JP2011071306A - Photodetector, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an photodetector having high sensitivity, and to provide a method of manufacturing the same. <P>SOLUTION: The photodetector includes a lower electrode 1, an active layer 9 formed on the lower electrode 1, and an upper electrode 4 formed on the active layer 9. The active layer 9 includes barrier layers 2 and quantum well layers 3 lattice-matching the barrier layers 2. The barrier layers 2 and the quantum well layers 3 constitute a type II superlattice. The quantum well layer 3 includes first compound semiconductor layers 3a and 3c, and a second compound semiconductor layer 3b causing crystals of the first compound semiconductor layers 3a and 3c to generate lattice strain. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a photodetector and a manufacturing method thereof.

  In recent years, research has been conducted to apply an InAs / GaSb type II superlattice to an infrared detector.

  However, when the material of the quantum well layer is InAs and the material of the barrier layer is GaSb, it is difficult to achieve both adjustment of the detectable wavelength and improvement of sensitivity. For example, in the infrared detector, the wavelength range of 8 μm to 12 μm, which has a large atmospheric transmittance, is widely used. The thickness of the quantum well layer and the barrier layer is adjusted so that infrared rays in this wavelength range can be detected. Then, the excitation transition probability, that is, the absorption coefficient is lowered, and sufficient sensitivity cannot be obtained. Conversely, if the thicknesses of the quantum well layer and the barrier layer are adjusted so that the absorption coefficient becomes high, infrared rays in the 8 μm to 12 μm band cannot be detected.

  Therefore, conventionally, a technique has been proposed in which a mixed crystal (GaInSb) in which InSb is added to GaSb is used as a material for the barrier layer to modulate the band structure. In addition, a technique has been proposed in which the GaSb layer is thinned and the miniband width is widened up and down by coupling of wave functions of the conduction band in the InAs layer to lower the transition energy between the conduction band and the valence band. .

  However, when GaInSb is used, In clusters are generated in the barrier layer, and the flow of photocurrent is hindered. For this reason, it becomes difficult to detect the photocurrent and it is difficult to obtain high sensitivity. Further, when the GaSb layer is thinned, the sensitivity is only slightly improved and it is difficult to obtain sufficient sensitivity.

Japanese Patent Laid-Open No. 5-160429 JP-A-6-196745

Mat. Res. Soc. Symp. Proc. Vol. 607, 77 (2000) D.L. Smith et al., J. of Appl. Phys. Vol. 62, 2545 (1987) Y. Wei et al., Appl. Phys. Lett. Vol. 80, 3262 (2002) G.J.Brown, Proc. Of SPIE Vol. 5783, 65 (2005)

  An object of the present invention is to provide a photodetector and a method for manufacturing the same, which can obtain high sensitivity.

  One aspect of the photodetector includes a lower electrode, an active layer formed above the lower electrode, and an upper electrode formed above the active layer. The active layer is provided with a barrier layer and a quantum well layer lattice-matched with the barrier layer. The barrier layer and the quantum well layer constitute a type II superlattice. At least one of the barrier layer and the quantum well layer is provided with a first compound semiconductor layer and a second compound semiconductor layer that causes lattice distortion in the crystal of the first compound semiconductor layer. . Note that the lattice constant of the crystal constituting the barrier layer and the lattice constant of the crystal constituting the quantum well layer do not need to be completely matched, and for example, there is a difference between these lattice constants to such an extent that epitaxial growth is possible. There may be.

  According to the above photodetector, the band structure changes due to the influence of lattice distortion, and high sensitivity can be obtained.

It is a figure which shows the relationship between the lattice constant (temperature: 0K) and the bandwidth at a Γ point in various III-V group compound semiconductors. It is sectional drawing which shows the structure of the photodetector which concerns on 1st Embodiment. FIG. 4 is a diagram showing a relationship between the thickness of a strain generation layer 3b that uses the Vegard law and the average lattice constant of crystals constituting the quantum well layer 3; It is sectional drawing which shows the structure of the photodetector which concerns on 2nd Embodiment. It is sectional drawing which shows the structure of the photodetector which concerns on 3rd Embodiment. It is sectional drawing which shows the structure of the photodetector which concerns on 4th Embodiment. It is sectional drawing which shows the manufacturing method of the photodetector which concerns on 4th Embodiment in process order. It is sectional drawing which shows the manufacturing method of a photodetector in order of a process following FIG. 7A.

(Background to the embodiment)
The inventor of the present application has studied in detail a technique using conventional GaInSb as a material for the barrier layer, and as a result, adjustment of the detectable band (cutoff wavelength) can be performed even if there is no bandwidth modulation accompanying the use of GaInSb. We found that this is possible by controlling the lattice strain of the layer.

  Here, FIG. 1 shows the relationship between the lattice constant (temperature: 0 K) and the bandwidth at the Γ point in various III-V compound semiconductors. The source of the physical property constants shown in FIG. 1 is “I. Vurgaftman et al., J. of Appl. Phys. Vol. 89, 5815 (2001)”. As can be seen from FIG. 1, when InSb is added to GaSb, the resulting mixed crystal (GaInSb) has a lattice constant of about 6.10 Å (GaSb lattice constant) depending on the ratio of GaSb and InSb. It greatly changes up to 6.48Å (the lattice constant of InSb). On the other hand, the lattice constant of InAs is about 6.06Å. Therefore, when the GaInSb barrier layer and the InAs quantum well layer are epitaxially combined, lattice strain in the direction of increasing the lattice constant is generated in the InAs quantum well layer, and the lattice constant is set in the GaInSb barrier layer. Lattice distortion in the direction of decreasing occurs. These lattice strains increase as the In ratio in the GaInSb barrier layer increases.

  In the technique using conventional GaInSb as the material of the barrier layer, the cutoff wavelength can be adjusted with the occurrence of such lattice strain. As described above, it has been found that the cutoff wavelength can be adjusted by generating an appropriate lattice strain in the quantum well layer without using a mixed crystal in which In clusters are generated.

  Hereinafter, embodiments will be specifically described with reference to the accompanying drawings.

(First embodiment)
First, the first embodiment will be described. FIG. 2 is a cross-sectional view showing the structure of the photodetector according to the first embodiment.

  In the first embodiment, a plurality of stacked structures of the barrier layer 2 and the quantum well layer 3 positioned thereon are formed on the lower electrode 1. A barrier layer 2 is formed on the uppermost quantum well layer 3, and an upper electrode 4 is formed on the barrier layer 2. The barrier layer 2 and the quantum well layer 3 are lattice-matched to each other. The barrier layer 2 and the quantum well layer 3 constitute a type II superlattice. Such a barrier layer 2 and quantum well layer 3 are included in the active layer 9.

The lower electrode 1 is, for example, a GaSb layer doped with a thickness of 1000 nm and Te of 8 × 10 ¹⁷ cm ⁻³ . The barrier layer 2 is, for example, a GaSb layer having a thickness of 2.5 nm. The upper electrode 4 is, for example, a GaSb layer having a thickness of 300 nm and Be doped at a concentration of 7 × 10 ¹⁷ cm ⁻³ .

  The quantum well layer 3 includes a base layer (first compound semiconductor layer) 3a, a strain generation layer (second compound semiconductor layer) 3b located thereon, and a base layer (first compound semiconductor layer) located thereon. Semiconductor layer) 3c is included. The total thickness of the quantum well layer 3 is 2.5 nm. The base layers 3a and 3c are, for example, InAs layers, and the strain generation layer 3b is, for example, an InSb layer. The base layer 3a, the strain generation layer 3b, and the base layer 3c are lattice-matched with each other. Then, the base layers 3a and 3c act as quantum wells with respect to the barrier layer 2, and the strain generation layer 3b causes lattice strain in the crystals of the base layers 3a and 3c.

  In the first embodiment configured as described above, the lattice constant of InAs constituting the base layers 3a and 3c of the quantum well layer 3 is the same as the lattice constant of GaSb constituting the barrier layer 2 and the InSb constituting the strain generation layer 3b. Is smaller than the lattice constant. For this reason, a large lattice strain is generated in the InAs constituting the base layers 3a and 3c in the direction in which the lattice constant increases.

  The magnitude of the lattice strain changes depending on the ratio between the total thickness of the base layers 3a and 3c and the thickness of the strain generation layer 3b, for example. FIG. 3 is a diagram showing the relationship between the thickness of the strain generating layer 3b using the Vegard law and the average lattice constant of the crystals constituting the quantum well layer 3. As shown in FIG. As shown in FIG. 3, when the thickness of the strain generation layer 3b is 0 nm, that is, when the entire quantum well layer 3 is made of InAs, the average lattice constant is about 6.06Å. Further, when the thickness of the strain generation layer 3b is 2.5 nm, that is, when the entire quantum well layer 3 is made of InSb, the average lattice constant is about 6.48 mm. Therefore, when the Vegard law is used, when the thickness of the strain generation layer 3b is 1.1 nm, the average lattice constant of the quantum well layer 3 is about 6.25 mm.

On the other hand, regarding the technology using conventional GaInSb as the material of the barrier layer, when the thickness of the Ga _0.6 In _0.4 Sb barrier layer is 2.5 nm and the thickness of the InAs quantum well layer is 2.5 nm, the cutoff wavelength is There is a report of 10.7 μm. And the lattice constant of Ga _0.6 In _0.4 Sb is about 6.25Å with the help of Vegard's law.

  Therefore, also in this embodiment, when the thickness of the strain generation layer 3b is 1.1 nm, it can be said that a cutoff wavelength of about 10.7 μm can be obtained. Moreover, if the thickness of the strain generation layer 3b is adjusted, it is possible to absorb infrared rays in the 8 μm to 12 μm band. Furthermore, since it is not necessary to adjust the thickness of the barrier layer 2 and the quantum well layer 3 to such an extent that the sensitivity is lowered, it is possible to obtain high sensitivity.

(Second Embodiment)
Next, a second embodiment will be described. FIG. 4 is a cross-sectional view showing the structure of the photodetector according to the second embodiment.

  In the second embodiment, as in the first embodiment, a plurality of stacked structures of the barrier layer 2 and the quantum well layer 3 positioned thereon are formed on the lower electrode 1. A barrier layer 2 is formed on the uppermost quantum well layer 3, and an upper electrode 4 is formed on the barrier layer 2. The barrier layer 2 and the quantum well layer 3 are lattice-matched to each other. The barrier layer 2 and the quantum well layer 3 constitute a type II superlattice. Such a barrier layer 2 and quantum well layer 3 are included in the active layer 9. However, the configurations of the barrier layer 2 and the quantum well layer 3 are different from those of the first embodiment.

  That is, the barrier layer 2 includes a base layer (first compound semiconductor layer) 2a, a strain generation layer (12th compound semiconductor layer) 2b located thereon, and a base layer (first compound semiconductor layer) located thereon. Layer) 2c. The total thickness of the barrier layer 2 is 2.5 nm. The base layers 2a and 2c are, for example, GaSb layers, and the strain generation layer 2b is, for example, an InSb layer. The base layer 2a, the strain generation layer 2b, and the base layer 2c are lattice-matched with each other. The quantum well layer 3 is, for example, an InAs layer having a thickness of 2.5 nm. The base layers 2a and 2c act as a barrier against the quantum well layer 3, and the strain generation layer 2b causes lattice strain in the crystals of the base layers 2a and 2c.

  In the second embodiment configured as described above, the lattice constant of InSb constituting the strain generation layer 2b of the barrier layer 2 is larger than the lattice constant of GaSb constituting the base layers 2a and 2c. For this reason, the average lattice constant of the crystals constituting the barrier layer 2 is larger than the lattice constant of GaSb itself. On the other hand, the quantum well layer 3 is lattice-matched with the barrier layer 2. Therefore, a larger lattice strain is generated in InAs constituting the quantum well layer 3 than in the case where the barrier layer 2 is made only of GaSb.

  The magnitude of the lattice strain changes depending on the ratio between the total thickness of the base layers 2a and 2c and the thickness of the strain generation layer 2b, for example. When the thickness of the strain generation layer 2b is 0 nm, that is, when the entire barrier layer 2 is made of GaSb, the average lattice constant is about 6.10 mm. Further, when the thickness of the strain generation layer 2b is 2.5 nm, that is, when the entire barrier layer 2 is made of InSb, the average lattice constant is about 6.48 mm. Therefore, when the Vegard law is used, when the thickness of the strain generation layer 2b is 1.0 nm, the average lattice constant of the barrier layer 2 is about 6.25 mm.

On the other hand, as described above, regarding the technology using conventional GaInSb as the material of the barrier layer, the thickness of the Ga _0.6 In _0.4 Sb barrier layer is 2.5 nm and the thickness of the InAs quantum well layer is 2.5 nm. In addition, there is a report that the cutoff wavelength is 10.7 μm. And the lattice constant of Ga _0.6 In _0.4 Sb is about 6.25Å with the help of Vegard's law.

  Therefore, in this embodiment, when the thickness of the strain generation layer 2b is 1.0 nm, a cutoff wavelength closer to 10.7 μm is obtained than in the case where the strain generation layer 3b is 1.1 nm in the first embodiment. It can be said that. This is because the configuration of the quantum well layer and the barrier layer in the first embodiment is different from that of the conventional technique, whereas the configuration of the quantum well layer is common in the second embodiment. It is. Similarly to the first embodiment, by adjusting the thickness of the strain generating layer 2b, it is possible to absorb infrared rays in the 8 μm to 12 μm band. Furthermore, since it is not necessary to adjust the thickness of the barrier layer 2 and the quantum well layer 3 to such an extent that the sensitivity is lowered, it is possible to obtain high sensitivity.

(Third embodiment)
Next, a third embodiment will be described. FIG. 5 is a cross-sectional view showing the structure of the photodetector according to the third embodiment.

  In the third embodiment, as in the first embodiment, a plurality of stacked structures of the barrier layer 2 and the quantum well layer 3 positioned thereon are formed on the lower electrode 1. A barrier layer 2 is formed on the uppermost quantum well layer 3, and an upper electrode 4 is formed on the barrier layer 2. The barrier layer 2 and the quantum well layer 3 are lattice-matched to each other. The barrier layer 2 and the quantum well layer 3 constitute a type II superlattice. Such a barrier layer 2 and quantum well layer 3 are included in the active layer 9. However, the configuration of the barrier layer 2 is different from that of the first embodiment.

  That is, the barrier layer 2 includes a base layer 2a, a strain generation layer 2b located thereon, and a base layer 2c located thereon. The total thickness of the barrier layer 2 is 2.5 nm. The base layers 2a and 2c are, for example, GaSb layers, and the strain generation layer 2b is, for example, an InSb layer. The base layer 2a, the strain generation layer 2b, and the base layer 2c are lattice-matched with each other.

  As described above, the third embodiment has a configuration in which the first embodiment and the second embodiment are combined. Therefore, the third embodiment can provide the same effects as those of the first and second embodiments. Further, since the strain generation layer 2b and the strain generation layer 3b are included, the cutoff wavelength can be adjusted over a wider range.

(Fourth embodiment)
Next, a fourth embodiment will be described. FIG. 6 is a cross-sectional view showing the structure of the photodetector according to the fourth embodiment. Although the light detector (infrared detector) according to the twenty-fourth embodiment is provided with a plurality of pixels, FIG. 6 shows only one pixel.

In the fourth embodiment, a lower electrode 11 is formed on a substrate 10 such as a GaSb substrate. The lower electrode 11 is a GaSb layer into which impurities are introduced, for example, and the thickness of the lower electrode 11 is about 1000 nm. For example, the impurity in the lower electrode 11 is Te, and its concentration is about 8 × 10 ¹⁷ cm ⁻³ .

  On the lower electrode 11, a plurality of (for example, ten) stacked structures of the barrier layer 12 and the quantum well layer 13 positioned thereon are formed. The barrier layer 2 and the quantum well layer 3 are lattice-matched to each other. The barrier layer 12 and the quantum well layer 13 constitute a type II superlattice. Such a barrier layer 12 and quantum well layer 13 are included in the active layer 19. The barrier layer 12 is, for example, a GaSb layer having a thickness of 2.5 nm. The quantum well layer 13 includes a base layer (first compound semiconductor layer) 13a, a strain generation layer (second compound semiconductor layer) 13b located thereon, and a base layer (first compound semiconductor layer) located thereon. ) 13c is included. The total thickness of the quantum well layer 13 is 2.5 nm. The base layers 13a and 13c are, for example, InAs layers, and the strain generation layer 13b is, for example, an InSb layer. The base layer 13a, the strain generation layer 13b, and the base layer 13c are lattice-matched with each other. The base layers 13a and 13c act as quantum wells with respect to the barrier layer 12, and the strain generation layer 13b causes lattice strain in the crystals of the base layers 13a and 13c.

A barrier layer 12 is formed on the uppermost quantum well layer 13, and an upper electrode 14 is formed on the barrier layer 12. The upper electrode 14 is a GaSb layer into which impurities are introduced, for example, and the thickness of the upper electrode 14 is about 300 nm. For example, the impurity in the upper electrode 14 is Be, and its concentration is about 7 × 10 ¹⁷ cm ⁻³ .

  In the present embodiment, isolation grooves 17 that isolate pixels from each other are formed in the barrier layer 12, the quantum well layer 13, and the upper electrode 14. A terminal 16 is formed in a portion exposed from the separation groove 17 of the lower electrode 11. A terminal 15 is formed on the upper electrode 14.

  According to the fourth embodiment configured as described above, the same effect as that of the first embodiment can be obtained. That is, it is possible to detect infrared rays in a predetermined band while obtaining high sensitivity.

  Next, the manufacturing method of the photodetector which concerns on 4th Embodiment is demonstrated. 7A and 7B are cross-sectional views showing a method of manufacturing a photodetector according to the fourth embodiment in the order of steps.

  First, as shown in FIG. 7A (a), a lower electrode 11 is formed on a substrate 10 by a molecular beam epitaxy (MBE) method. The substrate temperature at this time is about 530 ° C., for example.

  Next, as shown in FIG. 7A (b), the barrier layer 12 is formed on the lower electrode 11 by the MBE method. The substrate temperature at this time is 390 ° C., for example.

  Thereafter, as shown in FIG. 7A (c), a base layer 13a, a strain generation layer 13b, and a base layer 13c are formed on the barrier layer 12 by the MBE method. That is, the quantum well layer 13 is formed on the barrier layer 12. The substrate temperature at this time is 390 ° C., for example.

  Subsequently, as shown in FIG. 7B (d), the barrier layer 12 is formed on the quantum well layer 13. The formation of the barrier layer 12 and the formation of the quantum well layer 13 are repeated so that 10 sets of the barrier layer 12 and the quantum well layer 13 are positioned on the lower electrode 11. Further, the barrier layer 12 is formed on the uppermost quantum well layer 13. As a result, an active layer 19 including 11 barrier layers 12 and 10 quantum well layers 13 exists above the lower electrode 11.

  Next, as shown in FIG. 7B (e), the upper electrode 14 is formed on the uppermost barrier layer 12 by the MBE method. The substrate temperature at this time is 390 ° C., for example.

  Thereafter, isolation grooves 17 are formed in the barrier layer 12, the quantum well layer 13, and the upper electrode 14 by lithography and etching techniques. That is, pixel separation is performed. Furthermore, the terminal 15 is formed on the upper electrode 14, and the terminal 16 is formed on the part exposed from the separation groove 17 of the lower electrode 11 (see FIG. 6).

  In this way, the photodetector can be manufactured.

  In the fourth embodiment, the same function as that of the first embodiment is adopted for the portion functioning as the active layer, but this portion is the same as that of the second embodiment or the third embodiment. A configuration may be employed.

  Each layer may be formed by a method other than the MBE method. For example, a metal organic chemical vapor deposition (MOCVD) method or the like may be employed.

  In any embodiment, the type and concentration of impurities added to the upper electrode or the lower electrode are not particularly limited.

  Moreover, the material of the barrier layer and the quantum well layer is not particularly limited. Examples of the combination of the barrier layer / quantum well layer include GaSb / InAs, GaSb / InGaAs, GaSbAs / InAs, GaSbAs / InGaAs, GaAlSb / InAs, GaAlSb / InGaAs, AlSb / InAs, AlSb / InGaAs, and AlSbAs / InAs. AlSbAs / InGaAs and the like.

  Moreover, the material of the strain generation layer is not particularly limited. For example, a compound semiconductor such as GaAs, AlAs, InP, and AlSb in FIG. 1 may be used. Moreover, you may use these mixed crystals. However, since a mixed crystal containing In may generate In clusters, it is preferable that the strain generation layer containing the mixed crystal containing In is thin.

  Further, the thickness of the strain generation layer can be determined by various methods. For example, as described above, the thickness of the strain generation layer may be determined with reference to a cutoff wavelength obtained when a GaInSb barrier layer and an InAs quantum well layer are used. Further, a relationship between the thickness of the strain generation layer and the cutoff wavelength may be obtained, and the thickness of the strain generation layer may be determined according to the cutoff wavelength from this relationship.

  The position of the strain generation layer in the quantum well layer and the position of the strain generation layer in the barrier layer are not particularly limited. The strain generating layer may be located at the center in the thickness direction of the quantum well layer or the barrier layer, and may be located below or above it. In addition, strain generation layers may be provided at a plurality of locations in the thickness direction of the quantum well layer or the barrier layer.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1)
A lower electrode;
An active layer formed above the lower electrode;
An upper electrode formed above the active layer;
Have
The active layer is
A barrier layer;
A quantum well layer lattice matched to the barrier layer;
Have
The barrier layer and the quantum well layer constitute a type II superlattice,
At least one of the barrier layer and the quantum well layer is
A first compound semiconductor layer;
A second compound semiconductor layer that causes lattice distortion in a crystal of the first compound semiconductor layer;
An optical detector comprising:

(Appendix 2)
The photodetector according to claim 1, wherein the active layer has a plurality of stacked structures in which the barrier layers and the quantum well layers are alternately stacked.

(Appendix 3)
The barrier layer is a GaSb layer;
3. The photodetector according to appendix 1 or 2, wherein the first compound semiconductor layer is an InAs layer.

(Appendix 4)
The quantum well layer is an InAs layer;
3. The photodetector according to appendix 1 or 2, wherein the first compound semiconductor layer is a GaSb layer.

(Appendix 5)
The photodetector according to appendix 3 or 4, wherein the second compound semiconductor layer is an InSb layer.

(Appendix 6)
Two or more first compound semiconductor layers are provided,
6. The photodetector according to any one of appendices 1 to 5, wherein the second compound semiconductor layer is sandwiched between the first compound semiconductor layers.

(Appendix 7)
Forming an active layer above the lower electrode;
Forming an upper electrode above the active layer;
Have
The step of forming the active layer includes:
Forming a barrier layer;
Forming a quantum well layer lattice matched to the barrier layer;
Have
The barrier layer and the quantum well layer constitute a type II superlattice,
At least one of the barrier layer and the quantum well layer is
A first compound semiconductor layer;
A second compound semiconductor layer that causes lattice distortion in a crystal of the first compound semiconductor layer;
The manufacturing method of the photodetector characterized by having.

(Appendix 8)
8. The method of manufacturing a photodetector according to appendix 7, wherein the active layer has a plurality of stacked structures in which the barrier layers and the quantum well layers are alternately stacked.

(Appendix 9)
The barrier layer is a GaSb layer;
9. The method of manufacturing a photodetector according to appendix 7 or 8, wherein the first compound semiconductor layer is an InAs layer.

(Appendix 10)
The quantum well layer is an InAs layer;
9. The method of manufacturing a photodetector according to appendix 7 or 8, wherein the first compound semiconductor layer is a GaSb layer.

1: Lower electrode 2: Barrier layer 2a, 2c: Base layer 2b: Strain generation layer 3: Quantum well layer 3a, 3c: Base layer 3b: Strain generation layer 4: Upper electrode 9: Active layer 10: Substrate 11: Lower electrode 12: Barrier layer 13: Quantum well layer 13a, 13c: Base layer 13b: Strain generation layer 14: Upper electrode 19: Active layer

Claims (6)

A lower electrode;
An active layer formed above the lower electrode;
An upper electrode formed above the active layer;
Have
The active layer is
A barrier layer;
A quantum well layer lattice matched to the barrier layer;
Have
The barrier layer and the quantum well layer constitute a type II superlattice,
At least one of the barrier layer and the quantum well layer is
A first compound semiconductor layer;
A second compound semiconductor layer that causes lattice distortion in a crystal of the first compound semiconductor layer;
An optical detector comprising:   The photodetector according to claim 1, wherein the active layer has a plurality of stacked structures in which the barrier layers and the quantum well layers are alternately stacked. The barrier layer is a GaSb layer;
The photodetector according to claim 1, wherein the first compound semiconductor layer is an InAs layer. The quantum well layer is an InAs layer;
The photodetector according to claim 1, wherein the first compound semiconductor layer is a GaSb layer.   The photodetector according to claim 3, wherein the second compound semiconductor layer is an InSb layer. Forming an active layer above the lower electrode;
Forming an upper electrode above the active layer;
Have
The step of forming the active layer includes:
Forming a barrier layer;
Forming a quantum well layer lattice matched to the barrier layer;
Have
The barrier layer and the quantum well layer constitute a type II superlattice,
At least one of the barrier layer and the quantum well layer is
A first compound semiconductor layer;
A second compound semiconductor layer that causes lattice distortion in a crystal of the first compound semiconductor layer;
The manufacturing method of the photodetector characterized by having.

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