Semiconductor photodetector

Abstract

To provide a semiconductor light-receiving element having high quantum efficiency in wavelengths close to an absorption edge wavelength.SOLUTION: A semiconductor light-receiving element comprises: an indium-phosphorous substrate; a first group III-V compound semiconductor layer of a first conductivity type, a second group III-V compound semiconductor layer of a second conductivity type, and a light absorption layer provided between the first group III-V compound semiconductor layer and the second group III-V compound semiconductor layer. The first group III-V compound semiconductor layer is provided between the indium-phosphorous substrate and the light absorption layer. The light absorption layer has a superlattice structure of type II. The superlattice structure includes a gallium indium arsenide layer and a gallium arsenide antimony layer. The gallium indium arsenide layer has compressive distortion. The gallium arsenide antimony layer has tensile distortion.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to a semiconductor photodetector. [Background technology]

[0002] Non-patent document 1 discloses a pin photodiode having a strain-compensated type II superlattice structure on an n-type indium phosphide (InP) substrate. The superlattice structure includes a gallium indium arsenide (GaInAs) layer and a gallium arsenide antimony (GaAsSb) layer. The GaInAs layer has tensile strain. The GaAsSb layer has compressive strain.

[0003] Non-patent document 2 discloses a pin photodiode having a strain-compensated type II superlattice structure on an n-type InP substrate. The superlattice structure includes a GaInAs layer and a GaAsSb layer. The GaInAs layer has tensile strain. The GaAsSb layer has compressive strain. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Baile Chen, et al, "SWIR / MWIRInP-Based pin Photodiodes with InGaAs / GaAsSb Type-II Quantum Wells" IEEEJOURNAL OF QUANTUM ELECTRONICS, VOL. 47, NO. 9, SEPTEMBER 2011 [Non-Patent Document 2] K. Sugimura, et al,"High-performance extended SWIR photodetectors using strain compensatedInGaAs / GaAsSb type-II quantum wells" Proc. SPIE 10926, Quantum Sensing andNano Electronics and Photonics XVI, 109260E (1 February 2019); doi:10.1117 / 12.2509148 [Overview of the project] [Problems that the invention aims to solve]

[0005] When the GaInAs layer has tensile strain and the GaAsSb layer has compressive strain, the quantum efficiency may decrease at wavelengths close to the absorption edge wavelength.

[0006] This disclosure provides a semiconductor photodetector having high quantum efficiency at wavelengths close to the absorption edge wavelength. [Means for solving the problem]

[0007] A semiconductor photodetector according to one aspect of the present disclosure comprises an indium phosphide substrate, a first III-V compound semiconductor layer of a first conductivity type, a second III-V compound semiconductor layer of a second conductivity type, and a light-absorbing layer provided between the first III-V compound semiconductor layer and the second III-V compound semiconductor layer, wherein the first III-V compound semiconductor layer is provided between the indium phosphide substrate and the light-absorbing layer, the light-absorbing layer has a type II superlattice structure, the superlattice structure includes a gallium indium arsenide layer and a gallium arsenide antimony layer, the gallium indium arsenide layer has compressive strain, and the gallium arsenide antimony layer has tensile strain. [Effects of the Invention]

[0008] According to this disclosure, a semiconductor photodetector having high quantum efficiency at wavelengths close to the absorption edge wavelength is provided. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing a semiconductor photodetector according to one embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing the light-absorbing layer included in the semiconductor photodetector shown in Figure 1. [Figure 3] Figure 3 is a graph showing examples of combinations of gallium composition x in the GaxIn1-xAs layer and arsenic composition y in the GaAsySb1-y layer. [Figure 4] Figure 4 is a graph showing examples of the relationship between the quantum efficiency of semiconductor photodetectors and wavelength in the first to third experiments. [Figure 5] Figure 5 is a graph showing an example of the energy band diagram for the semiconductor photodetector in the first experiment. [Figure 6] Figure 6 is a graph showing an example of the energy band diagram for a semiconductor photodetector in the second experiment. [Figure 7] Figure 7 is a graph showing an example of the energy band diagram for a semiconductor photodetector in the third experiment. [Figure 8] Figure 8 is a graph showing an example of the relationship between the quantum efficiency of the semiconductor photodetector and wavelength in the fourth experiment. [Modes for carrying out the invention]

[0010] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure will be listed and described.

[0011] (1) The semiconductor photodetector comprises an indium phosphide substrate, a first III-V compound semiconductor layer of a first conductivity type, a second III-V compound semiconductor layer of a second conductivity type, and a light-absorbing layer provided between the first III-V compound semiconductor layer and the second III-V compound semiconductor layer, wherein the first III-V compound semiconductor layer is provided between the indium phosphide substrate and the light-absorbing layer, the light-absorbing layer has a type II superlattice structure, the superlattice structure includes a gallium indium arsenide layer and a gallium arsenide antimony layer, the gallium indium arsenide layer has compressive strain, and the gallium arsenide antimony layer has tensile strain.

[0012] According to the above semiconductor photodetector, high quantum efficiency can be obtained at wavelengths close to the absorption edge wavelength.

[0013] (2) In the above (1), the gallium composition x of the gallium indium arsenide layer may be 0.17 or greater.

[0014] In this case, the absolute value of the strain ε in the gallium indium arsenide layer becomes 2% or less, thus reducing the number of lattice defects.

[0015] (3) In (1) or (2) above, the arsenic composition y of the gallium arsenide antimony layer may be 0.78 or less.

[0016] In this case, the absolute value of the strain ε in the gallium arsenide antimony layer becomes 2% or less, thus reducing the number of lattice defects.

[0017] (4) In any one of (1) to (3) above, the gallium composition x of the gallium indium arsenide layer may be 0.46 or less.

[0018] (5) In any one of (1) to (4) above, the arsenic composition y of the gallium arsenide antimony layer may be 0.52 or greater.

[0019] (6) In any one of (1) to (5) above, the gallium indium arsenide layer may contain n gallium indium arsenide monolayers, and the gallium arsenide antimony layer may contain m gallium arsenide antimony monolayers, and n and m may be integers between 13 and 25.

[0020] (7) In any one of (1) to (6) above, when the gallium composition of the gallium indium arsenide layer is x and the arsenide composition of the gallium arsenide antimony layer is y, y ≤ 1.054x 2 -2.809x+1.594 It may satisfy the requirement.

[0021] In this case, the strain throughout the entire light-absorbing layer can be reduced. If the gallium indium arsenide layer contains 25 monolayers of gallium indium arsenide and the gallium arsenide antimony layer contains 13 monolayers of gallium arsenide antimony, then the strain throughout the entire light-absorbing layer becomes zero when the equality in the above equation holds.

[0022] (8) In any one of (1) to (7) above, when the gallium composition of the gallium indium arsenide layer is x and the arsenide composition of the gallium arsenide antimony layer is y, y≧0.137x 2 -0.627x+0.775 It may satisfy the requirement.

[0023] In this case, the strain throughout the entire light-absorbing layer can be reduced. If the gallium indium arsenide layer contains 13 monolayers of gallium indium arsenide and the gallium arsenide antimony layer contains 25 monolayers of gallium arsenide antimony, then the strain throughout the entire light-absorbing layer becomes zero when the equality in the above equation holds.

[0024] [Details of the embodiments of this disclosure] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. In the description of the drawings, the same reference numerals are used for identical or equivalent elements, and redundant descriptions are omitted.

[0025] FIG. 1 is a cross-sectional view schematically showing a semiconductor light receiving element according to an embodiment. FIG. 2 is a cross-sectional view schematically showing a light absorption layer included in the semiconductor light receiving element of FIG. 1. The semiconductor light receiving element 100 shown in FIG. 1 is, for example, a photodiode. The semiconductor light receiving element 100 includes an indium phosphide (InP) substrate 10, an n-type (first conductivity type) first III-V compound semiconductor layer 12, a p-type (second conductivity type) second III-V compound semiconductor layer 14, and a light absorption layer 16. The light absorption layer 16 is provided between the first III-V compound semiconductor layer 12 and the second III-V compound semiconductor layer 14.

[0026] The InP substrate 10 may be a semi-insulating substrate or an n-type substrate. The first III-V compound semiconductor layer 12 may be provided between the main surface of the InP substrate 10 and the light absorption layer 16. The main surface of the InP substrate 10 may be a (100) surface.

[0027] The first III-V compound semiconductor layer 12 may be an n-type gallium indium arsenide (Ga x1 In 1-x1 As or GaInAs) layer. x1 is the gallium (Ga) composition. x1 is greater than 0 and less than 1. x1 may be from 0.46 to 0.48. The n-type dopant concentration in the first III-V compound semiconductor layer 12 is 5×10 17 to 3×10 19 cm -3 and may be. The thickness of the first III-V compound semiconductor layer 12 may be from 0.2 to 3 μm.

[0028] The second III-V compound semiconductor layer 14 may be a p-type gallium indium arsenide (Ga x2 In 1-x2 As or GaInAs) layer. x2 is the gallium (Ga) composition. x2 is greater than 0 and less than 1. x2 may be from 0.46 to 0.48. The p-type dopant concentration in the second III-V compound semiconductor layer 14 is 5×10 17 to 3×10 19 cm -3The thickness of the second III-V compound semiconductor layer 14 may be 0.2 to 3 μm.

[0029] The light-absorbing layer 16 may be an undoped III-V compound semiconductor layer. In this specification, "undoped" means that dopants are not intentionally applied. Therefore, an "undoped" III-V compound semiconductor layer has a density of 1 × 10⁻⁶ 15 cm -3 It may have a p-type dopant concentration of less than 1 × 10⁻⁶. 15 cm -3 It may have an n-type dopant concentration of less than 100%. The light-absorbing layer 16 has a type II superlattice structure.

[0030] As shown in Figure 2, the superlattice structure of the light-absorbing layer 16 is gallium indium arsenide (Ga x In 1-x As or GaInAs) layer L1 and gallium arsenide antimony (GaAs y S 1-y Alternatively, it may include a GaAsSb) layer L2. x In 1-x As layer L1 and GaAs y S 1-y Each layer L2 may be an undoped layer.

[0031] Ga x In 1-x The As layer L1 has compressive strain. x is the gallium (Ga) composition. The Ga composition x is greater than 0 and less than 0.468. If the Ga composition x is less than 0.468, Ga x In 1-x As layer L1 has compressive strain. x In 1-x The Ga composition x of the As layer L1 may be 0.17 or higher, or 0.46 or lower. If the Ga composition x is 0.17 or higher, x In 1-x The absolute value of the strain ε in the As layer L1 becomes 2% or less. As a result, Ga x In 1-x The lattice defects in the As layer L1 can be reduced. x In1-x The As layer L1 contains n Ga x In 1-x It may contain an As monolayer. n may be an integer between 13 and 25. x In 1-x The thickness of the As layer L1 may be 3 to 8 nm.

[0032] GaAs y S 1-y Layer L2 has tensile strain. y is the arsenic (As) composition. The As composition y is greater than 0.512 and less than 1. If the As composition y is greater than 0.512, GaAs y S 1-y Layer L2 has tensile strain. GaAs y S 1-y The As composition y of layer L2 may be 0.52 or higher, or 0.78 or lower. If the As composition y is 0.78 or lower, GaAs y S 1-y The absolute value of the strain ε in layer L2 becomes 2% or less. As a result, GaAs y S 1-y This can reduce lattice defects in layer L2. GaAs y S 1-y Layer L2 contains m GaAs y S 1-y It may contain a monolayer. m may be an integer between 13 and 25. m may be the same as or different from n. GaAs y S 1-y The thickness of layer L2 may be 3 to 8 nm. GaAs y S 1-y The thickness of layer L2 is Ga x In 1-x The thickness of the As layer L1 may be the same as or different from that of the As layer.

[0033] Ga x In 1-x As layer L1 or GaAs y S 1-y The strain ε of layer L2 is calculated by the following equation (1). ε = (a1 - a2) / a2 …(1) In equation (1), a1 is the lattice constant of the InP substrate. a2 is the Ga in the unstressed state. x In 1-x As or GaAs y S 1-y This is the lattice constant.

[0034] When the Ga composition is x and the As composition is y, At least one of the following equations (2) and (3) may be satisfied. y ≤ 1.054x 2 -2.809x + 1.594 …(2) y≧0.137x 2 -0.627x + 0.775 …(3)

[0035] When n is 25 and m is 13, if the equality in equation (2) above holds, the strain in the entire light-absorbing layer 16 becomes zero. When n is 13 and m is 25, if the equality in equation (3) above holds, the strain in the entire light-absorbing layer 16 becomes zero.

[0036] Ga x In 1-x As layer L1 and GaAs y S 1-y The layers L2 may be arranged alternately along the first direction D1. On the lower surface of the light-absorbing layer 16 closest to the first III-V compound semiconductor layer 12, Ga x In 1-x An As layer L1 may be located on the semiconductor layer. x In 1-x The As layer L1 can be formed with good crystallinity. On the upper surface of the light absorption layer 16 closest to the second III-V compound semiconductor layer 14, GaAs y S 1-y Layer L2 may be located. This allows GaAs y S 1-y A semiconductor layer can be formed on layer L2 with good crystallinity. x In 1-x As layer L1 and GaAs y S 1-y The number of pairs (period) in layer L2 may be between 200 and 400.

[0037] As shown in Figure 1, the semiconductor photodetector 100 may further include an n-type III-V compound semiconductor layer 20. The III-V compound semiconductor layer 20 is provided between the InP substrate 10 and the first III-V compound semiconductor layer 12. The III-V compound semiconductor layer 20 may also be a contact layer. The III-V compound semiconductor layer 20 has a higher n-type dopant concentration than the n-type dopant concentration of the first III-V compound semiconductor layer 12. The III-V compound semiconductor layer 20 may also be a GaInAs layer. An electrode 30 may be connected to the III-V compound semiconductor layer 20.

[0038] The semiconductor photodetector 100 may further include a p-type III-V compound semiconductor layer 22. The second III-V compound semiconductor layer 14 is provided between the III-V compound semiconductor layer 22 and the light absorption layer 16. The III-V compound semiconductor layer 22 may also be a contact layer. The III-V compound semiconductor layer 22 has a p-type dopant concentration higher than that of the second III-V compound semiconductor layer 14. The III-V compound semiconductor layer 22 may also be a GaInAs layer. An electrode 40 may be connected to the III-V compound semiconductor layer 22.

[0039] The InP substrate 10, the III-V compound semiconductor layer 20, the first III-V compound semiconductor layer 12, the light absorption layer 16, the second III-V compound semiconductor layer 14, and the III-V compound semiconductor layer 22 may be arranged in this order along a first direction D1. The first direction D1 may be perpendicular to the main surface of the InP substrate 10. The first direction D1 may be the thickness direction of the light absorption layer 16. The first direction D1 may be the direction from the first III-V compound semiconductor layer 12 toward the second III-V compound semiconductor layer 14. The first direction D1 may be the crystal growth direction.

[0040] The semiconductor light-receiving element 100 can detect incident light L. The incident light L may be visible light or infrared light having a wavelength of 0.4 to 4 μm. The incident light L may travel in the first direction D1. The incident light L may enter the light absorption layer 16 through the InP substrate 10. The semiconductor light-receiving element 100 may have an absorption edge wavelength (cutoff wavelength) of 2 to 4 μm, or may have an absorption edge wavelength of 2.5 to 4 μm. The semiconductor light-receiving element 100 can be used in a spectroscopic system, an imaging system, or an optical communication system of a gas analyzer.

[0041] FIG. 3 is a graph showing an example of the combination of the Ga composition x of the Ga x In 1-x As layer L1 and the As composition y of the GaAs y Sb 1-y layer L2. In FIG. 3, the (x, y) coordinates from point A to point E are as follows. A(0.335, 0.772) B(0.460, 0.525) C(0.441, 0.525) D(0.172, 0.671) E(0.172, 0.772)

[0042] Ga x In 1-x The combination of the Ga composition x of the GaAs layer L1 and the As composition y of the GaAs y Sb 1-y layer L2 may be located within the region AR surrounded by points A to E. That is, the Ga composition x may be 0.17 or more and 0.46 or less, the As composition y may be 0.52 or more and 0.78 or less, and both of the above formulas (2) and (3) may be satisfied.

[0043] According to the semiconductor light-receiving element 100, a high quantum efficiency can be obtained at a wavelength close to the absorption edge wavelength. The mechanism for obtaining a high quantum efficiency is considered as follows, but is not limited thereto.

[0044] Ga x In 1-x The As layer L1 has compressive strain, and GaAs y Sb1-y When layer L2 has tensile strain, the energy at the upper end of the valence band corresponding to the wave vector shifted from the Γ point increases in the energy band diagram (see Figures 5 to 7). As a result, the band gap energy decreases in the wave vector shifted from the Γ point, making optical transitions (electron-hole recombination) more likely to occur in that wave vector. Since such optical transitions occur at wavelengths close to the absorption edge wavelength, it is thought that the quantum efficiency is higher at that wavelength.

[0045] Also, Ga x In 1-x As layer L1 has compressive strain, GaAs y S 1-y When layer L2 has tensile strain, the distance between the upper end of the valence band and the lower energy levels becomes smaller (see Figures 5 to 7). This is also considered to be one of the reasons why high quantum efficiency can be obtained in the semiconductor photodetector 100.

[0046] The following describes various experiments conducted to evaluate the semiconductor photodetector 100. The experiments described below are not intended to limit the present invention.

[0047] (Experiment 1) The semiconductor photodetector in the first experiment comprises a light-absorbing layer provided on an InP substrate. The thickness of the light-absorbing layer is 2.5 μm. The light-absorbing layer has a type II superlattice structure. The superlattice structure is Ga x In 1-x As layer and GaAs y S 1-y Includes layers. Ga x In 1-x As layer and GaAs y S 1-y The layers are stacked alternately in the stacking direction (corresponding to the first direction D1 in Figures 1 and 2). x In 1-x As layer and GaAs y S 1-y The thickness of each layer is 6.3 nm. The Ga composition x is 0.426. Therefore, Ga x In 1-xThe As layer has compressive strain. The As composition y is 0.551. Therefore, GaAs y S 1-y The layer has tensile strain. x In 1-x The AS layer has 21 Ga x In 1-x Contains a monolayer of As. GaAs y S 1-y The layer consists of 21 GaAs y S 1-y It contains a monolayer.

[0048] (Experiment 2) The semiconductor photodetector in the second experiment has the same configuration as the semiconductor photodetector in the first experiment, except for the following: In the second experiment, the Ga composition x is 0.468. The As composition y is 0.512. Therefore, Ga x In 1-x As layer and GaAs y S 1-y Each layer is free from distortion. x In 1-x The AS layer has 20 Ga x In 1-x Contains a monolayer of As. GaAs y S 1-y The layer consists of 20 GaAs y S 1-y It contains a monolayer. Therefore, Ga x In 1-x As layer and GaAs y S 1-y Each layer has a thickness of 6.0 nm.

[0049] (Experiment 3) The semiconductor photodetector in the third experiment has the same configuration as the semiconductor photodetector in the second experiment, except that the Ga composition x is 0.510 and the As composition y is 0.472. x In 1-x The As layer has tensile strain. GaAs y S 1-y The layer has compressive strain. Ga x In 1-x As layer and GaAs y S1-y Each layer has a thickness of 6.0 nm.

[0050] (Quantum efficiency) The quantum efficiency of the semiconductor photodetectors used in Experiments 1 through 3 was calculated with respect to the wavelength of light through simulation. The temperature used in the simulation was 250 Kelvin (K). The simulation results are shown in Figure 4.

[0051] Figure 4 is a graph showing examples of the relationship between the quantum efficiency and wavelength of semiconductor photodetectors in the first to third experiments. In the graph in Figure 4, the horizontal axis represents the wavelength (μm) of light absorbed by the light-absorbing layer. The vertical axis represents the quantum efficiency of the semiconductor photodetector. Spectrum SP1 shows the quantum efficiency in the first experiment. Spectrum SP2 shows the quantum efficiency in the second experiment. Spectrum SP3 shows the quantum efficiency in the third experiment. As shown in Figure 4, the absorption edge wavelength was approximately 2.7 μm in all three experiments. In the first wavelength range close to the absorption edge wavelength (e.g., 2.3 to 2.5 μm) and the second wavelength range further from the absorption edge wavelength (e.g., 1.8 to 1.9 μm), the first experiment showed a higher quantum efficiency than the second and third experiments. In the first wavelength range close to the absorption edge wavelength, the quantum efficiency in the first experiment was greater than 0.1, while the quantum efficiency in the second and third experiments was less than 0.1.

[0052] (Energy band diagram) Energy band diagrams were created for the semiconductor photodetectors used in Experiments 1 through 3 through simulation. The temperature used in the simulation was 250 Kelvin (K). The simulation results are shown in Figures 5 to 7.

[0053] Figure 5 is a graph showing an example of the energy band diagram for a semiconductor photodetector from the first experiment. Figure 6 is a graph showing an example of the energy band diagram for a semiconductor photodetector from the second experiment. Figure 7 is a graph showing an example of the energy band diagram for a semiconductor photodetector from the third experiment. In the graphs from Figures 5 to 7, the horizontal axis represents the value obtained by multiplying the absolute value of the wave vector k by (2π / a1). a1 is the lattice constant of the InP substrate. [-110] and

[0110] on the horizontal axis represent the direction of the wave vector k. Ga x In 1-x As layer and GaAs y S 1-y The layer stacking direction is the z-direction. In each graph, Ec represents the energy at the bottom of the conduction band, and Ev represents the energy at the top of the valence band. The energy at the top of the valence band has two values ​​due to the two spin orbitals. The lower energy levels, which have lower energies than the top of the valence band, also have two values.

[0054] As shown in Figure 5, in the first experiment, the band gap energy Eg was 0.479 eV, meaning the band gap wavelength λg was 2.59 μm. As shown in Figure 6, in the second experiment, the band gap energy Eg was 0.479 eV, meaning the band gap wavelength λg was 2.59 μm. As shown in Figure 7, in the third experiment, the band gap energy Eg was 0.474 eV, meaning the band gap wavelength λg was 2.62 μm.

[0055] As shown in Figures 5 to 7, the energy band diagram in the first experiment differed from that in the second and third experiments. One reason for the high quantum efficiency obtained in the first experiment is thought to be the difference in the energy band diagram.

[0056] In the first experiment, the energy at the upper end of the valence band corresponding to wave vectors shifted from the Γ point was larger compared to the second and third experiments. That is, in the first experiment, the upper end of the valence band was located near the straight line with energy 0 eV, compared to the second and third experiments. As a result, in the first experiment, the band gap energy is small for wave vectors shifted from the Γ point. Therefore, optical transitions (electron-hole recombination) are more likely to occur at these wave vectors. Since such optical transitions occur at wavelengths close to the absorption edge wavelength, it is thought that the quantum efficiency is higher at these wavelengths.

[0057] Furthermore, in the first experiment, the distance between the upper end of the valence band and the lower energy levels was closer compared to the second and third experiments. This is also considered to be one of the reasons why high quantum efficiency was obtained in the first experiment.

[0058] (Experiment 4) The semiconductor photodetector in Experiment 4 has the same configuration as the semiconductor photodetector in Experiment 1, except for the following point. In Experiment 4, the Ga composition x is 0.221. Therefore, Ga x In 1-x The As layer has compressive strain. The As composition y is 0.733. Therefore, GaAs y S 1-y The layer has tensile strain. x In 1-x The AS layer has 13 Ga x In 1-x Contains a monolayer of As. GaAs y S 1-y The layer consists of 15 GaAs y S 1-y It contains a monolayer. That is, the superlattice structure in the fourth experiment is (Ga 0.221 In 0.779 As) 13 (GaAs 0.733 S 0.267 ) 15 It has the structure represented by [formula]. In the fourth experiment, the band gap energy Eg was 0.472 eV. That is, the band gap wavelength λg was 2.628 μm.

[0059] (Quantum efficiency) For the semiconductor photodetector used in Experiment 4, the quantum efficiency with respect to the wavelength of light was calculated by simulation. The temperature used in the simulation was 250 Kelvin (K). The simulation results are shown in Figure 8.

[0060] Figure 8 is a graph showing an example of the relationship between the quantum efficiency of the semiconductor photodetector and wavelength in Experiment 4. The vertical and horizontal axes of the graph in Figure 8 are the same as those of the graph in Figure 4, respectively. As shown in Figure 8, in Experiment 4, high quantum efficiencies greater than 0.1 were obtained in the first wavelength range close to the absorption edge wavelength (e.g., 2.3 to 2.5 μm) and the second wavelength range far from the absorption edge wavelength (e.g., 1.8 to 1.9 μm).

[0061] Although exemplary embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments.

[0062] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not in the sense described above, and all modifications within the sense and scope equivalent to the claims are intended. [Explanation of Symbols]

[0063] 10…InP board 12…Group III-V compound semiconductor layer 14…Second III-V compound semiconductor layer 16…Light-absorbing layer 20…III-V compound semiconductor layer 22…III-V compound semiconductor layer 30...Electrode 40...electrode 100... Semiconductor photodetector AR…Area D1…first direction L…Incoming light L1…Ga x In 1-x As layer L2…GaAs y S 1-y layer SP1…Spectrum SP2...spectrum SP3...spectrum

Claims

1. Indium phosphide substrate, A first-type conductivity first-group III-V compound semiconductor layer, A second-conductivity type 2III-V compound semiconductor layer, A light-absorbing layer is provided between the first III-V compound semiconductor layer and the second III-V compound semiconductor layer, Equipped with, The first III-V compound semiconductor layer is provided between the indium phosphide substrate and the light absorption layer. The light-absorbing layer has a Type II superlattice structure, The superlattice structure includes a gallium indium arsenide layer and a gallium arsenide antimony layer. The gallium indium arsenide layer has compressive strain, The gallium arsenide antimony layer has tensile strain, A semiconductor photodetector having an absorption edge wavelength of 2.5 to 4 μm.

2. The semiconductor photodetector according to claim 1, wherein the gallium composition x of the gallium indium arsenide layer is 0.17 or more.

3. The semiconductor photodetector according to claim 1 or claim 2, wherein the arsenic composition y of the gallium arsenide antimony layer is 0.78 or less.

4. The semiconductor photodetector according to claim 1 or claim 2, wherein the gallium composition x of the gallium indium arsenide layer is 0.46 or less.

5. The semiconductor photodetector according to claim 1 or claim 2, wherein the arsenic composition y of the gallium arsenide antimony layer is 0.52 or greater.

6. The gallium indium arsenide layer comprises n gallium indium arsenide monolayers, The gallium arsenide antimony layer comprises m gallium arsenide antimony monolayers, The semiconductor photodetector according to claim 1 or claim 2, wherein n and m are integers between 13 and 25.

7. When the gallium composition of the gallium indium arsenide layer is x and the arsenic composition of the gallium arsenide antimony layer is y, y≦1.054x ２ -2.809x+1.594 A semiconductor photodetector according to claim 1 or claim 2, satisfying the requirements.

8. When the gallium composition of the gallium indium arsenide layer is x and the arsenic composition of the gallium arsenide antimony layer is y, y≧0.137x ２ -0.627x+0.775 A semiconductor photodetector according to claim 1 or claim 2, satisfying the requirements.

9. The semiconductor photodetector according to claim 1 or claim 2, wherein the number of pairs of the gallium indium arsenide layer and the gallium arsenide antimony layer is 200 to 400.

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