JPWO2019215903A1 - Photodetector - Google Patents

Abstract

In order to suppress the generation of dark current, a substrate, a light receiving layer formed above the substrate, and an electron barrier layer formed in contact with the light receiving layer and containing a plurality of quantum dots are provided, and the base of the electron barrier layer. The semiconductor of the material and the semiconductor constituting the quantum dot are photodetectors having different lattice constants.

Description

The present invention relates to a photodetector that detects infrared rays.

Bulk semiconductors such as mercury cadmium tellurium (HgCdTe) and compound semiconductors are used as the light receiving material of the photodetector element for detecting infrared rays. In a photodetector element using a compound semiconductor as a light receiving material, an electron barrier layer is interposed between the light receiving layer and the contact layer in order to reduce the current (hereinafter referred to as dark current) that flows regardless of the presence or absence of infrared light reception. The structure to be used is disclosed.

In Non-Patent Document 1, an aluminum gallium antimonide (AlGaSb) layer is electron with respect to a light receiving layer having a type 2 superlattice structure in which indium arsenide (InAs) and gallium antimonide (GaSb) are alternately laminated. A photodetector included as a barrier layer is disclosed.

Non-Patent Document 2 discloses a structure in which an aluminum / arsenic / antimony (AlAsSb) barrier layer is provided on the InAs bulk light receiving layer.

Non-Patent Document 3 discloses a structure in which an AlGaSb barrier layer is provided on an indium gallium arsenide / antimony (InGaAsSb) bulk light receiving layer.

Non-Patent Document 4 describes a photodetector element that uses an electron barrier layer having a type 1 superlattice structure with respect to a light receiving layer having a type 2 superlattice structure in which InAs, aluminum antimonide (AlSb), and GaSb are alternately laminated. Is disclosed. The photodetector element of Non-Patent Document 4 includes an electron barrier layer having a type 1 superlattice structure in which AlAsSb and GaSb are alternately laminated.

Patent Document 1 describes an infrared detection unit having a plurality of laminated quantum dot layers, and at least one dark current reduction layer provided at an end of the infrared detection unit in the stacking direction and having a quantum well structure. The infrared detector having is disclosed.

Patent Document 2 discloses an infrared detector having a structure in which an intermediate layer in which quantum dots serving as a light absorbing portion are embedded and an intermediate layer in which quantum dots serving as a potential barrier are embedded are laminated.

JP-A-2007-184512 Japanese Unexamined Patent Publication No. 2006-186183

JB Rodriguez, E. Plis, G. Bishop, YD Sharma, H. Kim, LR Dawson, S. Krishna, “nBn structure based on InAs / GaSb type-II strained layer superlattices”, Applied Physics Letters, vol.91, 043514 , 2007 S. Maimon, and G. W. Wicks, “nBn detector, an infrared detector with reduced dark current and higher operating temperature,” Applied Physics Letters, vol.89, 151109, 2006 A. P. Craig et al., “Short-wave infrared barriode detectors using InGaAsSb absorption material lattice matched to GaSb,” Applied Physics Letters, vol.106, 201103, 2015 A Haddadi, R. Chevallier, A. Dehzangi, M. Razeghi, “Extended short-wavelength infrared nBn photodetectors based on type-II InAs / AlSb / GaSb superlattices with an AlAsSb / GaSb superlattice barrier”, Applied Physics Letters, vol.110 , 101104, 2017

According to the photodetector elements of Non-Patent Documents 1 to 4, the dark current can be reduced by introducing an electron barrier layer that serves as a potential wall for electrons between the contact layer and the light receiving layer. .. However, the photodetector elements of Non-Patent Documents 1 to 4 have a problem that the dark current cannot be suppressed enough to stably realize a high temperature operation exceeding 150 Kelvin.

An object of the present invention is to provide a photodetector element capable of solving the above-mentioned problems and suppressing the generation of dark current.

The photodetector element of one aspect of the present invention includes a substrate, a light receiving layer formed above the substrate, and an electron barrier layer formed in contact with the light receiving layer and containing a plurality of quantum dots. The semiconductor of the base material and the semiconductor constituting the quantum dot have different lattice constants.

According to the present invention, it becomes possible to provide a photodetector element capable of suppressing the generation of dark current.

It is a conceptual diagram which shows an example of the structure of the photodetector element which concerns on 1st Embodiment of this invention. It is a conceptual diagram which shows an example of the structure of the electron barrier layer included in the photodetector element which concerns on 1st Embodiment of this invention. It is a conceptual diagram which shows an example of the band structure of the electron barrier layer included in the photodetector element which concerns on 1st Embodiment of this invention. It is a flowchart for demonstrating the manufacturing method of the photodetector element which concerns on 1st Embodiment of this invention. It is a conceptual diagram which shows an example which forms the light receiving layer of the light detection element which concerns on 1st Embodiment of this invention in an array. It is a conceptual diagram for demonstrating an example of flip-chip joining a photodetector element and a readout circuit which concerns on 1st Embodiment of this invention. It is a conceptual diagram which shows an example of the structure of the photodetector element which concerns on 2nd Embodiment of this invention. It is a conceptual diagram which shows an example of the structure of the electron barrier layer included in the photodetector element which concerns on 2nd Embodiment of this invention. It is a conceptual diagram which shows an example of the band structure of the electron barrier layer included in the photodetector element which concerns on 2nd Embodiment of this invention. It is a flowchart for demonstrating the manufacturing method of the photodetector element which concerns on 2nd Embodiment of this invention. It is a conceptual diagram which shows an example of the structure of the photodetector element which concerns on 3rd Embodiment of this invention. It is a conceptual diagram which shows an example of the structure of the infrared ray detection apparatus which concerns on 4th Embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, although the embodiments described below have technically preferable limitations for carrying out the present invention, the scope of the invention is not limited to the following. In all the drawings used in the following embodiments, the same reference numerals are given to the same parts unless there is a specific reason. Further, in the following embodiments, repeated explanations may be omitted for similar configurations and operations. Further, the direction of the arrow in the drawing shows an example, and does not limit the direction of the signal between blocks.

(First Embodiment)
First, the photodetector element according to the first embodiment of the present invention will be described with reference to the drawings. The photodetector of the present embodiment includes an electron barrier layer having a structure in which quantum dots are embedded inside a bulk semiconductor.

FIG. 1 is a schematic view showing an example of the configuration of the photodetector element 10 of the present embodiment. As shown in FIG. 1, the photodetector 10 includes a substrate 11, a buffer layer 12, a first contact layer 13, an electron barrier layer 14, a light receiving layer 15, and a second contact layer 16. Note that FIG. 1 conceptually shows the configuration of the photodetector element 10, and does not accurately represent the scale of each configuration.

The substrate 11 is a substrate for forming an infrared detection structure. The substrate 11 is made of a compound semiconductor material. For example, the semiconductor composition of the substrate 11 is gallium antimonide (GaSb), indium phosphide (InP), gallium nitride (GaN), gallium arsenide (GaAs), or the like. The material of the substrate 11 is not limited to those listed here. The material constituting the substrate 11 may be selected according to the material used for the buffer layer 12, the first contact layer 13, the electron barrier layer 14, the light receiving layer 15, and the second contact layer 16. Further, the substrate 11 may be doped with impurities.

The buffer layer 12 is formed on the upper surface of the substrate 11. The buffer layer 12 is a layer in which crystals are grown according to the plane orientation of the upper surface of the substrate 11. The buffer layer 12 is preferably made of the same material as the substrate 11.

The first contact layer 13 is formed on the upper surface of the buffer layer 12. The first contact layer 13 contains a dopant. For example, when introducing an n-type dopant into the first contact layer 13, silicon (Si) can be used. For example, when a p-type dopant is used for the first contact layer 13, beryllium (Be) or zinc (Zn) can be used. The first contact layer 13 preferably has the same composition as the buffer layer 12. Further, the first contact layer 13 may have another semiconductor composition that is lattice-matched with the buffer layer 12. For example, when InP is used as the material of the substrate 11, InGaAs lattice-matched with InP can be used for the first contact layer 13.

The electron barrier layer 14 is laminated on the upper surface of the first contact layer 13. The electron barrier layer 14 has a structure in which a plurality of quantum dots having a narrower bandgap than the bulk semiconductor are included inside the bulk semiconductor as a base material. The base material of the electron barrier layer 14 and the semiconductor composition constituting the quantum dots have different lattice constants.

FIG. 2 is a conceptual diagram showing an example of the configuration of the electron barrier layer 14. As shown in FIG. 2, the electron barrier layer 14 has a structure in which a plurality of quantum dots 145 are included inside the bulk layer 141. The semiconductor composition of the quantum dots 145 has a narrower bandgap than the semiconductor composition of the bulk layer 141. The quantum dots 145 are naturally formed so that the distortion of the interface is eliminated when several molecular layers of a material having a semiconductor composition larger than that of the material of the bulk layer 141 are laminated in the middle of crystal growth of the bulk layer 141. It is a three-dimensional island-like structure. Quantum dots that are naturally formed in this way are called self-formed quantum dots.

For example, the electron barrier layer 14 contains quantum dots 145 having a semiconductor composition having a narrower bandgap than AlGaSb inside the aluminum gallium antimonide (AlGaSb) crystal-grown as the bulk layer 141. For example, examples of the semiconductor composition having a narrower bandgap than AlGaSb include indium antimonide (InSb), indium gallium antimonide (InGaSb), and indium arsenic antimony (InAsSb).

FIG. 3 is a conceptual diagram showing an example of a band structure in a cross section cut along the line AA (dotted line) shown in FIG. Since the quantum dots 145 have a narrower bandgap than the bulk layer 141, a discretized level (also referred to as a quantum dot level) is formed in the quantum dots 145. Of the electrons that try to pass through the electron barrier layer 14, only the electrons whose energy matches the discretization level in the quantum dots 145 contribute to the conduction through the quantum dots 145. That is, in the photodetector 10 of the present embodiment, the transmittance of electrons inside the electron barrier layer 14 is lowered, and the dark current is suppressed.

It is preferable that the lattice constant of the bulk semiconductor constituting the electron barrier layer 14 is matched with the lattice constant of the material constituting the substrate 11. For example, when the substrate 11 is composed of InP, the lattice constant of the bulk semiconductor constituting the electron barrier layer 14 is matched with the lattice constant of InP (5.8686 angstrom). The condition for lattice matching between the bulk semiconductor constituting the electron barrier layer 14 and the material constituting the substrate 11 (lattice matching condition) is that the difference between the lattice constants of the semiconductor composition of the electron barrier layer 14 and the substrate 11 is 1% or less. It is preferable to have. Further, the difference in the lattice constants of the semiconductor compositions of the electron barrier layer 14 and the substrate 11 is more preferably 0.5% or less, still more preferably 0.2% or less.

For example, the semiconductor composition constituting the electron barrier layer 14 may include other semiconductor compositions within the range of lattice matching with the substrate 11. For example, when InP is used for the substrate 11, phosphorus (P) contained in the substrate 11 may be contained in the electron barrier layer 14. Further, the electron barrier layer 14 may contain a dopant that is not contained in the substrate.

The light receiving layer 15 is laminated on the upper surface of the electron barrier layer 14. For the light receiving layer 15, a material having a good response to desired infrared rays is used. For example, for the light receiving layer 15, a bulk compound semiconductor or a type 2 superlattice structure in which at least two types of compound semiconductors are laminated can be used.

The type 2 superlattice structure has a structure in which at least two types of layers (first light receiving layer and second light receiving layer) are alternately laminated in a short cycle. In the type 2 superlattice structure, a small bandgap is effectively formed by utilizing the transition between mini-bands between the adjacent first light receiving layer and the second light receiving layer. In the type 2 superlattice structure, the places where electrons and holes are confined are spatially different. In other words, in a Type 2 superlattice structure, electrons and holes are alternately confined in different layers.

For example, the light receiving layer 15 can use a type 2 superlattice structure including an indium gallium arsenide (InGaAs) layer as the first light receiving layer and a GaAsSb layer as the second light receiving layer. Hereinafter, a type 2 superlattice structure in which InGaAs layers and GaAsSb layers are alternately laminated will be referred to as InGaAs / GaAsSb.

For example, the light receiving layer 15 having a type 2 superlattice structure can be configured by laminating several hundred pairs of InGaAs / GaAsSb. However, the number of laminated light receiving layers 15 is not limited to those listed here. For example, the light receiving layer 15 having a type 2 superlattice structure is grown on the substrate 11 by using a metalorganic vapor phase growth method, a molecular beam epitaxy method, or a method similar thereto. The light receiving layer 15 may have a type 2 superlattice structure in which three or more types of layers are combined.

In order to maintain high crystal quality of the light receiving layer 15, it is desirable that the lattice constant of the type 2 superlattice structure constituting the light receiving layer 15 matches the lattice constant of the material constituting the substrate 11. The condition for lattice matching between the type 2 superlattice structure constituting the light receiving layer 15 and the material constituting the substrate 11 (lattice matching condition) is that the difference between the lattice constants of the light receiving layer 15 and the substrate 11 is 1% or less. Is preferable. The difference between the lattice constants of the light receiving layer 15 and the substrate 11 is more preferably 0.5% or less, still more preferably 0.2% or less. _{For example, a type 2 superlattice structure containing In 0.52} GaAs as the semiconductor composition of the first light receiving layer and _{GaAs 0.55} Sb as the semiconductor composition of the second light receiving layer can be used as the light receiving layer 15.

Other semiconductor compositions may be added to the light receiving layer 15 as long as the conditions for lattice matching with the materials constituting the substrate 11 are satisfied. Further, the light receiving layer 15 may contain the material contained in the substrate 11. For example, when the semiconductor composition of the substrate 11 is InP, P may be contained in the light receiving layer 15. Further, the light receiving layer 15 may contain a dopant that is not contained in the material of the substrate 11.

The second contact layer 16 is laminated on the upper surface of the light receiving layer 15. The second contact layer 16 contains a dopant. For example, when an n-type dopant is used, Si can be used. For example, when a p-type dopant is used, Be or Zn can be used. The second contact layer 16 preferably has the same composition as the buffer layer 12. The second contact layer 16 may have another semiconductor composition that is lattice-matched with the buffer layer 12. For example, when InP is used as the material of the substrate 11, InGaAs lattice-matched with InP can be used for the second contact layer 16. Since the second contact layer 16 does not necessarily have to be lattice-matched with the substrate 11, the range of material selection is wider than that of the first contact layer 13.

The above is the description of the configuration of the photodetector element 10 of the present embodiment. The configuration of the photodetector element 10 described above is an example, and does not limit the configuration of the photodetector element 10 of the present embodiment.

〔Production method〕
Next, a method of manufacturing the photodetector element 10 will be described with reference to the drawings. FIG. 4 is a flowchart for explaining a method of manufacturing the photodetector element 10.

In FIG. 4, first, the buffer layer 12 is laminated on the upper surface of the substrate 11 (step S11).

Next, the first contact layer 13 is laminated on the upper surface of the buffer layer 12 (step S12). The composition of the first contact layer 13 may be the same as that of the buffer layer 12, or may be another semiconductor composition lattice-matched with the buffer layer 12.

Next, the bulk layer 141 is laminated on the upper surface of the first contact layer 13 (step S13). In step S13, the bulk layers 141 having a film thickness of the electron barrier layer 14 are not laminated at once, but the bulk layers 141 having a thickness corresponding to the position where the quantum dots 145 are formed are laminated.

Next, the quantum dots 145 are formed on the upper surface of the bulk layer 141 in the middle of lamination (step S14). In step S14, the material layer of the quantum dots 145 is thinly laminated on the upper surface of the bulk layer 141 in the middle of lamination. When the difference between the lattice constants of the materials of the bulk layer 141 and the quantum dots 145 is large, the quantum dots 145 are self-formed by the SK (Stranski-Krastanov) growth mode so as to eliminate the distortion of the material layer of the quantum dots 145. To. For example, when AlAs _0.55 Sb is laminated _{as the bulk layer 141 and InAs 0.26} Sb is thinly laminated on the upper surface of _{AlAs 0.55} Sb, the lattice constants differ by 8.5%. Therefore, the quantum dots 145 of _{InAs 0.26 Sb depending on the SK growth mode.} Self-forms.

When forming the quantum dots 145 on the upper surface of the bulk layer 141 in the middle of lamination, the flux is changed. For example, _{when forming the quantum dots 145 of InAs 0.26 Sb while laminating AlAs 0.55} Sb as the bulk layer 141, the As ratio is changed from 0.55 to 0.26 and the Sb ratio is set to 0. Change from 45 to 0.74. For example, when forming quantum dots 145 using the molecular beam epitaxy method, the cell temperature is changed according to the change in flux.

Next, the bulk layer 141 is additionally laminated on the upper surface of the bulk layer 141 on which the quantum dots 145 are formed, and the quantum dots 145 are embedded inside the bulk layer 141 (step S15).

When the electron barrier layer 14 is not completed (No in step S16), the process returns to step S14 to form quantum dots 145 on the upper surface of the bulk layer 141 in the middle of lamination (step S14).

On the other hand, when the electron barrier layer 14 is completed (Yes in step S16), the light receiving layer 15 is laminated on the upper surface of the electron barrier layer 14 (step S17).

Then, the second contact layer 16 is laminated on the upper surface of the light receiving layer 15 (step S18).

The above is the description of the manufacturing method of the photodetector element 10 of the present embodiment. In the method for manufacturing the photodetector 10, when the electron barrier layer 14 is laminated, the steps of intermittently laminating the bulk layer 141 (steps S13 and S15) and the quantum dots on the surface of the bulk layer 141 in the middle of laminating The step of forming 145 (step S14) is repeated. The method for manufacturing the photodetector element 10 according to the flowchart of FIG. 4 is an example, and does not limit the method for manufacturing the photodetector element 10 according to the present embodiment.

[Infrared detection element]
Next, an infrared detection element manufactured by processing the light detection element 10 of the present embodiment will be described with reference to the drawings.

FIG. 5 is a schematic view showing an example of an infrared detection element 100 in which an infrared detection structure formed on the upper surface of a substrate 11 is processed into a plurality of mesa structures 110 (also referred to as detection units). An upper electrode formed on the uppermost surface of the second contact layer 16 is located at the uppermost end of the mesa structure 110.

The mesa structure 110 can be formed by using a microfabrication process such as photolithography or wet etching. If an electrode structure is formed on the upper end of the mesa structure 110 by metal deposition and annealing, an infrared detection element 100 having detection units arranged in an array can be manufactured.

FIG. 6 is a schematic view showing an example of an infrared sensor array 130 configured by flip-chip bonding an infrared detection element 100 to a readout circuit 120. The infrared sensor array 130 can be manufactured by flip-chip bonding the infrared detection element 100 and a readout circuit formed on a silicon substrate.

For example, the manufacturing process of the infrared sensor array 130 is disclosed in Non-Patent Document 5.
(Non-Patent Document 5: HS Kim et al., “Mid-IR focal plane array based on type-II strain layer superlattice detector with nBn design,” Applied Physics Letters, vol.92, 183502, 2008)
In order to operate the infrared detection element 100, a bias voltage is applied between the lower electrode (not shown) formed on the first contact layer 13 and the upper electrode (not shown) formed on the second contact layer 16. .. More specifically, a voltage is applied so that the lower electrode side (first contact layer 13 side) has a negative bias. In the case of a light receiving layer of the type that detects infrared rays by transition between bands, when infrared rays are incident from the back surface of the substrate 11, electrons and holes are generated in the light receiving layer 15. Since a bias voltage is applied between the first contact layer 13 and the second contact layer 16, electrons are conducted to the upper electrode side (second contact layer 16 side), and holes are conducted to the lower electrode side (first contact layer 16 side). Conducts to the contact layer 13 side).

As described above, in the photodetector element of the present embodiment, an electron barrier layer containing quantum dots is sandwiched between the contact layer and the light receiving layer. The electron barrier layer of the photodetector of the present embodiment is configured by self-forming quantum dots having a narrow bandgap semiconductor composition with a longer lattice constant than the semiconductor composition of the electron barrier layer during the lamination of the electron barrier layer. it can. According to the photodetector of the present embodiment, the electron barrier layer containing the quantum dots can reduce the electron transmittance, so that the dark current can be efficiently suppressed.

(Second Embodiment)
Next, the photodetector element according to the second embodiment of the present invention will be described with reference to the drawings. The photodetector of the present embodiment is different from the first embodiment in that quantum dots are included inside the electron barrier layer having a type 1 superlattice structure. In the following, description of the same configuration and function as the photodetector 10 of the first embodiment may be omitted.

FIG. 7 is a schematic view showing an example of the configuration of the photodetector element 20 of the present embodiment. As shown in FIG. 7, the photodetector 20 includes a substrate 21, a buffer layer 22, a first contact layer 23, an electron barrier layer 24, a light receiving layer 25, and a second contact layer 26. Note that FIG. 7 conceptually shows the configuration of the photodetector element 20, and does not accurately represent the scale of each configuration.

The substrate 21 is a substrate for forming an infrared detection structure. The substrate 21 is the same as the substrate 11 of the first embodiment.

The buffer layer 22 is formed on the upper surface of the substrate 21. The buffer layer 22 is the same as the buffer layer 12 of the first embodiment.

The first contact layer 23 is formed on the upper surface of the buffer layer 22. The first contact layer 23 is the same as the first contact layer 13 of the first embodiment.

The electron barrier layer 24 is laminated on the upper surface of the first contact layer 23. The electron barrier layer 24 has a type 1 superlattice structure including quantum dots. The type 1 superlattice structure has a structure in which a layer composed of a semiconductor composition having a first bandgap sandwiches a layer composed of a semiconductor composition having a second bandgap narrower than the first bandgap. Have. In the type 1 superlattice structure, the place where electrons and holes are confined is spatially the same. The type 1 superlattice structure included in the electron barrier layer 24 has a structure in which at least two types of layers are alternately laminated in a short cycle. In the following, an electron barrier layer 24 including a type 1 superlattice structure in which two types of layers are alternately laminated will be described as an example. The electron barrier layer 24 may be formed by combining three or more types of layers.

FIG. 8 is a conceptual diagram showing an example of the configuration of the electron barrier layer 24. As shown in FIG. 8, the electron barrier layer 24 has a first barrier layer 241 composed of a semiconductor composition having a first bandgap and a second barrier layer 242 composed of a semiconductor composition having a second bandgap. It has a type 1 superlattice structure in which and are alternately laminated. The quantum dots 245 are formed on the upper surface of the first barrier layer 241 and are embedded inside the second barrier layer 242 (corresponding to the well layer). The quantum dots 245 have a third bandgap that is narrower than the second barrier layer 242. The quantum dots 245 are naturally arranged so that the distortion of the interface is eliminated when a semiconductor composition having a lattice constant larger than that of the material of the first barrier layer 241 is laminated in the middle of crystal growth of the electron barrier layer 24. It is formed. The quantum dots 245 may be formed anywhere inside the second barrier layer, but in the present embodiment, an example of forming the quantum dots 245 immediately after the growth of the first barrier layer 241 is shown.

As the quantum dot 245, InSb, InGaSb, InAsSb and the like can be used as in the first embodiment. In the following, an electron barrier layer 24 including an AlAsSb / GaAsSb superlattice having AlAsSb as the first barrier layer 241 and GaAsSb as the second barrier layer 242 as a type 1 superlattice will be given as an example.

For example, when an InP substrate is used as the substrate 21 and an InGaAs / GaAs _{0.55 Sb superlattice having a type 2 superlattice structure is used as the light receiving layer 25, an AlAs 0.55} Sb / GaAs _0.55 Sb superlattice that is lattice-matched with those layers is used as an electronic barrier. It can be used as the layer 24. _{When InAs 0.26} Sb is thinly laminated immediately after the growth of the first barrier layer 241 (AlAsSb), the quantum dots 245 composed of InAsSb are self-formed. Then, by laminating the second barrier layer (GaAsSb) on the upper surface of the first barrier layer 241 (AlAsSb) on which the quantum dots 245 are formed, the second barrier layer (GaAsSb) containing the quantum dots 245 (InAsSb) is formed. Can be formed.

_{For example, when GaAs 0.55} Sb is used as the second barrier layer 242 _{, InAa 0.26} Sb can be configured as quantum dots 245. When the As ratio of InAaSb is 0.26, _{the valence band ends of GaAs 0.55} Sb and InAsSb coincide with each other. When _{the valence band ends of InAa 0.26} Sb and GaAs _0.55 Sb coincide with each other, the second barrier layer 242 and the quantum dots 245 have the same potential for holes. Therefore, for holes, when the quantum level is not formed in the quantum dots 245 and the light receiving layer 25 has a type 2 superlattice structure, the hole miniband of the electron barrier layer 24 and the positive light receiving layer 25 are positive. The hole mini-band can be formed continuously.

On the other hand, InAs _0.26 Sb is _{a well with a deeper potential than GaAs 0.55} Sb, so a quantum level is formed for electrons. Of the electrons that try to pass through the inside of the electron barrier layer 24, only the electrons whose energy matches the quantum level contribute to the conduction through the quantum dots 245. As a result, the electron transmittance of the electron barrier layer 24 decreases, and the dark current is suppressed.

For example, it is preferable that the lattice constant of the type 1 superlattice structure constituting the electron barrier layer 24 is matched with the lattice constant of the material constituting the substrate 21. When the substrate 21 is composed of InP, the lattice constant of the type 1 superlattice structure constituting the electron barrier layer 24 is matched with the lattice constant of InP (5.8686 angstrom). The condition for lattice matching between the type 1 superlattice structure constituting the electron barrier layer 24 and the material constituting the substrate 21 (lattice matching condition) is that the difference in lattice constant between the semiconductor composition of the electron barrier layer 24 and the substrate 21 is 1. It is preferably less than a percentage. Further, the difference in the lattice constants of the semiconductor compositions of the electron barrier layer 24 and the substrate 21 is more preferably 0.5% or less, still more preferably 0.2% or less.

For example, the type 1 superlattice structure constituting the electron barrier layer 24 may contain other semiconductor compositions within the range of lattice matching with the substrate 21. For example, when an InP substrate is used as the substrate 21, the electron barrier layer 24 may contain phosphorus (P) contained in the substrate 21.

The As ratio in the second barrier layer (GaAsSb) of the electron barrier layer 24 may be any value as long as it is lattice-matched with the substrate 21. For example, the As ratio in the second barrier layer (GaAsSb) of the electron barrier layer 24 can be set to 0.55.

On the other hand, the optimum value of the As ratio of the first barrier layer (AlAsSb) of the electron barrier layer 24 is around 0.56. This is because when the lattice constant of AlAs (5.6605 angstrom) and the lattice constant of AlSb (6.1355 angstrom) are linearly interpolated, the As ratio matches the lattice constant of InP (5.8686 angstrom) at around 0.56. Because it does. AlAs _0.55 Sb is estimated to have a difference in lattice constant from InP of about 0.1%, and satisfies the most preferable lattice matching condition (0.2% or less) among the above-mentioned lattice matching conditions. The As ratio of the first barrier layer (AlAsSb) of the electron barrier layer 14 is not limited to 0.55.

FIG. 9 is a conceptual diagram showing an example of a band structure in a cross section cut along the BB line (dotted line) shown in FIG. Since the quantum dot 245 has a narrow band gap, a discretized level (also referred to as a quantum dot level) is formed in the quantum dot 245. Of the electrons that are going to pass through the electron barrier layer 24, only the electrons whose energy matches the discretization level in the quantum dots 245 contribute to the conduction through the quantum dots 245. That is, in the photodetector 20 of the present embodiment, the transmittance of electrons inside the electron barrier layer 24 is lowered, and the dark current is suppressed.

The light receiving layer 25 is laminated on the upper surface of the electron barrier layer 24. The light receiving layer 25 is the same as the light receiving layer 15 of the first embodiment.

The second contact layer 26 is laminated on the upper surface of the light receiving layer 25. The second contact layer 26 is the same as the second contact layer 16 of the first embodiment.

The above is the description of the configuration of the photodetector element 20 of the present embodiment. The configuration of the photodetector element 20 described above is an example, and does not limit the configuration of the photodetector element 20 of the present embodiment.

〔Production method〕
Next, a method of manufacturing the photodetector element 20 will be described with reference to the drawings. FIG. 10 is a flowchart for explaining a method of manufacturing the photodetector element 20.

In FIG. 10, first, the buffer layer 22 is laminated on the upper surface of the substrate 21 (step S21).

Next, the first contact layer 23 is laminated on the upper surface of the buffer layer 22 (step S22). The composition of the first contact layer 23 may be the same as that of the buffer layer 22, or may be another semiconductor composition lattice-matched with the buffer layer 22.

Next, the first barrier layer 241 is laminated on the upper surface of the first contact layer 13 (step S23).

Next, quantum dots 245 are formed on the upper surface of the first barrier layer 241 (step S24). In step S24, the material layer of the quantum dots 245 is thinly laminated on the upper surface of the first barrier layer 241. When the difference between the lattice constants of the material of the first barrier layer 241 and the material of the quantum dot 245 is large, the quantum dot 245 is self-formed by the SK growth mode so as to eliminate the distortion of the material layer of the quantum dot 245. _{For example, when AlAs 0.55} Sb is laminated as the first barrier layer 241 _{and InAs 0.26} Sb is thinly laminated on the upper surface of _{AlAs 0.55} Sb, the lattice constants differ by 8.5%, so that the quantum of _{InAs 0.26 Sb depends on the SK growth mode.} Dots 245 self-form.

When forming the quantum dots 245 on the upper surface of the first barrier layer 241, the flux is changed. For example, _{when forming quantum dots 245 of InAs 0.26 Sb while laminating AlAs 0.55} Sb as the first barrier layer 241, the As ratio is changed from 0.55 to 0.26 and the Sb ratio is changed. Change from 0.45 to 0.74. Therefore, for example, when forming quantum dots 245 using the molecular beam epitaxy method, the cell temperature is changed in order to change the flux.

Next, the second barrier layer 242 is laminated on the upper surface of the first barrier layer 241 on which the quantum dots 245 are formed, and the quantum dots 245 are embedded inside the second barrier layer 242 (step S25).

Next, the first barrier layer 241 is laminated on the upper surface of the second barrier layer 242 (step S26).

If the electronic barrier layer 24 is not completed (No in step S27), the process returns to step S24 to form quantum dots 245 on the upper surface of the first barrier layer 241 (step S24).

On the other hand, when the electron barrier layer 24 is completed (Yes in step S27), the light receiving layer 25 is laminated on the upper surface of the electron barrier layer 24 (step S28).

Then, the second contact layer 26 is laminated on the upper surface of the light receiving layer 25 (step S29).

The above is the description of the manufacturing method of the photodetector 20 of the present embodiment. In the method for manufacturing the photodetector layer 20, when the electron barrier layer 24 is laminated, the step of laminating the first barrier layer 241, the step of forming the quantum dots 245 on the surface of the first barrier layer 241 and the second step. The process of embedding the quantum dots 245 inside the barrier layer 242 is repeated. The method for manufacturing the photodetector element 20 according to the flowchart of FIG. 10 is an example, and does not limit the method for manufacturing the photodetector element 20 according to the present embodiment.

As described above, the photodetector element of the present embodiment sandwiches an electron barrier layer having a type 1 superlattice structure containing quantum dots between the contact layer and the light receiving layer. The electron barrier layer of the photodetector of the present embodiment has a lattice constant inside the second barrier layer constituting the electron barrier layer of the type 1 superlattice structure, rather than the semiconductor composition of the first barrier layer and the second barrier layer. It can be constructed by self-forming quantum dots having a long, narrow bandgap semiconductor composition.

For example, the electron barrier layer is a first barrier layer composed of a semiconductor composition having a first bandgap and a second barrier composed of a semiconductor composition having a second bandgap narrower than the first bandgap. It has a type 1 superlattice structure in which pairs with layers are laminated. The second barrier layer contains quantum dots having a semiconductor composition having a third bandgap narrower than the second bandgap and having a lattice constant larger than the semiconductor composition of the first barrier layer and the second barrier layer. For example, the electron barrier layer contains quantum dots self-formed on the upper surface of the first barrier layer.

For example, the light receiving layer has a type 2 superlattice structure in which a pair of a first light receiving layer and a second light receiving layer is laminated. For example, the quantum dots and the valence band of the second barrier layer match, and either the valence band edge of the light receiving layer or the hole miniband coincides with the hole miniband of the electron barrier layer.

For example, in the light receiving layer, the semiconductor composition of the first light receiving layer contains InGaAs, and the semiconductor composition of the second light receiving layer contains GaAsSb. For example, in the light receiving layer, the semiconductor composition of the first light receiving layer _{contains In 0.52} GaAs, and the semiconductor composition of the second light receiving layer contains GaAs _0.55 Sb. For example, in the electron barrier layer, the semiconductor composition of the first barrier layer contains AlAsSb, the semiconductor composition of the second barrier layer contains GaAsSb, and the semiconductor composition of the quantum dots contains InAsSb. For example, in the electron barrier layer, the ratio of As in the group V elements of the semiconductor composition of the first barrier layer and the second barrier layer is equal. The Group V element is a general term for elements belonging to Group 15 of the Periodic Table of the Elements. For example, As, Sb, P and the like are typical Group V elements. For example, in the electron barrier layer, the semiconductor composition of the first barrier layer _{contains AlAs 0.55} Sb, the semiconductor composition of the second barrier layer _{contains GaAs 0.55} Sb, and the semiconductor composition of the quantum dots contains InAs _0.26 Sb.

According to the photodetector of the present embodiment, since the electron barrier layer of the type 1 superlattice structure contains quantum dots, the electron transmittance in the electron barrier layer is lowered as compared with the first embodiment, resulting in darkening. The current can be further suppressed.

(Third Embodiment)
Next, the photodetector 30 according to the third embodiment of the present invention will be described with reference to the drawings. The photodetector element 30 of the present embodiment has a configuration in which the photodetector element 10 of the first embodiment and the photodetector element 20 of the second embodiment are super-conceptualized.

FIG. 11 is a conceptual diagram showing an example of the configuration of the photodetector element 30 of the present embodiment. As shown in FIG. 11, the photodetector element 30 includes a substrate 31, an electron barrier layer 34, and a light receiving layer 35.

The substrate 31 is a substrate for forming an infrared detection structure. The substrate 31 is the same as the substrate 11 of the first embodiment.

The electron barrier layer 34 is formed in contact with the light receiving layer 35 and includes a plurality of quantum dots 345. The base material of the electron barrier layer 34 and the semiconductor composition constituting the quantum dots 345 have different lattice constants. The electron barrier layer 34 is similar to the electron barrier layer 14 of the first embodiment or the electron barrier layer 24 of the second embodiment.

For example, the electron barrier layer 34 includes a bulk semiconductor in which a plurality of quantum dots 345 are embedded. The semiconductor composition of the quantum dots 345 has a narrow bandgap and a large lattice constant than the bulk semiconductor.

For example, a bulk semiconductor is composed of a semiconductor composition of AlGaSb, and a quantum dot 345 is composed of a semiconductor composition selected from the group consisting of InSb, InGaSb, and InAsSb.

For example, the electron barrier layer 34 is composed of a type 1 superlattice structure in which a plurality of quantum dots 345 are embedded. For example, the electron barrier layer 34 has a first barrier layer composed of a semiconductor composition having a first bandgap and a second barrier layer composed of a semiconductor composition having a second bandgap narrower than the first bandgap. It has a type 1 superlattice structure in which a pair with a barrier layer is laminated. For example, the second barrier layer includes quantum dots 345 having a semiconductor composition having a third bandgap narrower than the second bandgap and having a lattice constant larger than the semiconductor composition of the second barrier layer. For example, the electron barrier layer 34 includes quantum dots 345 self-formed on the upper surface of the first barrier layer.

For example, in the electron barrier layer 34, the semiconductor composition of the first barrier layer contains AlAsSb, the semiconductor composition of the second barrier layer contains GaAsSb, and the semiconductor composition of the quantum dots contains InAsSb. For example, in the electron barrier layer 34, the ratio of As in the group V elements of the semiconductor composition of the first barrier layer and the second barrier layer is equal.

The light receiving layer 35 is formed above the substrate 31 and is formed in contact with the electron barrier layer 34. The light receiving layer 35 is the same as the light receiving layer 15 of the first embodiment. The light receiving layer 35 does not have to be in contact with the upper surface of the substrate 31, and is formed above the substrate 31 with a buffer layer and a contact layer (not shown) interposed therebetween.

For example, the light receiving layer 35 has a superlattice structure in which a pair of a first light receiving layer and a second light receiving layer having different band gaps are laminated.

For example, in the electron barrier layer 34, the semiconductor composition of the first barrier layer _{contains AlAs 0.55} Sb, the semiconductor composition of the second barrier layer _{contains GaAs 0.55} Sb, and the semiconductor composition of the quantum dots contains InAs _0.26 Sb. For example, in the light receiving layer 35, the semiconductor composition of the first light receiving layer _{contains In 0.52} GaAs, and the semiconductor composition of the second light receiving layer contains GaAs _0.55 Sb.

For example, at least one of the electron barrier layer 34 and the light receiving layer 35 contains P.

For example, the photodetector 30 includes two contact layers that sandwich an electron barrier layer 34 and a light receiving layer 35, and at least one of the two contact layers contains an n-type dopant. For example, the photodetector 30 is provided between one of the two contact layers and the substrate 31 with a buffer layer made of the same material as the substrate 31 and crystal-grown according to the plane orientation of the substrate 31.

According to the photodetector of the present embodiment, it is possible to provide a photodetector in which the generation of dark current is suppressed, as in the first and second embodiments.

(Fourth Embodiment)
Next, the infrared detection device (also referred to as an infrared camera) according to the fourth embodiment of the present invention will be described with reference to the drawings. The infrared detection device of this embodiment includes a photodetector according to any one of the first to third embodiments.

FIG. 12 is a conceptual diagram showing an example of the configuration of the infrared detection device 40 of the present embodiment. As shown in FIG. 12, the infrared detection device 40 includes an infrared optical system 41, an infrared detection element 42, a readout circuit 43, and an output circuit 44.

The infrared optical system 41 includes a lens that collects infrared light in a light receiving portion of the infrared detection element 42. The infrared optical system 41 includes at least one lens. The lens of the infrared optical system 41 has a high transmittance of infrared light, and is made of a material that refracts infrared light on the light receiving surface of the infrared detection element 42. For example, germanium, silicon, zinc sulfide, zinc selenide, chalcogenide glass, and the like can be applied to the lens material of the infrared optical system 41. The lens of the infrared optical system 41 may be selected according to the wavelength of the infrared light to be detected. The infrared optical system 41 may include a filter that blocks or transmits light in a specific wavelength region. Further, the infrared optical system 41 may include a reflector for guiding infrared light to the light receiving portion of the infrared detection element 42, and a diaphragm for controlling the amount of infrared light.

The infrared detection element 42 has an infrared light detection structure formed by processing the light detection elements of the first to third embodiments into an array. In other words, the infrared detection element 42 has an array of detection units in which, for example, a light receiving layer having a type 2 superlattice structure and an electron barrier layer having a type 1 superlattice structure are laminated on a substrate having a high transmittance for desired infrared rays. It has a structure arranged in. Each of the plurality of detection units constituting the infrared photodetection structure of the infrared detection element 42 processed in an array independently detects infrared rays. Each of the plurality of detection units constituting the infrared light detection structure of the infrared detection element 42 processed in an array corresponds to the pixel of the infrared image.

The readout circuit 43 is connected to the infrared detection element 42. For example, the readout circuit 43 is flip-chip bonded to the infrared detection element 42 as shown in FIG. The infrared sensor array is composed of the infrared detection element 42 and the readout circuit 43. The reading circuit 43 reads infrared rays detected by the infrared detecting element 42 for each detection unit (pixel) of the infrared detecting element 42.

The output circuit 44 outputs a signal based on the infrared light detected by the readout circuit 43. For example, the output circuit 44 outputs a signal based on the infrared light detected by the readout circuit 43 to an external system. For example, the output circuit 44 may generate an infrared image from a signal based on the infrared light detected by the readout circuit 43, and display the generated infrared image on a monitor installed in its own device.

The infrared detection device 40 may include a cooling device that cools the infrared detection element 42. For example, a Peltier element or the like can be used as a cooling device for cooling the infrared detection element 42. If the infrared detection element 42 is cooled to a low temperature, thermal noise can be reduced and the sensitivity is improved. Further, if the infrared detection element 42 is cooled to a low temperature, the response speed to infrared light can be maintained.

As described above, according to the present embodiment, it is possible to provide an infrared camera equipped with a photodetector element having high sensitivity to infrared rays in a desired wavelength region and suppressing the generation of dark current.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the present invention.

Some or all of the above embodiments may also be described, but not limited to:
(Appendix 1)
With the board
A light receiving layer formed above the substrate and
An electron barrier layer formed in contact with the light receiving layer and containing a plurality of quantum dots is provided.
A photodetector whose lattice constant is different between the semiconductor base material of the electron barrier layer and the semiconductor constituting the quantum dot.
(Appendix 2)
The electron barrier layer is
Including a bulk semiconductor in which the plurality of the quantum dots are embedded,
The photodetector according to Appendix 1, wherein the quantum dot semiconductor has a narrower bandgap and a larger lattice constant than the bulk semiconductor.
(Appendix 3)
The bulk semiconductor is
Consists of AlGaSb semiconductors
The quantum dots are
The photodetector according to Appendix 2, which is composed of a semiconductor selected from the group consisting of InSb, InGaSb, and InAsSb.
(Appendix 4)
The bulk semiconductor is
Consists of AlGaSb semiconductors
The quantum dots are
The photodetector according to Appendix 2, which is composed of an InAsSb semiconductor.
(Appendix 5)
The electron barrier layer is
The photodetector according to Appendix 1, which is composed of a type 1 superlattice structure in which a plurality of the quantum dots are embedded.
(Appendix 6)
The electron barrier layer is
A pair of a first barrier layer composed of a semiconductor having a first bandgap and a second barrier layer composed of a semiconductor having a second bandgap narrower than the first bandgap was laminated. Has a type 1 superlattice structure,
The second barrier layer is
The appendix 5 comprising the quantum dots of a semiconductor having a third bandgap narrower than the second bandgap and having a lattice constant larger than that of the semiconductor of the first barrier layer and the second barrier layer. Light detection element.
(Appendix 7)
The electron barrier layer is
The photodetector according to Appendix 6, which includes the quantum dots self-formed on the upper surface of the first barrier layer.
(Appendix 8)
The light receiving layer is
The photodetector according to any one of Supplementary note 1 to 7, which has a superlattice structure in which a pair of a first light receiving layer and a second light receiving layer having different band gaps are laminated.
(Appendix 9)
The light receiving layer is
It has a type 2 superlattice structure in which a pair of a first light receiving layer and a second light receiving layer are laminated.
The quantum dot and the valence band of the second barrier layer coincide with each other, and any of the valence band edge and the hole miniband of the light receiving layer and the hole miniband of the electron barrier layer substantially coincide with each other. 7. The light detection element according to 7.
(Appendix 10)
The light receiving layer is
The semiconductor of the first light receiving layer contains InGaAs and contains InGaAs.
The photodetector according to Appendix 9, wherein the semiconductor of the second light receiving layer contains GaAsSb.
(Appendix 11)
The light receiving layer is
The semiconductor of the first light receiving layer _{contains In 0.52} GaAs and contains In 0.52 GaAs.
The photodetector according to Appendix 9, wherein the semiconductor of the second light receiving layer _{contains GaAs 0.55 Sb.}
(Appendix 12)
The electron barrier layer is
The semiconductor of the first barrier layer contains AlAsSb and contains
The semiconductor of the second barrier layer contains GaAsSb and contains
The photodetector according to any one of Supplementary note 9 to 11, wherein the quantum dot semiconductor contains InAsSb.
(Appendix 13)
The electron barrier layer is
The photodetector according to Appendix 12, wherein the ratio of As in the group V elements of the semiconductor of the first barrier layer and the second barrier layer is the same.
(Appendix 14)
The electron barrier layer is
The semiconductor of the first barrier layer _{contains AlAs 0.55} Sb and contains.
The semiconductor of the second barrier layer _{contains GaAs 0.55} Sb and contains.
The photodetector according to any one of Supplementary note 9 to 11, wherein the quantum dot semiconductor _{contains InAs 0.26 Sb.}
(Appendix 15)
The photodetector according to any one of Supplementary note 1 to 14, wherein at least one of the electron barrier layer and the light receiving layer contains P.
(Appendix 16)
The two contact layers that sandwich the electron barrier layer and the light receiving layer are provided.
The photodetector according to any one of Appendix 1 to 15, wherein at least one of the two contact layers contains an n-type dopant.
(Appendix 17)
The photodetector according to Appendix 16, further comprising a buffer layer between one of the two contact layers and the substrate, which is made of the same material as the substrate and crystal-grown in accordance with the plane orientation of the substrate.
(Appendix 18)
The photodetector according to any one of Supplementary note 1 to 17, wherein the detection unit including at least the electron barrier layer and the light receiving layer has an infrared detection structure in which the detection units are arranged in an array on a substrate.
(Appendix 19)
The photodetector according to Appendix 18,
A readout circuit that is flip-chip bonded to the photodetector and reads out infrared light detected by the photodetector for each detection unit.
An infrared optical system that converges infrared light on the infrared detection structure of the photodetector,
An infrared detection device including an output circuit that outputs a signal based on infrared light detected for each detection unit.

10, 20, 30 Photodetector 11, 21, 31 Substrate 12, 22 Buffer layer 13, 23 First contact layer 14, 24, 34 Electronic barrier layer 15, 25, 35 Light receiving layer 16, 26 Second contact layer 40 Infrared Detection device 41 Infrared optical system 42 Infrared detection element 43 Read circuit 44 Output circuit 141 Bulk layer 145, 245, 345 Quantum dots 241 First barrier layer 242 Second barrier layer

Claims (19)

With the board
A light receiving layer formed above the substrate and
An electron barrier layer formed in contact with the light receiving layer and containing a plurality of quantum dots is provided.
A photodetector whose lattice constant is different between the semiconductor base material of the electron barrier layer and the semiconductor constituting the quantum dot. The electron barrier layer is
Including a bulk semiconductor in which the plurality of the quantum dots are embedded,
The photodetector according to claim 1, wherein the quantum dot semiconductor has a narrower bandgap and a larger lattice constant than the bulk semiconductor. The bulk semiconductor is
Consists of AlGaSb semiconductors
The quantum dots are
The photodetector according to claim 2, wherein the photodetector is composed of a semiconductor selected from the group consisting of InSb, InGaSb, and InAsSb. The bulk semiconductor is
Consists of AlGaSb semiconductors
The quantum dots are
The photodetector according to claim 2, which is made of a semiconductor of InAsSb. The electron barrier layer is
The photodetector according to claim 1, further comprising a type 1 superlattice structure in which a plurality of the quantum dots are embedded. The electron barrier layer is
A pair of a first barrier layer composed of a semiconductor having a first bandgap and a second barrier layer composed of a semiconductor having a second bandgap narrower than the first bandgap was laminated. Has a type 1 superlattice structure,
The second barrier layer is
The fifth aspect of claim 5 includes the quantum dots of a semiconductor having a third bandgap narrower than the second bandgap and having a lattice constant larger than that of the semiconductor of the first barrier layer and the second barrier layer. Light detection element. The electron barrier layer is
The photodetector according to claim 6, further comprising the quantum dots self-formed on the upper surface of the first barrier layer. The light receiving layer is
The photodetector according to any one of claims 1 to 7, which has a superlattice structure in which a pair of a first light receiving layer and a second light receiving layer having different band gaps are laminated. The light receiving layer is
It has a type 2 superlattice structure in which a pair of a first light receiving layer and a second light receiving layer are laminated.
6. The quantum dot and the valence band of the second barrier layer match, and any one of the valence band edge and the hole miniband of the light receiving layer and the hole miniband of the electron barrier layer substantially match. Or the light detection element according to 7. The light receiving layer is
The semiconductor of the first light receiving layer contains InGaAs and contains InGaAs.
The photodetector according to claim 9, wherein the semiconductor of the second light receiving layer includes GaAsSb. The light receiving layer is
The semiconductor of the first light receiving layer _{contains In 0.52} GaAs and contains In 0.52 GaAs.
The photodetector according to claim 9, wherein the semiconductor of the second light receiving layer _{includes GaAs 0.55 Sb.} The electron barrier layer is
The semiconductor of the first barrier layer contains AlAsSb and contains
The semiconductor of the second barrier layer contains GaAsSb and contains
The photodetector according to any one of claims 9 to 11, wherein the quantum dot semiconductor includes InAsSb. The electron barrier layer is
The photodetector according to claim 12, wherein the ratio of As in the group V elements of the semiconductor of the first barrier layer and the second barrier layer is the same. The electron barrier layer is
The semiconductor of the first barrier layer _{contains AlAs 0.55} Sb and contains.
The semiconductor of the second barrier layer _{contains GaAs 0.55} Sb and contains.
The photodetector according to any one of claims 9 to 11, wherein the quantum dot semiconductor _{contains InAs 0.26 Sb.} The photodetector according to any one of claims 1 to 14, wherein at least one of the electron barrier layer and the light receiving layer contains P. The two contact layers that sandwich the electron barrier layer and the light receiving layer are provided.
The photodetector according to any one of claims 1 to 15, wherein at least one of the two contact layers contains an n-type dopant. The photodetector according to claim 16, further comprising a buffer layer formed of the same material as the substrate and crystal-grown in accordance with the plane orientation of the substrate between any of the two contact layers and the substrate. The photodetector according to any one of claims 1 to 17, which has an infrared detection structure in which detection units including at least the electron barrier layer and the light receiving layer are arranged in an array on a substrate. The photodetector according to claim 18,
A readout circuit that is flip-chip bonded to the photodetector and reads out infrared light detected by the photodetector for each detection unit.
An infrared optical system that converges infrared light on the infrared detection structure of the photodetector,
An infrared detection device including an output circuit that outputs a signal based on infrared light detected for each detection unit.

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