the other hand, as a structure for improving the optical confinement effect in a semiconductor light-emitting device, a SCH (Separate Confinement Heterostructure) is known. Hereinafter, in this specification, the separate confinement heterostructure layer may be referred to as a SCH layer. For example, in Patent Document 1, a semiconductor laser is disclosed in which a GaInAsP layer is used as the N-side SCH layer and an AlGaInAs layer is used as the P-side SCH layer for an active layer made of GaInAsP.

[0004] Japanese Patent Application Laid-Open No. 5-110193

[0005] G.G. Zegrya and A.D. Andreev, "Mechanism of suppression of Auger recombination processes in type-II heterostructures", Applied Physics Letters, vol.67, Issue 18, pp2681-2683, 1995

[0006] However, when a GaInAsP layer is used as the P-side SCH layer in a semiconductor light-emitting device, the lower energy of the conductor of GaInAsP is relatively low. As a result, electrons supplied toward the active layer may leak to the P-side SCH layer, potentially degrading the high-temperature operating characteristics of the semiconductor light-emitting device. Furthermore, when an AlGaInAs layer is used as the P-side SCH layer, the upper energy of the valence band of the P-side SCH layer may be higher than that of the active layer. This can create a barrier for holes supplied toward the active layer due to band offset in the valence band, potentially reducing hole transport efficiency. In this case, the operating voltage of the semiconductor light-emitting device increases, leading to increased heat generation and potentially degrading the high-temperature operating characteristics of the semiconductor light-emitting device.

[0007] The present invention has been made in view of the above, and aims to provide a semiconductor light-emitting element with good high-temperature operating characteristics.

[0008] One aspect of the present invention is a semiconductor light-emitting element comprising: a substrate made of InP; an active layer located on the substrate; a plurality of P-side isolated-confinement heterostructure layers located adjacent to the active layer; an N-side isolated-confinement heterostructure layer located adjacent to the active layer on the opposite side of the plurality of P-side isolated-confinement heterostructures; a P-type semiconductor layer located adjacent to the plurality of P-side isolated-confinement heterostructures on the opposite side of the active layer; and an N-type semiconductor layer located adjacent to the N-side isolated-confinement heterostructure layer on the opposite side of the active layer, wherein the plurality of P-side isolated-confinement heterostructure layers include a plurality of AlInAsP layers in which the ratio of the difference between the film thickness weighted average of their lattice constants and the lattice constant of InP to the lattice constant of InP is within ±0.3%; and in the plurality of P-side isolated-confinement heterostructure layers, the valence band upper edge energy increases stepwise or continuously as it approaches the active layer.

[0009] The valence band upper energy of the P-side isolated confinement heterostructure layer may be the energy between the valence band upper energy of the P-type semiconductor layer and the valence band upper energy of the layer adjacent to the P-side isolated confinement heterostructure layer in the active layer.

[0010] The AlInAsP layer may have a conduction band lower energy greater than that of the P-type semiconductor layer.

[0011] The plurality of AlInAsP layers may include AlInAsP layers having a band gap larger than the band gap of the P-type semiconductor layer.

[0012] The plurality of AlInAsP layers may include AlInAsP layers having the same lattice constant as InP, and arranged such that the Al composition ratio and As composition ratio increase stepwise or continuously as they approach the active layer.

[0013] The Al composition ratio may be between 0 and 0.48.

[0014] The Al composition ratio may be 0.2 or more and 0.48 or less.

[0015] The plurality of AlInAsP layers may include AlInAsP layers having a lattice constant smaller than that of InP.

[0016] The ratio of the difference between the lattice constant of the AlInAsP layer, which has a lattice constant smaller than that of InP, and the lattice constant of InP, to the lattice constant of InP may be -0.3% or less.

[0017] The plurality of AlInAsP layers may include AlInAsP layers having a lattice constant larger than that of InP.

[0018] The plurality of AlInAsP layers may have the same Al composition ratio, and may be arranged such that the As composition ratio increases stepwise or continuously as it approaches the active layer.

[0019] The plurality of AlInAsP layers may have the same As composition ratio, and may be arranged such that the Al composition ratio decreases gradually or continuously as it approaches the active layer.

[0020] The plurality of P-side separated and confined heterostructure layers may include a GaInAsP layer.

[0021] The P-side separated confinement heterostructure layer does not necessarily have to be intentionally doped with impurities.

[0022] The P-side separated confinement heterostructure layer is 8.0 × 10 １７ cm －３ P-type impurities may be doped at the following concentrations.

[0023] The active layer may include a type II heterojunction structure formed by a hole quantum well layer made of AlGaInAs and an electron quantum well layer made of GaInAsP.

[0024] The valence band upper energy of the P-side separated confinement heterostructure layer may be the energy between the valence band upper energy of the P-type semiconductor layer and the valence band upper energy of the electron quantum well layer.

[0025] The active layer may include a type I heterojunction structure formed by a quantum well layer made of GaInAsP and a barrier layer made of GaInAsP having a different composition from that of the quantum well layer.

[0026] The valence band upper energy of the P-side separated confinement heterostructure layer may be the energy between the valence band upper energy of the P-type semiconductor layer and the valence band upper energy of the barrier layer.

[0027] According to the present invention, a semiconductor light-emitting element with good high-temperature operating characteristics can be realized.

[0028] Figure 1 is a schematic cross-sectional view of a semiconductor light-emitting element according to Embodiment 1. Figure 2 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element according to Embodiment 1 that includes the active layer. Figure 3 is a diagram showing the case when a voltage is applied to the energy band in Figure 2. Figure 4 is a diagram showing the relationship between the lower edge energy of the conduction band and the upper edge energy of the valence band of a mixed crystal lattice-matched with an InP substrate. Figure 5 is a diagram showing an example of the relationship between the strain of the crystal lattice and the critical film thickness in an AlInAsP layer. Figure 6 is a diagram showing an example of the relationship between the Al composition ratio and the refractive index, and the relationship between the Al composition ratio and the upper edge energy of the valence band in an AlInAsP layer. Figure 7 is a diagram showing the relationship between the lower edge energy of the conduction band and the upper edge energy of the valence band in the case of AlInAsP with different strains. Figure 8 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element according to Embodiment 2 that includes the active layer. Figure 9 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element according to Embodiment 3 that includes the active layer. Figure 10 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element according to Embodiment 4 that includes the active layer. Figure 11 shows an example of the structure and energy band of the portion of a semiconductor light-emitting element including the active layer according to Embodiment 5. Figure 12 shows an example of the structure and energy band of the portion of a semiconductor light-emitting element including the active layer according to Embodiment 6. Figure 13 shows the case when a voltage is applied when a P-type impurity is doped into the P-side SCH layer. Figure 14 shows the relationship between the lower end energy of the conduction band and the upper end energy of the valence band of a mixed crystal lattice-matched with an InP substrate. Figure 15 shows an example of the structure and energy band of the portion of a semiconductor light-emitting element including the active layer according to Embodiment 7.

[0029] Embodiments will be described below with reference to the drawings. However, this embodiment does not limit the present invention. Furthermore, in the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and redundant explanations are omitted as appropriate. It should also be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from reality. Even between drawings, there may be parts where the dimensional relationships and ratios differ.

[0030] (Embodiment 1) [Overall Configuration of Semiconductor Light-Emitting Device] Figure 1 is a schematic cross-sectional view of a semiconductor light-emitting device according to Embodiment 1. The semiconductor light-emitting device 100 is configured as a semiconductor laser element. The semiconductor light-emitting device 100 comprises an N-type semiconductor portion 2 with an N-side electrode 1 formed on its back surface, an N-side SCH layer (N-side isolated confinement heterostructure layer) 3, an active layer 4, a P-side SCH portion 5 including a plurality of P-side SCH layers (P-side isolated confinement heterostructure layers), a P-type semiconductor portion 6, a guide layer 7, a current blocking layer 8, a contact layer 9, and a P-side electrode 10. The semiconductor light-emitting device 100 outputs laser light from the active layer 4 in a direction perpendicular to the plane of the paper.

[0031] The N-type semiconductor portion 2 comprises a substrate 2a and an N-type cladding layer 2b located on the substrate 2a with the stacking direction facing upwards.

[0032] The substrate 2a is made of N-type InP (hereinafter referred to as N-InP as appropriate). The N-type cladding layer 2b is a layer made of n-InP that is laminated on the substrate 2a by epitaxial growth or the like.

[0033] In this specification, the N-type semiconductor layer contains, for example, silicon (Si), sulfur (S), and selenium (Se) as N-type impurities, but the N-type impurities are not particularly limited.

[0034] The N-side SCH layer 3, the active layer 4, and the P-side SCH portion 5 are located on the substrate 2a. Specifically, the P-side SCH portion 5 is located adjacent to the active layer 4. The N-side SCH layer 3 is located adjacent to the active layer 4 on the opposite side from the P-side SCH portion 5. The structure and characteristics of the N-side SCH layer 3, the active layer 4, and the P-side SCH portion 5 will be described in detail later.

[0035] The P-type semiconductor portion 6 has a stacked structure of semiconductor layers 6a, 6b, and 6c made of P-type InP (hereinafter referred to as P-InP as appropriate).

[0036] In this specification, the p-type semiconductor layer contains, for example, zinc (Zn) as a p-type impurity, but the p-type impurity is not particularly limited.

[0037] The guide layer 7 is located between the semiconductor layers 6a and 6b. The guide layer 7 has a higher refractive index than InP and is made of, for example, p-type GaInAsP. The guide layer 7 may be lattice-matched with InP; that is, the lattice constant of the GaInAsP constituting the guide layer 7 may be equal to the lattice constant of InP.

[0038] The guide layer 7 and a portion of the P-type semiconductor portion 6 have a stripe mesa structure. The stripe mesa structure is made to a width (for example, 2 μm) suitable for guiding the light emitted by the active layer 4 in single mode by etching or the like. Both sides of the stripe mesa structure (left and right directions in the drawing) are embedded by a current blocking layer 8, which is constructed by stacking a current blocking layer 8a made of P-InP and a current blocking layer 8b made of N-InP. The semiconductor layer 6c is formed to cover the semiconductor layer 6b and the current blocking layer 8.

[0039] The contact layer 9 is made of, for example, P-type GaInAsP and makes ohmic contact with the P-side electrode 10. The P-side electrode 10 contains, for example, titanium, platinum, or gold.

[0040] The N-side electrode 1 is provided to make ohmic contact with the substrate 2a. The N-side electrode 1 may contain, for example, gold or nickel.

[0041] In the above, the semiconductor layer 6a is an example of a P-type semiconductor layer located adjacent to the P-side SCH portion 5 on the opposite side of the active layer 4. The N-type cladding layer 2b is an example of an N-type semiconductor layer located adjacent to the N-side SCH layer 3 on the opposite side of the active layer 4.

[0042] Furthermore, both end faces of the semiconductor light-emitting element 100, parallel to the drawing, are end faces formed by cleavage. A relatively high reflectivity HR (High Reflection) film is formed on one end face, and an anti-reflection AR (Anti-Reflection) film is formed on the other end face. The HR film and the AR film form a laser resonator. When current is injected from the P-side electrode 10, the semiconductor light-emitting element 100 outputs laser light mainly from the end face where the AR film is formed.

[0043] [Structure and Characteristics of N-Side SCH Layer, Active Layer, and P-Side SCH Section] FIG. 2 is a diagram showing an example of the structure and energy band of a portion including the active layer 4 of the semiconductor light-emitting device 100. Note that the energy on the vertical axis in the figure is the energy based on the vacuum level. Line L1 indicates the energy level at the upper end of the valence band, and line L2 indicates the energy level at the lower end of the conduction band.

[0044] The N-side SCH layer 3 is made of, for example, GaInAsP that is lattice-matched with InP. The composition of GaInAsP in this embodiment is Ga ０．０６ InAs ０．１３ P. The N-side SCH layer 3 may not be intentionally doped with impurities.

[0045] The active layer 4 has a structure in which an electron well layer 4a, a hole well layer 4b, and an electron well layer 4c are arranged in this order in the stacking direction. The electron well layers 4a and 4c are made of, for example, GaInAsP. The composition of the electron well layers 4a and 4c in this embodiment is Ga ０．３０ InAs ０．５６ P. The hole well layer 4b is made of AlGaInAs. The composition of the hole well layer 4b in this embodiment is Al ０．２５ Ga ０．０８ InAs. The electron well layer 4a, the hole well layer 4b, and the electron well layer 4c form a so-called W-type type-II heterojunction structure. As a result, in the active layer 4, electrons are confined in the electron well layer 4a or 4c, and holes are confined in the hole well layer 4b.

[0046] The P-side SCH section 5 includes P-side SCH layers 5a, 5b, 5c, and 5d that are a plurality of P-side SCH layers. The P-side SCH layers 5a, 5b, 5c, and 5d are all AlInAsP layers made of AlInAsP. The compositions of the P-side SCH layers 5a, 5b, 5c, and 5d in this embodiment are, respectively, Al ０．３８ InAs ０．８ P, Al ０．３３ InAs ０．７ P, Al ０．２８ InAs ０．６ P, Al ０．２５ InAs ０．５３It is P. The P-side SCH layers 5a, 5b, 5c, and 5d have the same lattice constant as InP. Therefore, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5a, 5b, 5c, and 5d and the lattice constant of InP, relative to the lattice constant of InP, is within ±0.3%. Furthermore, the P-side SCH layers 5a, 5b, 5c, and 5d are not intentionally doped with impurities and are, for example, i-type semiconductors.

[0047] Furthermore, the P-side SCH layer 5a, which is an AlInAsP layer, has a band gap larger than the band gap of the P-type semiconductor layer 6a.

[0048] Table 1 shows the composition and thickness of each layer shown in Figure 2. As can be seen from Table 1, the P-side SCH layers 5a, 5b, 5c, and 5d are arranged such that the Al composition ratio and As composition ratio gradually increase as they approach the active layer 4.

[0049] Here, as shown in Figure 2, in the P-side SCH layers 5a, 5b, 5c, and 5d, the valence band upper energy indicated by line L1 increases stepwise as you approach the active layer 4.

[0050] In the semiconductor light-emitting element 100 configured as described above, the P-side SCH layers 5a, 5b, 5c, and 5d are made of AlInAsP, resulting in a large band offset between the P-side SCH portion 5 and the electron well layers 4a and 4c in the active layer 4 in the conduction band. This suppresses leakage of electrons supplied from the N-type cladding layer 2b towards the active layer 4 to the P-side SCH layers 5a, 5b, 5c, and 5d. Furthermore, in the P-side SCH layers 5a, 5b, 5c, and 5d, the upper valence band energy increases stepwise as it approaches the active layer 4, thus suppressing the formation of a high barrier against holes supplied from the P-type semiconductor layer 6a towards the active layer 4. For these reasons, the semiconductor light-emitting element 100 exhibits good high-temperature operation characteristics.

[0051] Furthermore, the P-side SCH layers 5a, 5b, 5c, and 5d can be made relatively thick while maintaining crystal quality because the ratio of the difference between the film thickness-weighted average of their lattice constants and the lattice constant of InP to the lattice constant of InP is within ±0.3%. As a result, the P-side SCH layers 5a, 5b, 5c, and 5d can be made thick enough to fully exhibit their light-trapping function.

[0052] Furthermore, as can be seen from Figure 2, the valence band upper energy of the P-side SCH layers 5a, 5b, 5c, and 5d is the energy between the valence band upper energy of the P-type semiconductor layer 6a and the valence band upper energy of the electron well layer 4c, which is adjacent to the P-side SCH layers 5a, 5b, 5c, and 5d in the active layer 4. This more effectively suppresses the formation of hole barriers and traps in the P-side SCH layers 5a, 5b, 5c, and 5d.

[0053] Furthermore, as can be seen from Figure 2, the P-side SCH layers 5a, 5b, 5c, and 5d, which are AlInAsP layers, have a lower conduction band energy greater than that of the P-type semiconductor layer 6a. As a result, the P-side SCH layers 5a, 5b, 5c, and 5d can reliably perform their function as an electron barrier.

[0054] Furthermore, the P-side SCH layer 5a is an AlInAsP layer having a band gap larger than the band gap of the P-type semiconductor layer 6a, and is therefore preferred as the P-side SCH layer.

[0055] Furthermore, since the P-side SCH layers 5a, 5b, 5c, and 5d are not intentionally doped with impurities, light absorption due to impurities can be suppressed to an extreme degree.

[0056] Furthermore, in the semiconductor light-emitting element 100, even when a stripe mesa structure is formed by etching or the like, the active layer 4 is not exposed, so there is no risk of the Al-containing layer coming into contact with air and oxidizing.

[0057] In Figure 2, as a comparative example, the P-side SCH portion 5 of the semiconductor light-emitting element 100 is made of Ga with a layer thickness of 10 nm, starting from the side closer to the active layer. ０．１３ In As ０．２８ P, Ga with a layer thickness of 10 nm ０．０９ In As ０．２１ P layer, Ga layer thickness 15 nm０．０６ In As ０．１３ P layer, Ga layer thickness 15 nm ０．０２ In As ０．０５ This shows the case where the P layer is replaced. The dashed line L3 indicates the energy level at the top of the valence band, and the dashed line L4 indicates the energy level at the bottom of the conduction band.

[0058] As shown in Figure 2, when the P-side SCH portion is made of GaInAsP, the formation of a high barrier to holes is suppressed as shown by line L3, but the band offset with the electron well layers 4a and 4c in the conduction band is small as shown by line L4.

[0059] Furthermore, Figure 3 shows the case when a voltage is applied to the energy band of Figure 2. Such a voltage is applied to supply electrons and holes to the active layer 4, and in Figure 3, a voltage of 0.95V is applied between the N-side electrode 1 and the P-side electrode 10. In Figure 3, lines L5 and L6 correspond to lines L1 and L2 in Figure 2, and lines L7 and L8 correspond to lines L3 and L4 in Figure 2. As can be seen from Figure 3, in the comparative form where the P-side SCH portion is GaInAsP, the band offset in the conduction band becomes even smaller when a voltage is applied, but in the semiconductor light-emitting element 100 where the P-side SCH portion 5 includes an AlInAsP layer, the magnitude of the band offset is sufficiently secured as indicated by arrow Ar1. However, in neither the embodiment nor the comparative form, a large barrier or trap is formed in region A1.

[0060] The following describes the P-side SCH layers 5a, 5b, 5c, and 5d in more detail. Figure 4 shows the relationship between the conduction band lower edge energy and the valence band upper edge energy of a mixed crystal lattice-matched with the InP substrate. The solid lines in the figure show the locus of coordinate points represented by the combination of conduction band lower edge energy and valence band upper edge energy when the composition ratio of GaInAsP, AlGaInAs, and AlInAsP lattice-matched with InP is changed. Note that "ε = 0%" means that the strain is zero. The energy difference between the valence band upper edge energy and the conduction band lower edge energy is the band gap, and the sloping dashed lines show the isoenergy lines of the band gap (from 0.4 eV to 1.9 eV). Also, in Figure 5, as an example, the electron well layer is Ga ０．３０ In As ０．５６ The coordinate points are shown for the case where P is the main component, and the white circles indicate that the hole well layer is Al. ０．２５ Ga ０．０８ The coordinate points are shown for the case where InAs is the basis.

[0061] Region A2 represents a desirable range for the P-side SCH layer. The desirable range for the P-side SCH layer is a range in which the conduction band lower edge energy is higher than the conduction band lower edge energy of the hole well layer, and the valence band upper edge energy is between the valence band upper edge energy of the cladding layer (P-type semiconductor layer) and the valence band upper edge energy of the electron well layer.

[0062] First, considering GaInAsP, which has the same lattice constant as InP, we find that GaInAsP is unsuitable as a P-side SCH layer because its conduction band lower energy is lower than that of the hole well layer. This is because electron leakage into the P-side SCH layer and a decrease in the overlap integral occur due to the leakage of electron wave functions into the P-side SCH layer.

[0063] Next, considering AlGaInAs, which has the same lattice constant as InP, we find that the AlGaInAs layer is unsuitable as the P-side SCH layer because its valence band upper energy is higher than that of the electron well layer. This is because a heterobarrier against holes is formed between the P-side SCH layer and the electron well layer, causing the driving voltage of the semiconductor light-emitting element to increase.

[0064] In contrast, when we consider AlInAsP, which has the same lattice constant as InP, we find that AlInAsP has a conduction band lower edge energy higher than that of the hole well layer, and its valence band upper edge energy is between the valence band upper edge energy of the cladding layer and the valence band upper edge energy of the electron well layer. Therefore, it can be seen that it is suitable as a P-side SCH layer.

[0065] Next, the preferred thickness of the AlInAsP layer will be described. Figure 5 shows an example of the relationship between the crystal lattice strain and the critical film thickness in the AlInAsP layer. In Figure 5, the As composition ratio is set to 70%, and the lattice constant is changed by changing the Al composition ratio, and the results are calculated using the Matthews-Blakeslee equation. In Figure 5, "a" on the horizontal axis is the lattice constant of InP, "Δa" is the difference between the lattice constant of AlInAsP and the lattice constant of InP, and "Δa / a" is the ratio of the difference between the lattice constant of InP and the lattice constant of AlInAsP to the lattice constant of InP, and corresponds to the strain.

[0066] As shown in Figure 5, in the AlInAsP layer, if the strain is 0.3% or less, the critical film thickness exceeds 100 nm, so an AlInAsP layer with good crystal quality can be formed. Therefore, in a structure in which multiple AlInAsP layers are stacked, such as the P-side SCH layers 5a, 5b, 5c, and 5d, it is preferable that the ratio of the difference between the film thickness-weighted average of the lattice constants of these layers and the lattice constant of InP to the lattice constant of InP is within the range of ±0.3%.

[0067] Next, Figure 6 shows an example of the relationship between the Al composition ratio and the refractive index in the AlInAsP layer, and the relationship between the Al composition ratio and the upper valence band energy. In Figure 6, the refractive index is the value at a wavelength of 1310 nm. Line L9 indicates the upper valence band energy of InP, and line L10 indicates the electron well layer is Ga ０．３０ In As ０．５６ This shows the valence band upper energy when the element is composed of P.

[0068] As can be seen from Figure 6, regardless of whether the Al composition ratio in the AlInAsP layer is between 0 and 0.48, the valence band upper energy of the AlInAsP layer is between the valence band upper energy of InP and the valence band upper energy of the electron well layer, making it preferable as a P-side SCH layer. Furthermore, if the Al composition ratio is between 0.2 and 0.48, the refractive index is relatively high, which is preferable from the viewpoint of light confinement.

[0069] (Embodiment 2) In Embodiment 1, all of the AlInAsP layers 5a, 5b, 5c, and 5d constituting the P-side SCH portion 5 have the same lattice constant as InP. However, some of the multiple AlInAsP layers constituting the P-side SCH portion 5 may include AlInAsP layers having a lattice constant smaller than that of InP.

[0070] Figure 7 shows the relationship between the lower conduction band energy and the upper valence band energy for AlInAsP with different strains. The solid lines in the figure show the cases where the strain (ε) for InP is -0.5%, -0.3%, 0%, 0.3%, and 0.5%. Note that the coordinate points of the electron well layer shown by black circles, the coordinate points of the hole quantum wells shown by white circles, and region A2 are the same as in Figure 4.

[0071] As can be seen from Figure 7, in AlInAsP layers having so-called stretching strain, where ε is smaller than the lattice constant of InP, such as -0.5% and -0.3%, the conduction band lower energy can be increased even if the valence band upper energy is the same, which is preferable in that it suppresses electron leakage due to band offset. In particular, if the difference between the lattice constant of the AlInAsP layer and the lattice constant of InP is between -0.3% and 0%, the conduction band lower energy is sufficiently high and the deterioration of crystal quality is suppressed, which is preferable.

[0072] Figure 8 shows an example of the structure and energy band of the portion of the semiconductor light-emitting element including the active layer according to Embodiment 2. The semiconductor light-emitting element 100A according to Embodiment 2 has a configuration in which the P-side SCH portion 5 of the semiconductor light-emitting element 100 according to Embodiment 1 is replaced with a P-side SCH portion 5A. Therefore, the P-side SCH portion 5A will be described mainly below, and the description of other components will be omitted as appropriate. In Figure 8, line L11 indicates the energy level at the upper end of the valence band, and line L12 indicates the energy level at the lower end of the conduction band.

[0073] The P-side SCH portion 5A of the semiconductor light-emitting element 100A includes a plurality of P-side SCH layers, namely P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad. All of the P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad are AlInAsP layers. In this embodiment, the compositions of the P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad are, respectively, Al ０．５２ In As, Al ０．４５ In As ０．８５ P, Al ０．２８ In As ０．６ P, Al ０．２５ In As ０．５３ It is P. Furthermore, the P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad are not intentionally doped with impurities.

[0074] Table 2 shows the composition and thickness of each layer shown in Figure 8, and the strain relative to InP. As can be seen from Table 2, the P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad are arranged such that the Al composition ratio and As composition ratio gradually increase as they approach the active layer 4.

[0075] As shown in Figure 8, in the P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad, the valence band upper energy, indicated by line L11, increases stepwise as you approach the active layer 4.

[0076] Furthermore, as shown in Table 2, the P-side SCH layers 5Ac and 5Ad have the same lattice constant as InP. In contrast, the P-side SCH layers 5Aa and 5Ab have a smaller lattice constant than InP and have a tensile strain of -0.3%. In this case, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad and the lattice constant of InP to the lattice constant of InP is within ±0.3%. Specifically, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Aa, 5Ab, 5Ac, and 5Ad and the lattice constant of InP to the lattice constant of InP is -0.12% (= (-0.3 × 10 - 0.3 × 10) / (10 + 10 + 15 + 15).

[0077] In the semiconductor light-emitting element 100A configured as described above, the same effects as the semiconductor light-emitting element 100 can be obtained, but since the band offset between the P-side SCH portion 5A and the electron well layers 4Aa and 4Ac is even larger, electron leakage is further suppressed.

[0078] (Embodiment 3) Figure 9 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element including the active layer according to Embodiment 3. The semiconductor light-emitting element 100B according to Embodiment 3 has a configuration in which the P-side SCH portion 5A of the semiconductor light-emitting element 100A according to Embodiment 2 is replaced with the P-side SCH portion 5B. Therefore, the P-side SCH portion 5B will be described mainly below, and the description of other components will be omitted as appropriate. In Figure 9, line L13 indicates the energy level at the upper end of the valence band, and line L14 indicates the energy level at the lower end of the conduction band.

[0079] The P-side SCH portion 5B of the semiconductor light-emitting element 100B includes a plurality of P-side SCH layers, namely P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd. All of the P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd are AlInAsP layers. In this embodiment, the compositions of the P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd are, respectively, Al ０．５２ In As, Al ０．４５ In As ０．８５ P, Al ０．２１ In As ０．５ P, Al ０．１１ In As ０．３ It is P. Furthermore, the P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd are not intentionally doped with impurities.

[0080] Table 3 shows the composition and thickness of each layer shown in Figure 9, and the strain relative to InP. As can be seen from Table 3, the P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd are arranged such that the Al composition ratio and As composition ratio gradually increase as they approach the active layer 4.

[0081] As shown in Figure 9, in the P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd, the valence band upper energy, indicated by line L11, increases stepwise as you approach the active layer 4.

[0082] Furthermore, as shown in Table 3, the P-side SCH layers 5Ba and 5Bb have lattice constants smaller than those of InP and have an extensional strain of -0.3%. In contrast, the P-side SCH layers 5Bc and 5Bd have lattice constants larger than those of InP and have an extensional strain of 0.2%. In this case as well, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd and the lattice constant of InP to the lattice constant of InP is within ±0.3%. Specifically, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Ba, 5Bb, 5Bc, and 5Bd and the lattice constant of InP to the lattice constant of InP is 0% (= (-0.3 × 10 - 0.3 × 10 + 0.2 × 15 + 0.2 × 15) / (10 + 10 + 15 + 15).

[0083] In the semiconductor light-emitting element 100B configured as described above, the same effects as those of the semiconductor light-emitting element 100B can be obtained. Furthermore, in the semiconductor light-emitting element 100B, a P-side SCH portion 5B with a film thickness-weighted average strain of 0% is realized by combining P-side SCH layers 5Ba and 5Bb having a lattice constant smaller than that of InP, and P-side SCH layers 5Bc and 5Bd having a lattice constant larger than that of InP. In this case, it is relatively easy to form a P-side SCH portion 5B with high crystal quality in a thicker form.

[0084] (Embodiment 4) Figure 10 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element according to Embodiment 4, including the active layer. The semiconductor light-emitting element 100C according to Embodiment 4 has a configuration in which the P-side SCH portion 5 of the semiconductor light-emitting element 100 according to Embodiment 1 is replaced with a P-side SCH portion 5C. Therefore, the P-side SCH portion 5C will be described below, and the description of other components will be omitted as appropriate. In Figure 10, line L15 indicates the energy level at the upper end of the valence band, and line L16 indicates the energy level at the lower end of the conduction band.

[0085] The P-side SCH portion 5C of the semiconductor light-emitting element 100C includes a plurality of P-side SCH layers, namely P-side SCH layers 5Ca, 5Cb, 5Cc, and 5Cd. All of the P-side SCH layers 5Ca, 5Cb, 5Cc, and 5Cd are AlInAsP layers. In this embodiment, the compositions of the P-side SCH layers 5Ca, 5Cb, 5Cc, and 5Cd are, respectively, Al ０．３８ In As ０．８ P, Al ０．３８ In As ０．７７ P, Al ０．３８ In As ０．７４ P, Al ０．３８ In As ０．７１ It is P. Furthermore, the P-side SCH layer 5Ca, 5Cb, 5Cc, and 5Cd are not intentionally doped with impurities.

[0086] Table 4 shows the composition and thickness of each layer shown in Figure 10, and the strain relative to InP. As can be seen from Table 4, the P-side SCH layers 5Ca, 5Cb, 5Cc, and 5Cd have the same Al composition ratio, and are arranged so that the As composition ratio increases in stages as it approaches the active layer 4.

[0087] As shown in Figure 10, in the P-side SCH layers 5Ca, 5Cb, 5Cc, and 5Cd, the valence band upper energy, indicated by line L15, increases stepwise as you approach the active layer 4.

[0088] Furthermore, as can be seen from Table 4, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Ca, 5Cb, 5Cc, and 5Cd and the lattice constant of InP, relative to the lattice constant of InP, is within ±0.3%. Specifically, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Ca, 5Cb, 5Cc, and 5Cd and the lattice constant of InP, relative to the lattice constant of InP, is -0.17% (= (-0.1 × 10 - 0.2 × 15 - 0.3 × 15) / (10 + 10 + 15 + 15).

[0089] With the semiconductor light-emitting element 100C configured as described above, the same effects as those of the semiconductor light-emitting element 100 can be obtained.

[0090] (Embodiment 5) Figure 11 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element including the active layer according to Embodiment 5. The semiconductor light-emitting element 100D according to Embodiment 5 has a configuration in which the P-side SCH portion 5 of the semiconductor light-emitting element 100 according to Embodiment 1 is replaced with a P-side SCH portion 5D. Therefore, the P-side SCH portion 5D will be described below, and the description of other components will be omitted as appropriate. In Figure 11, line L17 indicates the energy level at the upper end of the valence band, and line L18 indicates the energy level at the lower end of the conduction band.

[0091] The P-side SCH portion 5D of the semiconductor light-emitting element 100D includes a plurality of P-side SCH layers, namely P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd. All of the P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd are AlInAsP layers. In this embodiment, the compositions of the P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd are, respectively, Al ０．３８ In As ０．８ P, Al ０．３９ In As ０．８ P, Al ０．４１ In As ０．８ P, Al ０．４２In As ０．８ It is P. Furthermore, the P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd are not intentionally doped with impurities.

[0092] Table 5 shows the composition and thickness of each layer shown in Figure 11, and the strain relative to InP. As can be seen from Table 5, the P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd have the same As composition ratio, and are arranged so that the Al composition ratio decreases in stages as they approach the active layer 4.

[0093] As shown in Figure 11, in the P-side SCH layers 5Ea, 5Eb, 5Ec, and 5Ed, the valence band upper energy, indicated by line L17, increases stepwise as you approach the active layer 4.

[0094] Furthermore, as can be seen from Table 5, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd and the lattice constant of InP to the lattice constant of InP is within ±0.3%. Specifically, the ratio of the difference between the film thickness-weighted average of the lattice constants of the P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd and the lattice constant of InP to the lattice constant of InP is -0.17% (= (-0.1 × 10 - 0.2 × 15 - 0.3 × 15) / (10 + 10 + 15 + 15).

[0095] As described above, the semiconductor light-emitting element 100D can achieve the same effects as the semiconductor light-emitting element 100. Furthermore, in the semiconductor light-emitting element 100D, since the composition of the group V element As is the same in the P-side SCH layers 5Da, 5Db, 5Dc, and 5Dd, the adjustment of the As composition conditions during manufacturing can be made simpler. As a result, the semiconductor light-emitting element 100D is easier to manufacture.

[0096] (Embodiment 6) Figure 12 is a diagram showing an example of the structure and energy band of the portion of the semiconductor light-emitting element including the active layer according to Embodiment 6. The semiconductor light-emitting element 100E according to Embodiment 6 has a configuration in which the P-side SCH portion 5 of the semiconductor light-emitting element 100 according to Embodiment 1 is replaced with a P-side SCH portion 5E. Therefore, the P-side SCH portion 5E will be described mainly below, and the description of other components will be omitted as appropriate. In Figure 12, line L19 indicates the energy level at the upper end of the valence band, and line L20 indicates the energy level at the lower end of the conduction band.

[0097] The P-side SCH portion 5E of the semiconductor light-emitting element 100E includes a plurality of P-side SCH layers, namely P-side SCH layers 5Ea, 5Eb, 5Ec, and 5Ed. Of these layers, the P-side SCH layers 5Ea and 5Eb, located adjacent to the active layer 4, are both AlInAsP layers made of AlInAsP. The P-side SCH layers 5Ec and 5Ed, located spaced apart from the active layer 4, are both GaInAsP layers made of GaInAsP. In this embodiment, the compositions of the P-side SCH layers 5Ea, 5Eb, 5Ec, and 5Ed are, respectively, Al ０．３８ In As ０．８ P, Al ０．３３ In As ０．７ P, Ga ０．０９ In As ０．２ P, Ga ０．０５ In As ０．１ It is P. Furthermore, the P-side SCH layers 5Ea, 5Eb, 5Ec, and 5Ed are not intentionally doped with impurities.

[0098] Table 6 shows the composition and thickness of each layer shown in Figure 12, and the strain with respect to InP.

[0099] As shown in Figure 12, in the P-side SCH layers 5Ea, 5Eb, 5Ec, and 5Ed, the valence band upper energy, indicated by line L19, increases stepwise as you approach the active layer 4.

[0100] Furthermore, as can be seen from Table 6, the P-side SCH layers 5Ea, 5Eb, 5Ec, and 5Ed have the same lattice constant as InP, so the ratio of the difference between the film thickness-weighted average of these lattice constants and the lattice constant of InP to the lattice constant of InP is within ±0.3%.

[0101] In the semiconductor light-emitting element 100E configured as described above, the P-side SCH portion 5E includes a GaInAsP layer, but the same effects as the semiconductor light-emitting element 100 can be obtained.

[0102] [Effects of P-type impurities] In each of the above embodiments, the P-side SCH layer is not intentionally doped with impurities. However, the P-side SCH layer may contain P-type impurities. When the P-side SCH layer contains P-type impurities, the band offset in the conduction band can be increased.

[0103] For example, Figure 13 shows a modified example of Embodiment 1, in which the P-side SCH layers 5a, 5b, 5c, and 5d of the semiconductor light-emitting element 100 according to Embodiment 1 contain 8.0 × 10⁻¹⁴ p-type impurities. １７ cm －３ This figure shows the case when a voltage is applied when the material is doped with the specified concentration. In Figure 13, a voltage of 0.95 V is applied between the N-side electrode 1 and the P-side electrode 10. In Figure 13, line L21 indicates the energy level at the lower end of the valence band, and line L22 indicates the energy level at the upper end of the conduction band. On the other hand, L23 and L24 correspond to lines L5 and L6 in Figure 3, and represent the semiconductor light-emitting element 100 according to Embodiment 1. As can be seen from Figure 13, in the modified case, the band offset becomes even larger as indicated by the arrow Ar2, which is preferable from the viewpoint of suppressing electron leakage.

[0104] However, if the P-side SCH layer is excessively doped with P-type impurities, the light absorption due to P-type impurities may increase, so the concentration of P-type impurities should be 8.0 × 10⁻⁶. １７ cm －３ The following are preferable.

[0105] (Embodiment 7) In the above embodiment, the active layer includes a type II heterojunction structure, but the active layer does not have to include a type II heterojunction structure. For example, the active layer may include a type I heterojunction structure formed by a quantum well layer and a barrier layer.

[0106] Figure 14 shows the relationship between the lower conduction band energy and the upper valence band energy of a lattice-matched mixed crystal with an InP substrate. It differs from Figure 4 in that black circles indicate an example of the coordinate points of the quantum well layer, and white circles indicate an example of the coordinate points of the barrier layer. Note that in Figure 14, the well layer is Ga ０．２２ In As ０．５４ It is P, and the barrier layer has a different composition from the quantum well layer. ０．１４ In As ０．２９ It is P.

[0107] Region A3 represents a desirable range for the P-side SCH layer in the type I heterojunction structure formed by the quantum well layer and the barrier layer described above. The desirable range for the P-side SCH layer is a range in which the conduction band lower edge energy is higher than the conduction band lower edge energy of the barrier layer, and the valence band upper edge energy is between the valence band upper edge energy of the cladding layer (P-type semiconductor layer) and the valence band upper edge energy of the barrier layer. The barrier layer is the layer adjacent to the P-side SCH layer in the active layer.

[0108] Similar to the type I heterojunction structure, AlInAsP has a conduction band lower edge energy higher than that of the barrier layer, and its valence band upper edge energy is between the valence band upper edge energy of the cladding layer and the valence band upper edge energy of the barrier layer. Therefore, it is suitable as a P-side SCH layer.

[0109] Figure 15 shows an example of the structure and energy band of the portion of the semiconductor light-emitting element including the active layer according to Embodiment 7. The semiconductor light-emitting element 100A according to Embodiment 7 has a configuration in which the active layer 4 of the semiconductor light-emitting element 100 according to Embodiment 1 is replaced with an active layer 4F, and the P-side SCH portion 5 is replaced with a P-side SCH portion 5E. Therefore, the following will mainly describe the active layer 4F and the P-side SCH portion 5A, and the description of other components will be omitted as appropriate. In Figure 15, line L23 indicates the energy level at the upper end of the valence band, and line L24 indicates the energy level at the lower end of the conduction band.

[0110] The active layer 4F has a structure in which the barrier layer 4Fd, quantum well layer 4Fe, and barrier layer 4Ff are arranged in this order in the stacking direction. The quantum well layer 4Fe is made of, for example, GaInAsP. The composition of the quantum well layer 4Fe in this embodiment is Ga ０．１１ In As ０．５４ It is P. The barrier layers 4Fd and 4Ff are made of GaInAsP having a different composition from the quantum well layer, for example. The composition of the barrier layers 4Fd and 4Ff in this embodiment is Ga ０．１４ In As ０．２９ The particle is P. The barrier layer 4Fd, the quantum well layer 4Fe, and the barrier layer 4Ff form a type I heterojunction structure. As a result, in the active layer 4F, electrons and holes are confined to the quantum well layer 4Fe.

[0111] The P-side SCH portion 5F includes a plurality of P-side SCH layers, namely P-side SCH layers 5Fa, 5Fb, 5Fc, and 5Fd. All of the P-side SCH layers 5Fa, 5Fb, 5Fc, and 5Fd are AlInAsP layers. In this embodiment, the compositions of the P-side SCH layers 5Fa, 5Fb, 5Fc, and 5Fd are, respectively, Al ０．３８ In As ０．８ P, Al ０．３３ In As ０．７ P, Al ０．２８ In As ０．６ P, Al ０．２５ In As ０．５３It is P. The P-side SCH layers 5Fa, 5Fb, 5Fc, and 5Fd have the same lattice constant as that of InP. Therefore, the ratio of the difference between the weighted average film thickness of these lattice constants and the lattice constant of InP to the lattice constant of InP for the P-side SCH layers 5Fa, 5Fb, 5Fc, and 5Fd is within the range of ±0.3%. Also, the P-side SCH layers 5Fa, 5Fb, 5Fc, and 5Fd are not intentionally doped with impurities and are, for example, i-type semiconductors.

[0112] Table 7 shows the composition and layer thickness of each layer shown in FIG. 15. As can be seen from Table 7, the P-side SCH layers 5a, 5b, 5c, and 5d are arranged such that the Al composition ratio and the As composition ratio gradually increase as they approach the active layer 4.

[0113] Here, as shown in FIG. 15, in the P-side SCH layers 5Fa, 5Fb, 5Fc, and 5Fd, as approaching the active layer 4, the valence band top energy shown by the line L23 gradually increases.

[0114] The semiconductor light-emitting device 100F configured as described above has an active layer 4F including a type-I heterojunction structure, and the same effects as those of the semiconductor light-emitting device 100 can be obtained.

[0115] In FIG. 15, as a comparative form, the P-side SCH portion 5F in the semiconductor light-emitting device 100F is replaced with Ga ０．１３ InAs ０．２８ P with a layer thickness of 10 nm, Ga ０．０９ InAs ０．２１ P layer, Ga with a layer thickness of 15 nm ０．０６ InAs ０．１３ P with a layer thickness of 15 nm, Ga ０．０２ InAs ０．０５ P is shown. The dashed line L25 indicates the energy level of the valence band bottom, and the dashed line L26 indicates the energy level of the conduction band top. When the P-side SCH portion is made of GaInAsP, as shown by the line L25, the formation of a high barrier for holes is suppressed, but as shown by the line L26, the band offset with the barrier layer 4Fd in the conduction band is small.

[0116] In the above embodiment, the valence band upper energy in the P-side SCH portion increases stepwise as it approaches the active layer, but it may increase continuously depending on the gradient composition.

[0117] Furthermore, in the above embodiment, the substrate is made of N-type InP, but it may also be made of P-type InP. In the case of a substrate made of P-type InP, the stacking order of the P-type semiconductor layer and the N-type semiconductor layer relative to the active layer is the reverse of that in Figure 1.

[0118] Furthermore, in embodiments 1 to 7 described above, since the active layer is a so-called W-type type II heterojunction structure, the layer adjacent to the P-side SCH layer in the active layer is an electron well layer. However, if the active layer is a so-called M-type type II heterojunction structure, the layer adjacent to the P-side SCH layer in the active layer is a hole well layer. Thus, when the active layer is a type II heterojunction structure, the layer adjacent to the P-side SCH layer in the active layer differs depending on the structure.

[0119] Furthermore, in the above embodiment, the semiconductor light-emitting element is configured as a semiconductor laser element, but the semiconductor light-emitting element may also be configured as a semiconductor optical amplifier. When configured as a semiconductor optical amplifier, the semiconductor light-emitting element is configured without a laser resonator. Also, when the semiconductor light-emitting element is configured as a distributed feedback (DFB) laser element, a diffraction grating layer is provided near the active layer. Also, when the semiconductor light-emitting element is configured as a surface-emitting laser element, the active layer is placed inside a vertical laser resonator.

[0120] Furthermore, the present invention is not limited by the embodiments described above. Configurations that appropriately combine the above-described components are also included in the present invention. Moreover, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the embodiments described above, and various modifications are possible.

[0121] This invention can be used in semiconductor light-emitting devices.

[0122] 1: N-side electrode 2: N-type semiconductor section 2a: Substrate 2b: N-type cladding layer 3: N-side SCH layer (N-side isolated confinement heterostructure layer) 4, 4F: Active layer 4a, 4Aa, 4Ac, 4c: Electron well layer 4b: Hole well layer 4Fd, 4Ff: Barrier layer 4Fe: Quantum well layer 5, 5A, 5B, 5C, 5D, 5E, 5F: P-side SCH section 5a, 5Aa, 5Ab, 5Ac, 5Ad, 5b, 5Ba, 5Bb, 5Bc, 5Bd, 5c, 5Ca, 5Cb, 5Cc, 5Cd, 5d, 5Da, 5Db, 5Dc, 5Dd, 5Ea, 5Eb, 5Ec, 5Ed, 5Fa, 5Fb, 5Fc, 5Fd: P-side SCH layer 6: P-type semiconductor section 6a, 6b, 6c: Semiconductor layer 7: Guide layer 8, 8a, 8b: Current blocking layer 9: Contact layer 10: P-side electrode 100, 100A, 100B, 100C, 100D, 100E, 100F: Semiconductor light-emitting element A1, A2, A3: Region Ar1, Ar2: Arrow L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14, L15, L16, L17, L18, L19, L20, L21, L22, L23, L24, L25, L26: Line

Claims

1. A semiconductor light-emitting element comprising: a substrate made of InP; an active layer located on the substrate; a plurality of P-side isolated-confinement heterostructure layers located adjacent to the active layer; an N-side isolated-confinement heterostructure layer located adjacent to the active layer on the opposite side of the plurality of P-side isolated-confinement heterostructures; a P-type semiconductor layer located adjacent to the plurality of P-side isolated-confinement heterostructures on the opposite side of the active layer; and an N-type semiconductor layer located adjacent to the N-side isolated-confinement heterostructure layer on the opposite side of the active layer, wherein the plurality of P-side isolated-confinement heterostructure layers include a plurality of AlInAsP layers in which the ratio of the difference between the film thickness weighted average of their lattice constants and the lattice constant of InP to the lattice constant of InP is within ±0.3%; and in the plurality of P-side isolated-confinement heterostructure layers, the valence band upper edge energy increases stepwise or continuously as it approaches the active layer.

2. The semiconductor light-emitting element according to claim 1, wherein the valence band upper energy of the P-side isolated confinement heterostructure layer is the energy between the valence band upper energy of the P-type semiconductor layer and the valence band upper energy of the layer adjacent to the P-side isolated confinement heterostructure layer in the active layer.

3. The semiconductor light-emitting element according to claim 2, wherein the AlInAsP layer has a conduction band lower energy greater than the conduction band lower energy of the P-type semiconductor layer.

4. The semiconductor light-emitting element according to claim 3, wherein the plurality of AlInAsP layers include AlInAsP layers having a band gap larger than the band gap of the P-type semiconductor layer.

5. The semiconductor light-emitting element according to claim 3, wherein the plurality of AlInAsP layers have the same lattice constant as InP, and are arranged such that the Al composition ratio and As composition ratio increase stepwise or continuously as they approach the active layer.

6. The semiconductor light-emitting element according to claim 5, wherein the Al composition ratio is 0 or more and 0.48 or less.

7. The semiconductor light-emitting element according to claim 6, wherein the Al composition ratio is 0.2 or more and 0.48 or less.

8. The semiconductor light-emitting element according to claim 5, wherein the plurality of AlInAsP layers include AlInAsP layers having a lattice constant smaller than that of InP.

9. The semiconductor light-emitting element according to claim 8, wherein the ratio of the difference between the lattice constant of the AlInAsP layer having a lattice constant smaller than that of InP and the lattice constant of InP to the lattice constant of InP is -0.3% or less.

10. The semiconductor light-emitting element according to claim 8, wherein the plurality of AlInAsP layers include AlInAsP layers having a lattice constant greater than that of InP.

11. The semiconductor light-emitting element according to claim 3, wherein the plurality of AlInAsP layers have the same Al composition ratio and are arranged such that the As composition ratio increases stepwise or continuously as it approaches the active layer.

12. The semiconductor light-emitting element according to claim 3, wherein the plurality of AlInAsP layers have the same As composition ratio and are arranged such that the Al composition ratio decreases stepwise or continuously as it approaches the active layer.

13. The semiconductor light-emitting element according to claim 3, wherein the plurality of P-side isolated confinement heterostructure layers include a GaInAsP layer.

14. The semiconductor light-emitting element according to claim 1, wherein the P-side isolated confinement heterostructure layer is not intentionally doped with impurities.

15. The P-side separated confinement heterostructure layer is 8.0 × 10 １７ cm －３ The semiconductor light-emitting element according to claim 1, wherein the element is doped with P-type impurities at the following concentrations.

16. The semiconductor light-emitting element according to claim 3, wherein the active layer comprises a type II heterojunction structure formed by a hole quantum well layer made of AlGaInAs and an electron quantum well layer made of GaInAsP.

17. The semiconductor light-emitting element according to claim 16, wherein the valence band upper energy of the P-side separated confinement heterostructure layer is the energy between the valence band upper energy of the P-type semiconductor layer and the valence band upper energy of the electron quantum well layer.

18. The semiconductor light-emitting element according to claim 3, wherein the active layer comprises a type I heterojunction structure formed by a quantum well layer made of GaInAsP and a barrier layer made of GaInAsP having a composition different from that of the quantum well layer.

19. The semiconductor light-emitting element according to claim 18, wherein the valence band upper energy of the P-side separated confinement heterostructure layer is the energy between the valence band upper energy of the P-type semiconductor layer and the valence band upper energy of the barrier layer.

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