light-receiving element

Abstract

To provide a light receiving element having high light reception sensitivity.SOLUTION: A light receiving element comprises a base substrate. The light receiving element comprises a first conductive type first semiconductor film arranged on the base substrate. The light receiving element comprises a second conductive type second semiconductor film arranged on the first semiconductor film. The light receiving element comprises a first electrode in contact with the first semiconductor film. The light receiving element comprises a second electrode in contact with the second semiconductor film. A band gap of the second semiconductor film is larger than that of the first semiconductor film. The first semiconductor film is a semiconductor absorbing an infrared radiation. The second semiconductor film is a semiconductor transmitting the infrared radiation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a light-receiving element.

Background Art

[0002] Patent Document 1 discloses a light-receiving element including a semiconductor substrate made of n-type silicon and a light-receiving film made of p-type germanium provided on the semiconductor substrate. In this light-receiving element, a depletion layer is formed at the pn junction between the semiconductor substrate and the light-receiving film. When the depletion layer is irradiated with light, photoexcited electrons and holes are generated. The generated electrons and holes are separated by the electric field applied to the depletion layer and taken out as a photocurrent to an external circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The semiconductor substrate and the light-receiving film are made of different materials. Therefore, a large number of crystal defects caused by lattice mismatch are included on the light-receiving film side of the pn junction between the semiconductor substrate and the light-receiving film. Such crystal defects can act as carriers. Therefore, a region with a high carrier concentration is formed in the light-receiving film of the pn junction. Such a region with a high carrier concentration in the light-receiving film suppresses the spread of the depletion layer into the light-receiving film and causes a decrease in light-receiving sensitivity. The purpose of this specification is to provide a light-receiving element with high light-receiving sensitivity.

Means for Solving the Problems

[0005] One embodiment of a photodetector disclosed herein comprises a base substrate, a first semiconductor film of a first conductivity type disposed on the base substrate, a second semiconductor film of a second conductivity type disposed on the first semiconductor film, a first electrode in contact with the first semiconductor film, and a second electrode in contact with the second semiconductor film. The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared light. The second semiconductor film is a semiconductor that transmits infrared light.

[0006] In the above-described photodetector, a pn junction can be formed between the upper part of the first semiconductor film and the lower part of the second semiconductor film. Since the second semiconductor film transmits infrared light and the first semiconductor film absorbs infrared light, infrared light can be received at the upper part of the first semiconductor film via the second semiconductor film. In other words, the upper part of the first semiconductor film can function as a photodetector. The upper part of the first semiconductor film is further from the base substrate than the lower part of the first semiconductor film. Therefore, the upper part of the first semiconductor film has fewer crystal defects caused by the base substrate than the lower part. By forming a photodetector at the upper part of the first semiconductor film, which has fewer crystal defects, the carrier concentration caused by crystal defects can be reduced in the photodetector. Since the depletion layer can be extended more widely in the photodetector, it is possible to improve the photodetector sensitivity.

[0007] One embodiment of a photodetector disclosed herein is a photodetector comprising: a base substrate of a semiconductor of a first conductivity type; a first semiconductor film of the first conductivity type disposed on the base substrate; a second semiconductor film of a second conductivity type disposed on the first semiconductor film; a first electrode in contact with the first semiconductor film; and a second electrode in contact with the second semiconductor film. The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared light. The second semiconductor film is a semiconductor that transmits infrared light. Details of the effects will be described in the examples.

[0008] One embodiment of a photodetector disclosed herein comprises a p-type semiconductor base substrate, a first p-type semiconductor film disposed on the base substrate, a second n-type semiconductor film disposed on the first semiconductor film, a first electrode in contact with the first semiconductor film, and a second electrode in contact with the second semiconductor film. The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared light. The second semiconductor film is a semiconductor that transmits infrared light. Details of the effects will be described in the examples.

[0009] One embodiment of a photodetector disclosed herein comprises a p-type semiconductor base substrate, a first p-type semiconductor film disposed on the base substrate, a second n-type semiconductor film disposed on a portion of the surface of the first semiconductor film, a first electrode disposed in contact with the surface of the first semiconductor film where the second semiconductor film is not disposed, a second electrode in contact with the second semiconductor film, and an insulating portion disposed in contact with the first electrode and the second electrode. The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared light. The second semiconductor film is a semiconductor that transmits infrared light. Details of the effects will be described in the examples.

[0010] The first semiconductor film may be a semiconductor containing Ge.

[0011] The second electrode is located on at least a portion of the surface of the second semiconductor film and may be made of a material that transmits infrared light.

[0012] The first semiconductor film may be GeSn. The second semiconductor film may be a transparent oxide semiconductor.

[0013] The second semiconductor film may be located on a portion of the surface of the first semiconductor film. The first electrode may be located in contact with the surface of the first semiconductor film where the second semiconductor film is not located. The second electrode may be located on at least a portion of the surface of the second semiconductor film. The second electrode may be located such that it includes at least a portion of the edge of the second semiconductor film when viewed from vertically above the surface of the second semiconductor film. The photodetector may further include an insulating portion located in contact with the first electrode and the second electrode. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic cross-sectional view of the light-receiving element according to Example 1. [Figure 2] This is a schematic cross-sectional view of the light-receiving element according to Example 2. [Figure 3] This diagram illustrates the manufacturing process of the light-receiving element according to Example 2. [Figure 4] This is a schematic cross-sectional view of a modified photodetector. [Modes for carrying out the invention] [Examples]

[0015] Figure 1(A) shows a schematic cross-sectional view of the photodetector 1 of Example 1. The photodetector 1 is a heterojunction photodiode with a first semiconductor film 20 as the photodetector. The photodetector 1 comprises a base substrate 10, a first semiconductor film 20, a second semiconductor film 30, a first electrode 40, and a second electrode 50.

[0016] The base substrate 10 is a substrate having a crystal structure with a lattice constant close to that of the first semiconductor film 20. The material of the base substrate 10 is not particularly limited. In this embodiment, the base substrate 10 is a silicon single crystal. The conductivity type of the base substrate 10 is not particularly limited and can be any conductivity type such as n-type, p-type, or i-type. In this embodiment, the base substrate 10 is p-type.

[0017] On the base substrate 10, a first semiconductor film 20 is disposed. The first semiconductor film 20 is a semiconductor having a smaller bandgap than the second semiconductor film 30. The first semiconductor film 20 may be a single crystal epitaxially grown on the base substrate 10. The first semiconductor film 20 is a semiconductor that absorbs infrared light. Here, infrared light is light having a wavelength in the range from 780 nm to about 1 mm. Particularly preferably, it is eye-safe band light (light of 1300 nm to 2600 nm).

[0018] The material of the first semiconductor film 20 is not particularly limited. For example, the first semiconductor film 20 may be a semiconductor containing Ge. Examples of the material of the first semiconductor film 20 include Ge, GeSn, GaSb, InN, and the like. In this embodiment, the first semiconductor film 20 is made of GeSn. The infrared absorption wavelength of GeSn with the addition of Sn (about 1.7 μm) can be made longer than the infrared absorption wavelength of Ge alone (about 1.5 μm). Also, the conductivity type of the first semiconductor film 20 is not particularly limited. For example, the conductivity type of the first semiconductor film 20 can be the same as the conductivity type of the base substrate 10. In this embodiment, the first semiconductor film 20 is made p-type.

[0019] On the first semiconductor film 20, a second semiconductor film 30 is disposed. The second semiconductor film 30 is a semiconductor having a larger bandgap than the first semiconductor film 20. Also, the second semiconductor film 30 is a semiconductor that transmits infrared light. The second semiconductor film 30 may be a single crystal epitaxially grown on the first semiconductor film 20.

[0020] The material of the second semiconductor film 30 is not particularly limited. For example, the second semiconductor film 30 may be a transparent oxide semiconductor. Examples of the material of the second semiconductor film 30 include oxide semiconductors such as InO, SnO, and ZnO-based. In this embodiment, the second semiconductor film 30 is made of GZO (GaZnO). Also, the conductivity type of the second semiconductor film 30 is different from the conductivity type of the first semiconductor film 20. In this embodiment, the second semiconductor film 30 is made n-type. A heterojunction pn junction J1 is formed by the junction surface between the upper part of the first semiconductor film 20 and the lower part of the second semiconductor film 30.

[0021] The first electrode 40 is disposed in contact with the first semiconductor film 20. The arrangement position of the first electrode 40 is not particularly limited, and can be at least one of the front surface, back surface, and side surface of the first semiconductor film 20. In this embodiment, the first electrode 40 is disposed on the side surface of the first semiconductor film 20 in the x direction. Also, the material of the first electrode 40 is not particularly limited. In this embodiment, the material of the first electrode 40 is aluminum (Al).

[0022] The second electrode 50 is disposed in contact with the second semiconductor film 30. The arrangement position of the second electrode 50 is not particularly limited. In this embodiment, the second electrode 50 is disposed on a part of the front surface of the second semiconductor film 30. Also, in this embodiment, the second electrode 50 is disposed near the end in the x direction of the second semiconductor film 30. That is, when viewing the front surface of the second semiconductor film 30 from vertically above (+Z direction), the second electrode 50 is disposed so as to include at least a part of the end 30e of the second semiconductor film 30. Thereby, the entire pn junction J1 is not hidden by the second electrode 50. Also, the material of the second electrode 50 is not particularly limited. In this embodiment, the material of the second electrode 50 is aluminum (Al).

[0023] (Operation of the light receiving element 1 when receiving light) When a voltage is applied such that the second electrode 50 is more positive than the first electrode 40, the pn junction J1 is reverse-biased. A depletion layer DL1 spreads towards the first semiconductor film 20, and a depletion layer DL2 spreads towards the second semiconductor film 30. When eye-safe infrared light IR (e.g., 1550 nm, energy: 0.8 eV) is incident from a light source LS located above (+Z direction) the second semiconductor film 30, the infrared light IR passes through the second semiconductor film 30 and enters the first semiconductor film 20, where it is absorbed by the depletion layer DL1. Electrons and holes are generated by photoexcitation. Due to the internal electric fields of the depletion layers DL1 and DL2, the generated holes flow through the first semiconductor film 20 to the first electrode 40, and the generated electrons flow through the second semiconductor film 30 to the second electrode 50. In this way, in the photodetector 1, a photocurrent flows from the second electrode 50 to the first electrode 40 based on the incident infrared light IR. Based on this photocurrent, the incident infrared light IR can be measured.

[0024] (Manufacturing method for light-receiving element 1) A p-type silicon base substrate 10 is prepared. A first semiconductor film 20 of GeSn is epitaxially grown on the surface of the base substrate 10. Since defects in the GeSn crystal act as acceptors, the first semiconductor film 20 is p-type. A second semiconductor film 30, which is n-type GZO, is epitaxially grown on the surface of the first semiconductor film 20. Subsequently, the first electrode 40 and the second electrode 50 are formed. This completes the photodetector 1 shown in Figure 1.

[0025] (effect) Figure 1(B) shows the distribution of crystal defect density in the first semiconductor film 20 in the thickness direction (z direction). The first semiconductor film 20 is deposited on the upper surface of the base substrate 10 using epitaxial technology. Therefore, due to lattice mismatch between silicon, the material of the base substrate 10, and GeSn, the material of the first semiconductor film 20, a large number of lattice defects are formed on the first semiconductor film 20 side of the junction region between the base substrate 10 and the first semiconductor film 20. The defect density in the first semiconductor film 20 is highest at the position in contact with the base substrate 10 and decreases as it moves away from the base substrate 10. When sufficiently far from the base substrate 10, the defect density in the first semiconductor film 20 is approximately constant. In germanium-containing semiconductor crystals such as GeSn, lattice defects can act as acceptors even without the addition of impurities. Therefore, the p-type carrier concentration is distributed in a similar distribution to the defect density distribution shown in Figure 1(B). In other words, in the portion of the first semiconductor film 20 in contact with the base substrate 10, the p-type carrier concentration increases due to an increase in acceptor concentration caused by lattice defects. As shown in Figure 1(B), the p-type carrier concentration decreases as it moves away from the base substrate 10, and the p-type carrier concentration becomes sufficiently low in the upper part of the first semiconductor film 20.

[0026] In this embodiment, the photodetector 1 has a pn junction J1 formed on top of the first semiconductor film 20, where the defect density is sufficiently reduced. This allows the depletion layer DL1 to be formed in a region where the p-type carrier concentration due to crystal defects is low, thus extending the depletion layer DL1 further towards the first semiconductor film 20. The first semiconductor film 20 is a semiconductor that absorbs infrared light and functions as a photodetector. By extending the depletion layer DL1 within the photodetector, the effective light-receiving area is enlarged, allowing for highly efficient collection of charges excited by light. This makes it possible to improve the light-receiving sensitivity of the photodetector 1.

[0027] In the photodetector 1 of this embodiment, infrared light can be incident on the first semiconductor film 20, which is a photodetector, through a second semiconductor film 30 that is transparent to infrared light. Since the attenuation of infrared light by the second semiconductor film 30 can be prevented, it is possible to improve the photodetector sensitivity. [Examples]

[0028] Figure 2(A) shows a schematic cross-sectional view of the photodetector 201 of Example 2. The contents of the base substrate 210, first semiconductor film 220, second semiconductor film 230, first electrode 240, and second electrode 250 of the photodetector 201 are the same as those of the base substrate 10, first semiconductor film 20, second semiconductor film 30, first electrode 40, and second electrode 50 of Example 1 described above, so a detailed explanation is omitted.

[0029] The base substrate 10 is a p-type silicon substrate. The acceptor concentration is 1 × 10⁻⁶. 15 cm -3 The above is complete. A first semiconductor film 220 is disposed on the surface of the base substrate 10. The first semiconductor film 220 is p-type GeSn. Multiple second semiconductor films 230 are disposed on a portion of the surface of the first semiconductor film 220. The second semiconductor films 230 are n-type GZO.

[0030] The acceptor concentration of the first semiconductor film 220 is preferably lower than the donor concentration of the second semiconductor film 230. This makes it possible to extend the depletion layer DL1 of the first semiconductor film 220 more than the depletion layer DL2 of the second semiconductor film 230. In this embodiment, the acceptor concentration of the first semiconductor film 220 is set to 1 × 10⁻¹⁶. 18 cm -3 The donor concentration of the second semiconductor film 230 is set to 1 × 10⁻⁶. 18 cm -3 That concludes my explanation.

[0031] The second electrode 250 is positioned to cover the entire surface of the second semiconductor film 230. The second electrode 250 is made of a material that transmits infrared light. In this embodiment, the second electrode 250 is made of GZO. It is preferable that the thickness Tb of the second electrode 250 is thinner than the thickness Ta of the second semiconductor film 230. The reason is as follows: When using a transparent oxide semiconductor such as GZO as the material for the second electrode 250, it is necessary to increase the impurity concentration. However, the higher the impurity concentration, the easier it becomes to absorb infrared light. Therefore, by making the second electrode 250 a thin film, infrared light can be more easily transmitted through the second electrode 250.

[0032] The first electrode 240 is positioned in contact with the surface 220s of the first semiconductor film 220 where the second semiconductor film 230 is not located. The material of the first electrode 240 is not particularly limited, but may be aluminum, for example. An insulating portion 260 is positioned between the x-direction side surface of the first electrode 240 and the x-direction side surfaces of the second semiconductor film 230 and the second electrode 250. That is, the insulating portion 260 is positioned in contact with the first electrode 240 and the second electrode 250. Short circuits between the first electrode 240 and the second semiconductor film 230 and the second electrode 250 can be prevented by the insulating portion 260. The material of the insulating portion 260 is not particularly limited. In this embodiment, the insulating portion 260 is silicon oxide (SiO2).

[0033] Multiple second semiconductor films 230 are arranged on the surface 220s of the first semiconductor film 220. This forms multiple pn junctions J1. In each of the multiple pn junctions J1, a depletion layer DL1 extends toward the first semiconductor film 20 side, and a depletion layer DL2 extends toward the second semiconductor film 30 side. The depletion layer DL1 extends so as to protrude by a distance DD from the x-direction edge 230e of the second semiconductor film 230. The distance DD is a value determined by the acceptor concentration of the first semiconductor film 220 and the magnitude of the reverse bias voltage applied between the first electrode 240 and the second electrode 250. The width Wx in the x-direction of the insulating portion 260 is set to be greater than the distance DD. As a result, the depletion layer DL1 does not directly connect to the first electrode 240.

[0034] When the photodetector 201 is in use, the light source LS is positioned above the second electrode 250 (in the +Z direction). That is, the second semiconductor film 230 faces the light source LS. Infrared light IR passes through the second electrode 250 and the second semiconductor film 230 and is absorbed in the depletion layer DL1.

[0035] The planar structure of the photodetector 201 may vary. The first electrode 240 and the insulating portion 260 may be arranged in a grid pattern. Alternatively, for example, the second semiconductor film 230 and the second electrode 250 may be circular, with the first electrode 240 and the insulating portion 260 surrounding them.

[0036] (Manufacturing method for the light-receiving element 201) A first semiconductor film 220 of GeSn is epitaxially grown on the surface of a p-type silicon base substrate 210. A second semiconductor film 230, which is n-type GZO, is epitaxially grown on the surface 220s of the first semiconductor film 220. A second electrode 250 is deposited on the surface of the second semiconductor film 230. A mask (not shown) is formed with openings in the regions corresponding to the first electrode 240 and the insulating portion 260, and anisotropic etching is performed. As a result, as shown in Figure 3, multiple openings OP are formed on the bottom surface, in which the surface 220s of the first semiconductor film 220 is exposed. The second semiconductor film 230 and the second electrode 250 are then divided into multiple regions.

[0037] An insulating portion 260 is formed to cover the x-direction sides of the second semiconductor film 230 and the second electrode 250. For example, after depositing an insulating film over the entire surface, the insulating portion 260 can be formed by removing the insulating film on the surface of the second electrode 250 and the surface 220s of the first semiconductor film 220 by anisotropic etching. Subsequently, the first electrode 240 is formed so as to be in contact with the surface 220s and the insulating portion 260. For example, after depositing a metal film over the entire surface, the first electrode 240 can be formed by removing the metal film on the surface of the second electrode 250 and the upper surface of the insulating portion 260 by anisotropic etching. This completes the photodetector 201 shown in Figure 2.

[0038] (effect) The first electrode 240 can be positioned to contact the surface 220s of the first semiconductor film 220. Compared to the case where the first electrode 240 is in contact with the x-side surface of the first semiconductor film 220, this allows for a larger contact area and greater flexibility in the layout of the first electrode 240.

[0039] The second electrode 250 can be placed across the entire surface of the second semiconductor film 230. Since the distance between the second electrode 250 and the depletion layer DL2 can be made uniform in the planar direction, it becomes possible to pass a photocurrent uniformly in the planar direction.

[0040] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. Furthermore, the technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness.

[0041] (modified version) The arrangement of the first and second electrodes can vary. For example, as shown in the photodetector 301 of Figure 4, the second electrode 350 may be arranged so as to surround the outer periphery of the surface of the second semiconductor film 330. Alternatively, the first electrode 340 may be arranged so as to surround the second electrode 350. The first electrode 340 is in contact with the second electrode 350 and the second semiconductor film 330 via the insulating portion 360, and is also in contact with the surface 320s of the first semiconductor film 320.

[0042] In Example 1 (Figure 1), the silicon base substrate 10 can also be used as an electrode in contact with the first semiconductor film 20. In this case, the first electrode 40 can be omitted. In Example 2 (Figure 2), the silicon base substrate 210 can also be used as an electrode in contact with the first semiconductor film 220. In this case, the first electrode 240 can be omitted.

[0043] The conductivity type relationships described herein are examples only. For example, in Example 1, the base substrate 10 and the first semiconductor film 20 may be n-type, and the second semiconductor film 30 may be p-type. Also, for example, in Example 2, the base substrate 210 and the first semiconductor film 220 may be n-type, and the second semiconductor film 230 may be p-type.

[0044] The deposition method for the first semiconductor films 20 and 220 and the second semiconductor films 30 and 230 is not limited to epitaxial growth. For example, it may be a method of single-crystallizing the amorphous layer to match the crystal structure of the underlying substrate by annealing.

[0045] The following are embodiments of this technology. [Aspect 1] Base board and A first semiconductor film of a first conductivity type disposed on the base substrate, A second semiconductor film of a second conductivity type is disposed on the first semiconductor film, A first electrode in contact with the aforementioned first semiconductor film, The second electrode in contact with the aforementioned second semiconductor film, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The aforementioned first semiconductor film is a semiconductor that absorbs infrared light, The second semiconductor film is a semiconductor that transmits infrared light. Light-receiving element. [Aspect 2] A base substrate of a first-type conductive semiconductor, A first semiconductor film of a first conductivity type disposed on the base substrate, A second semiconductor film of a second conductivity type is disposed on the first semiconductor film, A first electrode in contact with the aforementioned first semiconductor film, The second electrode in contact with the aforementioned second semiconductor film, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The aforementioned first semiconductor film is a semiconductor that absorbs infrared light, The second semiconductor film is a semiconductor that transmits infrared light. Light-receiving element. [Aspect 3] A base substrate for a p-type semiconductor, A p-type first semiconductor film disposed on the base substrate, An n-type second semiconductor film is placed on the preceding first semiconductor film, A first electrode in contact with the aforementioned first semiconductor film, The second electrode in contact with the aforementioned second semiconductor film, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The aforementioned first semiconductor film is a semiconductor that absorbs infrared light, The second semiconductor film is a semiconductor that transmits infrared light. Light-receiving element. [Aspect 4] A base substrate for a p-type semiconductor, A p-type first semiconductor film disposed on the base substrate, An n-type second semiconductor film is disposed on a part of the surface of the first semiconductor film, A first electrode is disposed in contact with the surface of the first semiconductor film where the second semiconductor film is not disposed, The second electrode in contact with the aforementioned second semiconductor film, An insulating portion is positioned in contact with the first electrode and the second electrode, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The aforementioned first semiconductor film is a semiconductor that absorbs infrared light, The second semiconductor film is a semiconductor that transmits infrared light. Light-receiving element. [Aspect 5] The photodetector according to any one of embodiments 1 to 4, wherein the first semiconductor film is a semiconductor containing Ge. [Aspect 6] The photodetector according to any one of embodiments 1 to 5, wherein the second electrode is disposed on at least a portion of the surface of the second semiconductor film and is made of a material that transmits infrared light. [Aspect 7] The first semiconductor film is GeSn, The photodetector according to any one of embodiments 1 to 6, wherein the second semiconductor film is a transparent oxide semiconductor. [Aspect 8] The second semiconductor film is located on a portion of the surface of the first semiconductor film. The first electrode is positioned in contact with the surface of the first semiconductor film where the second semiconductor film is not located. The second electrode is located on at least a portion of the surface of the second semiconductor film. The second electrode is positioned such that, when the surface of the second semiconductor film is viewed from vertically above, it includes at least a portion of the edge of the second semiconductor film. The light-receiving element according to any one of embodiments 1 to 7, further comprising an insulating portion disposed in contact with the first electrode and the second electrode. [Explanation of Symbols]

[0046] 1: Photodetector 10: Base substrate 20: First semiconductor film 30: Second semiconductor film 40: First electrode 50: Second electrode DL1, DL2: Depletion layer J1: pn junction

Claims

1. Base board and A first semiconductor film of a first conductivity type disposed on the base substrate, A second semiconductor film of a second conductivity type is disposed on the first semiconductor film, A first electrode in contact with the first semiconductor film, The second electrode in contact with the second semiconductor film, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared rays, and is GeSn. The second semiconductor film is a semiconductor that transmits infrared light and is a transparent oxide semiconductor. Light-receiving element.

2. A base substrate of a first-conductivity semiconductor, A first semiconductor film of a first conductivity type disposed on the base substrate, A second semiconductor film of a second conductivity type is disposed on the first semiconductor film, A first electrode in contact with the first semiconductor film, The second electrode in contact with the second semiconductor film, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared rays, and is GeSn. The second semiconductor film is a semiconductor that transmits infrared light and is a transparent oxide semiconductor. Light-receiving element.

3. A base substrate for a p-type semiconductor, A p-type first semiconductor film disposed on the base substrate, An n-type second semiconductor film disposed on the first semiconductor film, A first electrode in contact with the first semiconductor film, The second electrode in contact with the second semiconductor film, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared rays, and is GeSn. The second semiconductor film is a semiconductor that transmits infrared light and is a transparent oxide semiconductor. Light-receiving element.

4. A base substrate for a p-type semiconductor, A p-type first semiconductor film disposed on the base substrate, An n-type second semiconductor film is disposed on a part of the surface of the first semiconductor film, A first electrode is disposed in contact with the surface of the first semiconductor film where the second semiconductor film is not disposed, The second electrode in contact with the second semiconductor film, An insulating portion is positioned in contact with the first electrode and the second electrode, A light-receiving element equipped with, The second semiconductor film has a larger band gap than the first semiconductor film. The first semiconductor film is a semiconductor that absorbs infrared rays, and is GeSn. The second semiconductor film is a semiconductor that transmits infrared light and is a transparent oxide semiconductor. Light-receiving element.

5. The photodetector according to any one of claims 1 to 4, wherein the second electrode is disposed on at least a portion of the surface of the second semiconductor film and is made of a material that transmits infrared light.

6. The second semiconductor film is arranged on a part of the surface of the first semiconductor film, The first electrode is positioned in contact with the surface of the first semiconductor film where the second semiconductor film is not located. The second electrode is located on at least a portion of the surface of the second semiconductor film. The second electrode is positioned such that, when the surface of the second semiconductor film is viewed from vertically above, it includes at least a portion of the edge of the second semiconductor film. The light-receiving element according to any one of claims 1 to 4, further comprising an insulating portion disposed in contact with the first electrode and the second electrode.

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