Photodetector

Abstract

To provide a photodetector capable of improving detection sensitivity while suppressing dark current.SOLUTION: A photodetector 1A comprises: a first conductivity type semiconductor layer 2; a semiconductor light absorption layer 3 provided on the first conductivity type semiconductor layer 2; a scatterer 4 provided with a width W equal to or less than the wavelength of incident light I so as to be in contact with the semiconductor light absorption layer 3, and forming a localized ununiform electric field inside the semiconductor light absorption layer 3 by scattering the incident light I; a second conductivity type semiconductor layer 5 provided on the semiconductor light absorption layer 3 separated from the scatterer 4; and an extraction electrode 6 provided on the second conductivity type semiconductor layer 5 separated from the scatterer 4, and extracting a photocurrent generated in the semiconductor light absorption layer 3 by the formation of the localized ununiform electric field.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a photodetector.

Background Art

[0002] In recent years, the development of laser sensing technology used in vehicle automatic driving functions and collision prevention functions has become remarkable, and the development of an inexpensive and high-performance photodetector in the infrared region has been demanded. For example, in the short-wavelength infrared (SWIR) band of 1.3 μm or more in wavelength, semiconductor light-receiving elements using InGaAs as a substrate are mainstream, but high-performance array-type photodetectors using such a substrate have problems in terms of cost.

[0003] Under such circumstances, as a photodetector that does not depend on InGaAs, a photodetector that utilizes a localized non-uniform electric field inside a semiconductor light absorption layer has been developed. In this type of photodetector, generally, a semiconductor material with indirect transition is used, and a localized non-uniform electric field is generated inside the semiconductor light absorption layer in response to light incidence. One of the effects of the localized non-uniform electric field is that, due to the uncertainty principle, a large wave number is given to electrons inside the semiconductor. Therefore, even in a semiconductor material with indirect transition, direct optical transition becomes possible, and sufficient light absorption is ensured.

[0004] Examples of such a photodetector include the light-receiving element described in Patent Document 1. In this conventional light-receiving element, a first-conductivity-type semiconductor layer, an undoped semiconductor light absorption layer, a second-conductivity-type semiconductor layer, and a conductive layer are provided in this order on a substrate. The laminate of the conductive layer, the second-conductivity-type semiconductor layer, and the undoped semiconductor light absorption layer has a plurality of openings arranged periodically. This opening has a width that is equal to or less than the wavelength of the incident light and is provided so as to penetrate the conductive layer and the second-conductivity-type semiconductor layer and reach the undoped semiconductor light absorption layer.

[0005] Further, for example, the light-receiving element described in Patent Document 2 has a semiconductor layer and a pair of metal electrodes that are disposed on the surface of the semiconductor layer at a predetermined interval d and form an MSM junction. The interval between the pair of metal electrodes satisfies the relationship of λ > d when the wavelength of the incident light is λ. At least one of the pair of metal electrodes forms a Schottky junction with the semiconductor layer and is embedded in the semiconductor layer to a position where the depth is smaller than λ / (2n) when the refractive index of the semiconductor layer is n.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In order to improve the detection sensitivity in the photodetector as described above, it is necessary to sufficiently secure the wave number component of the localized non-uniform electric field in the semiconductor light absorption layer. The effect of the localized non-uniform electric field rapidly attenuates as the distance between the generation position of the localized non-uniform electric field and the depletion layer position in the semiconductor light absorption layer increases. In the light-receiving element described in Patent Document 1, the generation position of the localized non-uniform electric field is near the interface between the conductive layer and the second conductivity type semiconductor layer, but the generation position is separated from the non-doped type semiconductor light absorption layer by the thickness of the second conductivity type semiconductor layer. Therefore, there is room for further improvement from the viewpoint of improving the detection sensitivity.

[0008] In the light-receiving element described in Patent Document 2, the detection sensitivity is improved by embedding the metal electrode in the semiconductor layer. However, since the semiconductor layer that becomes the generation position of the localized non-uniform electric field is integrated with the extraction electrode of the photocurrent, there is a problem that the dark current caused by the Schottky junction becomes relatively large. Therefore, the light-receiving element described in Patent Document 2 has a problem that it is difficult to improve the signal-to-noise ratio.

[0009] The present disclosure has been made to solve the above problems, and an object thereof is to provide a photodetector capable of improving detection sensitivity while suppressing dark current.

Means for Solving the Problems

[0010] The photodetector according to one aspect of the present disclosure includes a first conductivity type semiconductor layer, a semiconductor optical absorption layer provided on the first conductivity type semiconductor layer, and a scatterer provided in a width equal to or less than the wavelength of incident light so as to be in contact with the semiconductor optical absorption layer, the scatterer forming a localized non-uniform electric field inside the semiconductor optical absorption layer by scattering the incident light, a second conductivity type semiconductor layer provided on the semiconductor optical absorption layer while being separated from the scatterer, and a extraction electrode provided on the second conductivity type semiconductor layer while being separated from the scatterer, the extraction electrode extracting a photocurrent generated in the semiconductor optical absorption layer due to the formation of the localized non-uniform electric field.

[0011] In this photodetector, the scatterer that forms a localized non-uniform electric field inside the semiconductor optical absorption layer by scattering the incident light is provided in a width equal to or less than the wavelength of the incident light so as to be in contact with the semiconductor optical absorption layer. Thereby, it becomes possible to make the generation position of the localized non-uniform electric field coincide with or be close to the depletion layer position in the semiconductor optical absorption layer, and the effect of the localized non-uniform electric field in the semiconductor optical absorption layer can be sufficiently exerted, so that the detection sensitivity can be improved. Further, in this photodetector, the extraction electrode that extracts the photocurrent generated in the semiconductor optical absorption layer due to the formation of the localized non-uniform electric field is provided separated from the scatterer. With such a configuration, the generation of dark current due to the Schottky junction can be suppressed as compared with the case where the semiconductor optical absorption layer and the extraction electrode are in contact with each other, or the case where the scatterer itself serves as the extraction electrode.

[0012] The scatterer may be a metal nanostructure that generates surface plasmon resonance in the vicinity of the interface between the scatterer and the semiconductor optical absorption layer. In this case, the scatterer can be formed at a desired position with high reproducibility by nanopatterning. Therefore, the manufacturing yield of the photodetector can be increased.

[0013] In the second conductivity type semiconductor layer, a concave portion is provided that penetrates the second conductivity type semiconductor layer and cuts out a part of the semiconductor light absorption layer, and the scatterer may be disposed on the bottom surface of the concave portion. According to this configuration, the scatterer and the junction interface between the first conductivity type semiconductor layer and the semiconductor light absorption layer can be brought closer according to the depth of the concave portion. Therefore, the path of the photocurrent generated in the semiconductor light absorption layer is shortened, and high-speed response of light detection can be realized.

[0014] In the second conductivity type semiconductor layer, a concave portion is provided that penetrates the second conductivity type semiconductor layer and cuts out a part of the semiconductor light absorption layer, and the scatterer may be disposed over the bottom surface and the inner wall surface of the concave portion. In this case, since lift-off using a resist for nanopatterning is not required for forming the scatterer, the manufacturability of the photodetector can be improved.

[0015] The semiconductor light absorption layer is composed of a first layer with a p-type conductivity type, a second layer with an i-type conductivity type, and a third layer with an n-type conductivity type. The concave portion is provided with a depth that cuts out a part of the second layer, and the scatterer may be disposed on the bottom surface of the concave portion so as to be buried in the second layer. According to this configuration, since the scatterer is buried in the second layer with an i-type conductivity type that becomes the depletion layer position, the path of the photocurrent generated in the semiconductor light absorption layer is shortened, and high-speed response of light detection can be realized. In addition, it becomes possible to match the depletion layer position with a region where the electric field changes steeply due to the localized non-uniform electric field, and efficient photoelectric conversion of incident light can be caused.

[0016] The width of the concave portion may be equal to or less than the wavelength of the incident light over the entire depth direction. In this case, it becomes easy to match the depletion layer position with a region where the electric field changes steeply due to the localized non-uniform electric field, and the efficiency of photoelectric conversion of the incident light can be further increased.

[0017] Of the concave portion, the width of the portion penetrating the second conductivity type semiconductor layer may be larger than the width of the portion cutting out a part of the semiconductor light absorption layer. In this case, the loss of the incident light by the second conductivity type semiconductor layer can be reduced. This configuration is suitable for a configuration in which light is incident from the second conductivity type semiconductor layer side.

[0018] An insulating layer formed of a material having a refractive index smaller than that of the semiconductor light absorption layer may be provided in the recess. In this case, the insulating layer can protect the scatterer and prevent leakage from the scatterer. Further, since the refractive index of the insulating layer is smaller than the refractive index of the semiconductor light absorption layer, a local non-uniform electric field can be concentrated in the semiconductor light absorption layer having a relatively high refractive index. Therefore, further improvement in detection sensitivity can be achieved.

[0019] A plurality of scatterers may be provided at regular intervals in the in-plane direction of the interface between the scatterer and the semiconductor light absorption layer. In this case, the light reception region (the area of the scatterer) of the incident light is expanded, thereby improving the detection sensitivity.

[0020] The photodetector is a back-illuminated photodetector that incident light from the first conductivity type semiconductor layer side, and a reflective film that reflects the component of the incident light incident from the back surface and transmitted through the scatterer toward the semiconductor absorption layer side may be provided on the second conductivity type semiconductor layer. In this case, the component transmitted through the scatterer is reflected by the reflective film and travels again toward the semiconductor light absorption layer, so that the amount of light absorption in the semiconductor light absorption layer can be improved.

Advantages of the Invention

[0021] According to the present disclosure, the detection sensitivity can be improved while suppressing the dark current.

Brief Description of the Drawings

[0022]

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[0023] Hereinafter, with reference to the drawings, a preferred embodiment of the photodetector according to one aspect of the present disclosure will be described in detail.

[0024] In each of the embodiments and the drawings of the photodetector shown below, one structural unit of the incident region of the incident light to be detected is shown as the main part. However, in an actual photodetector, these structural units are arrayed at a predetermined pitch. [First Embodiment of Photodetector]

[0025] FIG. 1(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the first embodiment of the present disclosure, and FIG. 1(b) is a plan view thereof. As shown in the figure, the photodetector 1A according to the first embodiment includes a first conductivity type semiconductor layer 2, a semiconductor light absorption layer 3, a scatterer 4, a second conductivity type semiconductor layer 5, and extraction electrodes 6A and 6B. In this embodiment, for convenience, the side of the first conductivity type semiconductor layer 2 is defined as the back side of the photodetector 1A, and the side of the second conductivity type semiconductor layer 5 is defined as the front side of the photodetector 1A. In the example of FIG. 1(a), the photodetector 1A is a surface incident type detector in which incident light I is incident from the front side. However, the photodetector of the present disclosure may be either a surface incident type detector or a back incident type detector.

[0026] In the photodetector 1A, when light having a wavelength longer than the absorption edge wavelength of the semiconductor (the wavelength of light having energy exceeding the bandgap) is incident as incident light I, surface plasmons are excited by the incident light I. Then, a localized non-uniform electric field is generated by the resonance of the surface plasmons. Therefore, in the photodetector 1A, by utilizing the effect of the localized non-uniform electric field, direct optical transitions in the semiconductor become possible, and sufficient light absorption in the semiconductor can be caused. In the photodetector 1A, the light absorption generated in the semiconductor is taken out as a photocurrent to the outside, thereby enabling detection of light having a wavelength longer than the absorption edge wavelength of the semiconductor. Here, assuming that the wavelength of the incident light I to be detected is around 1200 nm, the dimensions and the like of each component of the photodetector 1 will be exemplified.

[0027] The first conductivity type semiconductor layer 2 is made of, for example, n-type Si with a high carrier concentration and is composed of a low-resistance semiconductor (n+) with a high carrier concentration. The first conductivity type semiconductor layer 2 has a rectangular shape in plan view and has a first surface 2a and a second surface 2b opposite to the first surface 2a. The first surface 2a is a surface facing the back side of the photodetector 1A, and the second surface 2b is a surface facing the front side of the photodetector 1A. The thickness of the first conductivity type semiconductor layer 2 is, for example, 1 μm or more and 50 μm or less.

[0028] The semiconductor optical absorption layer 3 is made of, for example, p-type Si with a low carrier concentration and is composed of a high-resistance semiconductor (p-) with a low carrier concentration. The semiconductor optical absorption layer 3 has a rectangular shape in plan view and has a first surface 3a and a second surface 3b opposite to the first surface 3a. The first surface 3a is a surface facing the back side of the photodetector 1A, and the second surface 3b is a surface facing the front side of the photodetector 1A. The semiconductor optical absorption layer 3 is provided so as to cover the entire surface of the second surface 2b of the first conductivity type semiconductor layer 2. The thickness of the semiconductor optical absorption layer 3 is determined according to the carrier concentrations of the first conductivity type semiconductor layer 2 and the semiconductor optical absorption layer 3, but is, for example, 50 nm or more and 100 μm or less. At the interface between the semiconductor optical absorption layer 3 and the first conductivity type semiconductor layer 2, a pn junction of the semiconductor is formed.

[0029] The scatterer 4 is a structure that forms a localized non-uniform electric field inside the semiconductor optical absorption layer 3 by scattering the incident light I. The scatterer 4 is composed of a material having a refractive index different from at least a part of the surrounding elements. Specifically, the scatterer 4 is composed of a material having a refractive index different from at least one of the semiconductor optical absorption layer 3 and air. Here, the scatterer 4 is composed of a metal nanostructure 7 that generates surface plasmon resonance near the interface between the scatterer 4 and the semiconductor optical absorption layer 3 by the incidence of the incident light I. Examples of the metal material constituting the metal nanostructure 7 include gold (Au), silver (Ag), copper (Cu), aluminum (Al), and the like. The metal nanostructure 7 may be composed of a compound material containing these metals.

[0030] In the examples of FIGS. 1(a) and 1(b), the metal nanostructure 7 is provided with a width W equal to or less than the wavelength of the incident light I so as to be in contact with the second surface 3b of the semiconductor optical absorption layer 3. The width W1 of the metal nanostructure 7 is, for example, 20 nm or more and 500 nm or less. The thickness T1 of the metal nanostructure 7 is smaller than the thickness of the semiconductor optical absorption layer 3, and is, for example, 10 nm or more and 500 nm or less. The metal nanostructure 7 has a rectangular shape in plan view and extends linearly in one direction in the in-plane direction of the second surface 3b so as to reach from one side to the other side of the second surface 3b of the semiconductor optical absorption layer 3. When the wavelength of the incident light I is in the vicinity of 1200 nm, for example, when the width W1 of the metal nanostructure 7 is 100 nm and the thickness T1 is 100 nm, surface plasmon resonance caused by the incident light I can be suitably generated near the interface between the scatterer 4 and the semiconductor optical absorption layer 3.

[0031] The second conductivity type semiconductor layer 5 is made of, for example, p-type Si with a high carrier concentration and is composed of a low-resistance semiconductor (p+) with a high carrier concentration. The second conductivity type semiconductor layer 5 has a rectangular shape in plan view and has a first surface 5a and a second surface 5b opposite to the first surface 5a. The thickness of the second conductivity type semiconductor layer 5 is larger than the thickness T1 of the metal nanostructure 7, and is, for example, 100 nm or more and 1000 nm or less. A concave portion 8 is provided in the central portion of the second conductivity type semiconductor layer 5. The depth D of the concave portion 8 is equal to the thickness of the second conductivity type semiconductor layer 5, and the second surface 3b of the semiconductor light absorption layer 3 and the metal nanostructure 7 on the second surface 3b are exposed on the bottom surface 8a of the concave portion 8.

[0032] In plan view, the concave portion 8 extends linearly in one direction in the in-plane direction of the second surface 3b so as to reach from one side to the other side of the second surface 3b of the semiconductor light absorption layer 3. Further, the width W2 of the concave portion 8 is sufficiently larger than the width W1 of the metal nanostructure 7. Thereby, in plan view, the second conductivity type semiconductor layer 5 sandwiches the metal nanostructure 7 in the width direction and is disposed at a distance from the metal nanostructure 7. The separation width between the second conductivity type semiconductor layer 5 and the metal nanostructure 7 is not particularly limited, but is, for example, larger than the width W1 of the metal nanostructure 7.

[0033] The extraction electrodes 6A and 6B are electrodes for extracting the photocurrent generated in the semiconductor light absorption layer 3 by the formation of a localized non-uniform electric field. The extraction electrode 6A is an electrode layer that functions as the anode of the photodetector 1A. The extraction electrode 6A is provided on the first surface 2a side of the first conductivity type semiconductor layer 2. The extraction electrode 6A has a rectangular shape in plan view, and extends linearly in one direction in the in-plane direction of the first surface 2a so as to reach from one side to the other side of the first surface 2a of the first conductivity type semiconductor layer 2, for example, at a position overlapping the second conductivity type semiconductor layer 5. The extraction electrode 6A is formed of a metal such as aluminum (Al), titanium (Ti), indium (In), etc. The extraction electrode 6A may be composed of a compound material containing these metals. The extraction electrode 6A is not limited to a single layer and may be composed of a plurality of layers.

[0034] The extraction electrode 6B is an electrode layer that functions as the cathode of the photodetector 1A. The extraction electrode 6B is provided on the second surface 5b side of the second-conductivity-type semiconductor layer 5. As described above, the second-conductivity-type semiconductor layer 5 is disposed sufficiently apart from the metal nanostructure 7. Therefore, the extraction electrode 6B on the second-conductivity-type semiconductor layer 5 is also disposed sufficiently apart from the metal nanostructure 7. The extraction electrode 6B, similar to the extraction electrode 6A, has a rectangular shape in plan view and extends linearly in one direction in the in-plane direction of the second surface 5b so as to reach from one side to the other side of the second surface 5b of the second-conductivity-type semiconductor layer 5. The extraction electrode 6B is formed of a metal such as gold (Au), aluminum (Al), platinum (Pt), etc. The extraction electrode 6B may be composed of a compound material containing these metals. The extraction electrode 6B is not limited to a single layer and may be composed of a plurality of layers.

[0035] As described above, in the photodetector 1A, the scatterer 4 that forms a localized non-uniform electric field inside the semiconductor optical absorption layer 3 by scattering the incident light I is provided with a width equal to or less than the wavelength of the incident light I so as to be in contact with the semiconductor optical absorption layer 3. Thereby, it becomes possible to make the generation position of the localized non-uniform electric field coincide with or be close to the depletion layer position in the semiconductor optical absorption layer, and the effect of the localized non-uniform electric field in the semiconductor optical absorption layer 3 can be sufficiently exerted. Therefore, the detection sensitivity can be improved.

[0036] Also, in the photodetector 1A, the extraction electrodes 6A and 6B that extract the photocurrent generated in the semiconductor optical absorption layer 3 due to the formation of the localized non-uniform electric field are provided apart from the scatterer 4. With such a configuration, the scatterer 4 does not contribute to the extraction of the photocurrent and only has the function of forming the localized non-uniform electric field. Therefore, compared with the case where the semiconductor optical absorption layer 3 is in contact with the extraction electrodes 6A and 6B, or the case where the scatterer 4 itself serves as the extraction electrode, the generation of dark current due to the Schottky junction can be suppressed.

[0037] In the photodetector 1A, the scatterer 4 is constituted by a metal nanostructure 7 that generates surface plasmon resonance near the interface between the scatterer 4 and the semiconductor optical absorption layer 3. When the scatterer 4 is constituted by the metal nanostructure 7, the scatterer 4 can be formed at a desired position with high reproducibility by nanopatterning. Therefore, the manufacturing yield of the photodetector 1A can be increased. [Second Embodiment of Photodetector]

[0038] FIG. 2(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the second embodiment of the present disclosure, and FIG. 2(b) is a plan view thereof. As shown in the figure, the photodetector 1B according to the second embodiment is different from the first embodiment in that the recess 8 of the second conductivity type semiconductor layer 5 penetrates the second conductivity type semiconductor layer 5 and further cuts out a part of the semiconductor optical absorption layer 3.

[0039] The metal nanostructure 7 is disposed on the bottom surface 8a of the recess 8 and is located on a surface that is one step lower than the surface on which the second conductivity type semiconductor layer 5 is provided in the semiconductor optical absorption layer 3. In the example of FIG. 2(a), in the photodetector 1B, the depth Da of the cutout portion of the semiconductor optical absorption layer 3 due to the recess 8 is equal to or less than the thickness T1 of the metal nanostructure 7 that is the scatterer 4. Therefore, in the photodetector 1B, the metal nanostructure 7 disposed on the bottom surface 8a of the recess 8 is in a state of slightly protruding toward the second conductivity type semiconductor layer 5 side from the surface on which the second conductivity type semiconductor layer 5 is provided. The depth Da of the cutout portion of the semiconductor optical absorption layer 3 due to the recess 8 may be larger than the thickness T1 of the metal nanostructure 7 that is the scatterer 4.

[0040] Also in such a photodetector 1B, since the scatterer 4 is provided with a width equal to or less than the wavelength of the incident light I so as to be in contact with the semiconductor optical absorption layer 3, it is possible to make the generation position of the localized non-uniform electric field coincide with or be close to the depletion layer position in the semiconductor optical absorption layer. Therefore, the effect of the localized non-uniform electric field in the semiconductor optical absorption layer 3 can be sufficiently exerted, and the detection sensitivity can be improved. Further, also in the photodetector 1B, since the extraction electrodes 6A and 6B are provided at a distance from the scatterer 4, the generation of dark current due to the Schottky junction can be suppressed.

[0041] In the photodetector 1B, a recess 8 that penetrates the second-conductivity-type semiconductor layer 5 and cuts out a part of the semiconductor optical absorption layer 3 is provided in the second-conductivity-type semiconductor layer 5, and the scatterer 4 is disposed on the bottom surface 8a of the recess 8. According to this configuration, the scatterer 4 and the pn junction interface between the first-conductivity-type semiconductor layer 2, the semiconductor optical absorption layer 3 can be brought closer according to the depth of the recess 8. Therefore, the path of the photocurrent generated in the semiconductor optical absorption layer 3 is shortened, and high-speed response of photodetection can be realized. [Third Embodiment of Photodetector]

[0042] FIG. 3(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the third embodiment of the present disclosure, and FIG. 3(b) is a plan view thereof. As shown in the figure, the photodetector 1C according to the third embodiment is further different from the second embodiment in that the width W2 of the recess 8 is equal to or less than the wavelength of the incident light I over the entire depth direction.

[0043] In the photodetector 1C, the width W1 of the metal nanostructure 7 is equal to or less than the wavelength of the incident light I, and the width W2 of the recess 8 coincides with the width W1 of the metal nanostructure 7. In the photodetector 1C, the depth Da of the cutout portion of the semiconductor optical absorption layer 3 by the recess 8 is larger than the thickness T1 of the metal nanostructure 7 serving as the scatterer 4. Therefore, in the photodetector 1C, the metal nanostructure 7 disposed on the bottom surface 8a of the recess 8 does not protrude toward the second-conductivity-type semiconductor layer 5 side from the surface on which the second-conductivity-type semiconductor layer 5 is provided, and is in a state of being buried in the semiconductor optical absorption layer 3.

[0044] Also in such a photodetector 1C, since the scatterer 4 is provided with a width equal to or less than the wavelength of the incident light I so as to be in contact with the semiconductor optical absorption layer 3, it is possible to make the generation position of the localized non-uniform electric field coincide with or be close to the depletion layer position in the semiconductor optical absorption layer. Therefore, the effect of the localized non-uniform electric field in the semiconductor optical absorption layer 3 can be sufficiently exerted, and the detection sensitivity can be improved. Also in the photodetector 1C, since the extraction electrodes 6A and 6B are provided at a distance from the scatterer 4, the generation of dark current due to the Schottky junction can be suppressed.

[0045] In the photodetector 1C, by adjusting the carrier concentrations of the first conductivity type semiconductor layer 2 and the semiconductor optical absorption layer 3, it becomes possible to widen the depletion layer inside the semiconductor optical absorption layer 3. As an example, in the photodetector 1C, the carrier concentration of the first conductivity type semiconductor layer 2 is set to 1×10 19 cm -3 or more, and the carrier concentration of the semiconductor optical absorption layer 3 is set to 1×10 16 cm -3 or less. Then, a depletion layer can be formed over 300 nm or more from the interface between the semiconductor optical absorption layer 3 and the first conductivity type semiconductor layer 2, which is the interface of the pn junction, toward the inner side of the semiconductor optical absorption layer 3. Thereby, it becomes possible to position the depletion layer at a region where the electric field changes steeply due to the localized non-uniform electric field, and the photoelectric conversion of the incident light I can be efficiently caused. [Fourth Embodiment of Photodetector]

[0046] FIG. 4(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the fourth embodiment of the present disclosure, and FIG. 4(b) is a plan view thereof. As shown in the figure, the photodetector 1D according to the fourth embodiment is further different from the third embodiment in that the scatterer 4 is disposed over the bottom surface 8a and the inner wall surface 8b of the recess 8. In the photodetector 1D, the scatterer 4 is constituted by a non-conductive dielectric nanostructure 10 instead of the metal nanostructure 7.

[0047] In the photodetector 1D, the width W2 of the recess 8 is equal to or less than the wavelength of the incident light I over the entire depth direction, while the dielectric nanostructure 10 is disposed over the bottom surface 8a and the inner wall surface 8b of the recess 8. Further, in the photodetector 1D, the dielectric nanostructure 10 projects toward the second surface 5b side of the second-conductive-type semiconductor layer 5 and extends along the opening edge portion 8c of the recess 8. The width W1 of the dielectric nanostructure 10 is larger than the width W2 of the recess 8 but is equal to or less than the wavelength of the incident light I. Even in such a photodetector 1D, the same operational effects as those of the third embodiment are achieved. Further, according to this configuration, since lift-off using a resist for nanopatterning is not required in forming the scatterer 4, the manufacturability of the photodetector 1D can be improved. [Fifth Embodiment of Photodetector]

[0048] FIG. 5(a) is a schematic cross-sectional view showing the configuration of a photodetector according to the fifth embodiment of the present disclosure, and FIG. 5(b) is a plan view thereof. As shown in the figure, the photodetector 1E according to the fifth embodiment further differs in the configuration of the semiconductor light absorption layer 3 from the third embodiment.

[0049] In the photodetector 1E, the width W2 of the recess 8 is equal to or less than the wavelength of the incident light I over the entire depth direction, while the pn junction of the semiconductor is replaced with a pin junction. Specifically, the semiconductor light absorption layer 3 is composed of a first layer 11 made of a high-resistance semiconductor layer of p-type conductivity, a second layer 12 made of a semiconductor layer of i-type conductivity, and a third layer 13 made of a high-resistance semiconductor layer of n-type conductivity. The first layer 11 is located on the first-conductive-type semiconductor layer 2 side, and the third layer 13 is located on the second-conductive-type semiconductor layer 5 side. The second layer 12 is located between the first layer 11 and the third layer 13. The recess 8 is provided with a depth that cuts out a part of the second layer 12, and the scatterer 4 is disposed on the bottom surface 8a of the recess 8 so as to be buried in the second layer 12.

[0050] Even in such a photodetector 1E, the same operational effects as those of the third embodiment are achieved. Further, according to the configuration of the photodetector 1E, since the scatterer 4 is buried in the second layer 12 having an i-type conductivity type that becomes the depletion layer position, the path of the photocurrent generated in the semiconductor optical absorption layer 3 is shortened, and high-speed response of photodetection can be realized. Further, it becomes possible to match the depletion layer position with a region where the electric field changes steeply due to the localized non-uniform electric field, and the photoelectric conversion of the incident light I can be efficiently generated. [Sixth Embodiment of Photodetector]

[0051] FIG. 6(a) is a schematic cross-sectional view showing the configuration of a photodetector according to the sixth embodiment of the present disclosure, and FIG. 6(b) is a plan view thereof. As shown in the figure, the photodetector 1F according to the sixth embodiment is further different in the configuration of the recess 8 from the second embodiment.

[0052] Specifically, in the photodetector 1F, among the recesses 8, the width W2a of the portion penetrating the second conductivity type semiconductor layer 5 is larger than the width W2b of the portion notching a part of the semiconductor optical absorption layer 3. The width W2a of the portion penetrating the second conductivity type semiconductor layer 5 is sufficiently larger than the width W1 of the metal nanostructure 7, similar to the width W of the recess 8 of the second embodiment. On the other hand, the width W2b of the portion notching a part of the semiconductor optical absorption layer 3 is equal to or less than the wavelength of the incident light I, as in the third to fifth embodiments.

[0053] The depth Da of the notched portion of the semiconductor optical absorption layer 3 by the recess 8 is larger than the thickness T1 of the metal nanostructure 7 which is the scatterer 4, similar to the third embodiment. Therefore, the metal nanostructure 7 disposed on the bottom surface 8a of the recess 8 does not protrude toward the second conductivity type semiconductor layer 5 side from the surface where the second conductivity type semiconductor layer 5 is provided, and is in a state of being buried in the semiconductor optical absorption layer 3. In this photodetector 1F, in addition to the above-described operational effects, since the width W2a of the portion penetrating the second conductivity type semiconductor layer 5 is sufficiently larger than the width W1 of the metal nanostructure 7, the loss (loss due to scattering) of the incident light I by the second conductivity type semiconductor layer 5 can be reduced. This photodetector 1F is particularly suitable for the configuration of a surface incident type photodetector that irradiates light from the second conductivity type semiconductor layer 5 side. [Seventh Embodiment of Photodetector]

[0054] FIG. 7(a) is a schematic cross-sectional view showing the configuration of a photodetector according to the seventh embodiment of the present disclosure, and FIG. 7(b) is a plan view thereof. As shown in the figure, the photodetector 1G according to the seventh embodiment is further different from the sixth embodiment in that an insulating layer 15 is provided in the recess 8. The insulating layer 15 is formed of a material having a refractive index smaller than that of the semiconductor optical absorption layer 3. Examples of the material for forming the insulating layer 15 include silicon dioxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (Al 2 O 3 ), etc.

[0055] In the photodetector 1G, the depth D of the cutout portion of the semiconductor optical absorption layer 3 due to the recess 8 is smaller than the thickness T1 of the metal nanostructure 7 which is the scatterer 4. Therefore, in the photodetector 1G, the metal nanostructure 7 disposed on the bottom surface 8a of the recess 8 is in a state of slightly protruding toward the second conductive type semiconductor layer 5 side rather than the surface on which the second conductive type semiconductor layer 5 is provided. The insulating layer 15 is provided on the entire second surface 3b of the semiconductor optical absorption layer 3 exposed from the portion of the recess 8 that penetrates the second conductive type semiconductor layer 5 so as to be flush with the metal nanostructure 7 protruding toward the second conductive type semiconductor layer 5 side.

[0056] According to such a photodetector 1G, in addition to the above-described effects, protection of the scatterer 4 and prevention of leakage from the scatterer 4 can be realized by the insulating layer 15. Further, since the refractive index of the insulating layer 15 is smaller than the refractive index of the semiconductor optical absorption layer 3, a localized non-uniform electric field can be concentrated in the semiconductor optical absorption layer 3 having a relatively high refractive index. Therefore, further improvement in detection sensitivity can be achieved. [Eighth Embodiment of Photodetector]

[0057] Fig. 8(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the eighth embodiment of the present disclosure, and Fig. 8(b) is a plan view thereof. As shown in the figure, the photodetector 1H according to the eighth embodiment is further different from the third embodiment in that an insulating layer 15 is provided in the recess 8. The insulating layer 15 is formed of a material having a refractive index smaller than that of the semiconductor optical absorption layer 3, similar to the seventh embodiment. As the material for forming the insulating layer 15, for example, silicon dioxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (Al 2 O 3 ), etc. can be used.

[0058] In the photodetector 1H, the recess 8 is filled with the insulating layer 15, and the metal nanostructure 7 disposed on the bottom surface 8a of the recess 8 is covered with the insulating layer 15. Further, in the photodetector 1H, the insulating layer 15 is also provided on the entire surface of the second surface 5b of the second conductive type semiconductor layer 5 except for the formation region of the extraction electrode 6B.

[0059] According to such a photodetector 1H, in addition to the above-described effects, protection of the scatterer 4 and prevention of leakage from the scatterer 4 can be realized by the insulating layer 15. Further, since the refractive index of the insulating layer 15 is smaller than the refractive index of the semiconductor optical absorption layer 3, a local non-uniform electric field can be concentrated in the semiconductor optical absorption layer 3 having a relatively high refractive index. Therefore, further improvement in detection sensitivity can be achieved. [Ninth Embodiment of Photodetector]

[0060] Fig. 9(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the ninth embodiment of the present disclosure, and Fig. 9(b) is a plan view thereof. As shown in the figure, the photodetector 1I according to the ninth embodiment is different from the first embodiment in the planar shape of the recess 8.

[0061] In the photodetector 1I, the planar shape of the recess 8 is square. In the above-described first to eighth embodiments, the polarization direction of the incident light I corresponding to resonance is only in the width direction of the recess 8. However, in the photodetector 1I, resonance of the incident light I can also be supported in the direction orthogonal to the width direction of the recess. Therefore, it is possible to detect incident light I with polarization directions orthogonal to each other. The planar shape of the recess 8 is not limited to a square shape, and may be other shapes such as a circular shape. The planar shape of the recess 8 as shown in the ninth embodiment may also be applied to the above-described first to eighth embodiments. [Tenth Embodiment of Photodetector]

[0062] FIG. 10(a) is a schematic cross-sectional view showing the configuration of a photodetector according to the tenth embodiment of the present disclosure, and FIG. 10(b) is a plan view thereof. As shown in the figure, the photodetector 1J according to the tenth embodiment is different from the first embodiment in that a plurality of scatterers 4 are arranged at regular intervals in the in-plane direction of the interface between the scatterer 4 and the semiconductor optical absorption layer 3.

[0063] Specifically, in the photodetector 1J, a plurality (here, two) of recesses 8 are arranged in the width direction of the metal nanostructure 7. The planar shape of each recess 8 is rectangular and extends along the extending direction of the metal nanostructure 7. The adjacent recesses 8, 8 are spaced apart from each other, and the second conductivity type semiconductor layer 5 is located between the recesses 8, 8. According to such a photodetector 1J, the light reception area (area of the scatterer) of the incident light I is expanded, thereby improving the detection sensitivity. The arrangement of the scatterers 4 as shown in the tenth embodiment may also be applied to the above-described first to eighth embodiments. [Eleventh Embodiment of Photodetector]

[0064] FIG. 11(a) is a schematic cross-sectional view showing the configuration of a photodetector according to the eleventh embodiment of the present disclosure, and FIG. 11(b) is a plan view thereof. As shown in the figure, the photodetector 1K according to the eleventh embodiment is further different from the ninth embodiment in that a plurality of scatterers 4 are arranged at regular intervals in the in-plane direction of the interface between the scatterer 4 and the semiconductor optical absorption layer 3.

[0065] Specifically, in the photodetector 1K, a plurality (here, four) of recesses 8 are arranged in a lattice pattern. The planar shape of each recess 8 is rectangular and extends along the extending direction of the metal nanostructure 7. They are spaced apart from each other, and the second conductivity type semiconductor layer 5 is located between the recesses 8, 8. According to such a photodetector 1J, by expanding the light receiving region (the area of the scatterer) of the incident light I, the detection sensitivity can be improved. Also, similar to the ninth embodiment, it is possible to detect incident light I whose polarization directions are orthogonal to each other. The planar shape of the recess 8 is not limited to a square shape and may be other shapes such as a circular shape. The arrangement of the scatterer 4 as shown in the eleventh embodiment may be applied to the first to eighth embodiments described above. [12th Embodiment of Photodetector]

[0066] FIG. 12(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the 12th embodiment of the present disclosure, and FIG. 12(b) is a plan view thereof. As shown in the figure, the photodetector 1L according to the 12th embodiment is different from the third embodiment in that the conductivity type of the semiconductor light absorption layer 3 is inverted.

[0067] Specifically, in the photodetector 1L, the semiconductor light absorption layer 3 is made of, for example, n-type Si with a low carrier concentration and is composed of a high-resistance semiconductor (n-) with a low carrier concentration. The second conductivity type semiconductor layer 5 is made of, for example, p-type Si with a high carrier concentration and is composed of a low-resistance semiconductor (p+) with a high carrier concentration, similar to the third embodiment. In other embodiments, a pn junction is formed at the interface between the first conductivity type semiconductor layer 2 and the semiconductor light absorption layer 3, but in this embodiment, a pn junction is formed at the interface between the semiconductor light absorption layer 3 and the second conductivity type semiconductor layer 5. According to such a photodetector 1L, a pn junction can be easily formed. A semiconductor layer 5A composed of a high-resistance semiconductor (p-) with a low carrier concentration may be provided on the semiconductor light absorption layer 3 side in the second conductivity type semiconductor layer 5.

[0068] In addition, in the present embodiment, the thickness of the p-type semiconductor layer 5 including the semiconductor layer 5A is about several hundred nm, while the thickness of the semiconductor optical absorption layer 3 is as thick as about 50 μm. With such a configuration, in the photodetector 1L, a depletion layer can be expanded from the interface between the semiconductor optical absorption layer 3 and the p-type semiconductor layer 5 to a deep position in the semiconductor optical absorption layer 3. Therefore, when aligning the depletion layer position with the region where the electric field changes steeply due to the localized non-uniform electric field, it is not necessary to precisely adjust the depth of the concave portion 8, thus simplifying the manufacturing process.

[0069] In the photodetector 1L, an insulating layer 15 may be provided in the concave portion 8 as shown in the eighth embodiment. In this case, similar to the eighth embodiment, the insulating layer 15 can protect the scatterer 4 and prevent leakage from the scatterer 4. Further, since the refractive index of the insulating layer 15 is smaller than the refractive index of the semiconductor optical absorption layer 3, the localized non-uniform electric field can be concentrated on the semiconductor optical absorption layer 3 having a relatively high refractive index. Therefore, further improvement in detection sensitivity can be achieved. The insulating layer 15 can protect the scatterer 4 and prevent leakage from the scatterer 4. Furthermore, in the present embodiment, by filling the insulating layer 15 in the concave portion 8, the pn junction interface between the semiconductor optical absorption layer 3 and the p-type semiconductor layer 5 is covered with the insulating layer 15, so that the occurrence of side leakage from the interface can be suppressed. [13th Embodiment of Photodetector]

[0070] FIG. 13(a) is a schematic cross-sectional view showing the configuration of the photodetector according to the 13th embodiment of the present disclosure, and FIG. 13(b) is a plan view thereof. As shown in the figure, the photodetector 1M according to the 13th embodiment is different from the third embodiment in that a plurality (here, two) of concave portions 8 and metal nanostructures 7 disposed on the bottom surface 8a of the concave portions 8 are provided, and the incident light I is incident from the back surface side, which is a back-illuminated photodetector.

[0071] In the photodetector 1M, the concave portion 8 and the metal nanostructure 7 disposed on the bottom surface 8a of the concave portion 8 are provided at a predetermined interval in the width direction of the concave portion 8. A reflective film 31 is provided on the second surface 5b of the second-conductive-type semiconductor layer 5. In the examples of FIGS. 13(a) and 13(b), the reflective film 31 is provided on the second surface 5b at the edge of the concave portion 8 on the desired extraction electrode 6B side and on the whole between the concave portions 8, 8. Since the metal nanostructure 7 is located on the bottom surface 8a of the concave portion 8 and the reflective film 31 is located on the second surface 5b of the second-conductive-type semiconductor layer 5, the two are not electrically connected. According to such a photodetector 1M, among the incident light I incident from the back surface, the component transmitted through the scatterer 4 is reflected by the reflective film 31 and heads toward the semiconductor light absorption layer 3 again, so that the light absorption amount in the semiconductor light absorption layer 3 can be improved. [Manufacturing process of photodetector]

[0072] Subsequently, the manufacturing process of the photodetector will be described. Here, as representative examples, an example of the manufacturing process of the photodetector 1A according to the first embodiment, the photodetector 1C according to the third embodiment, and the photodetector 1D according to the fourth embodiment will be described respectively.

[0073] FIGS. 14 to 17 are schematic cross-sectional views showing an example of the manufacturing process of the photodetector 1A. In manufacturing the photodetector 1A, first, as shown in FIG. 14(a), a semiconductor substrate 21 of n-type conductivity is prepared. The semiconductor substrate 21 is subjected to ion implantation and heat treatment to perform impurity inversion of a part of the semiconductor substrate 21. Thereby, as shown in FIG. 14(b), a first-conductive-type semiconductor layer 2 of n-type conductivity and a semiconductor light absorption layer 3 of p-type conductivity are formed to form a pn junction. As the dopant, for example, boron (B), gallium (Ga), aluminum (Al), etc. can be used.

[0074] Next, ion implantation with an increased dose and heat treatment are performed on the semiconductor light absorption layer 3, and as shown in FIG. 14(c), a part of the semiconductor light absorption layer 3 is converted into a second conductivity type semiconductor layer 5 having a p-type conductivity type. After forming the second conductivity type semiconductor layer 5, as shown in FIG. 15(a), a metal layer 22 that will become the extraction electrode 6B is formed on the second conductivity type semiconductor layer 5. Next, as shown in FIG. 15(b), using photolithography, a resist R is patterned on the metal layer 22. After patterning the resist R, as shown in FIG. 15(c), the metal layer 22 exposed from the resist R is etched to form the extraction electrode 6B.

[0075] After forming the extraction electrode 6B, as shown in FIG. 16(a), using photolithography, a resist R is patterned on the second conductivity type semiconductor layer 5 so as to cover the extraction electrode 6B. After patterning the resist R, as shown in FIG. 16(b), the second conductivity type semiconductor layer 5 is etched to a depth at which the semiconductor light absorption layer 3 is exposed to form a recess 8. Examples of the material of the resist R include positive resists generally used in photolithography. As an etching method, for example, dry etching using sulfur hexafluoride (SF 6 ) and cyclobutane octafluoride (C 4 F 8 ) can be used.

[0076] After forming the recess 8, as shown in FIG. 17(a), using an electron beam lithography apparatus, the resist R is nano-patterned on the second conductivity type semiconductor layer 5, the extraction electrode 6B, and the semiconductor light absorption layer 3 exposed from the recess 8. After nano-patterning the resist R, as shown in FIG. 17(b), a layer that will become the scatterer 4 (here, the metal layer 23) is formed on the resist R and on the semiconductor light absorption layer 3 exposed from the resist R (the bottom surface 8a of the recess 8). As the material of the resist R, materials generally used in electron beam lithography can be used. Examples of such materials include non-chemically amplified positive electron beam resists and polymethyl methacrylate resins.

[0077] After forming the metal layer 23, the resist R and the metal layer 23 on the resist R are lifted off. As a result, as shown in FIG. 17(c), on the bottom surface 8a of the recess 8, a scatterer 4 (metal nanostructure 7) that contacts the semiconductor light absorption layer 3 and is separated from the second conductivity type semiconductor layer 5 and the extraction electrode 6B is formed. Finally, an extraction electrode 6A (see FIG. 1) is formed on the first conductivity type semiconductor layer 2 side to obtain the photodetector 1A shown in FIG. 1.

[0078] FIGS. 18 and 19 are schematic cross-sectional views showing an example of the manufacturing process of the photodetector 1C. In manufacturing the photodetector 1C, first, the steps shown in FIGS. 14(a) to 14(c) described above are performed to form the first conductivity type semiconductor layer 2, the semiconductor light absorption layer 3, and the second conductivity type semiconductor layer 5. Next, as shown in FIG. 18(a), using an electron beam lithography apparatus, the resist R is nanopatterned on the second conductivity type semiconductor layer 5. After the nanopatterning of the resist R, as shown in FIG. 18(b), the second conductivity type semiconductor layer 5 exposed from the resist R is etched to a depth that cuts out a part of the semiconductor light absorption layer 3 to form a recess 8.

[0079] After forming the recess 8, as shown in FIG. 18(c), a layer that becomes the scatterer 4 (here, the metal layer 23) is formed on the resist R and on the semiconductor light absorption layer 3 (the bottom surface 8a of the recess 8) exposed from the resist R. After forming the metal layer 23, the resist R and the metal layer 23 on the resist are lifted off. As a result, as shown in FIG. 19(a), on the bottom surface 8a of the recess 8, a scatterer 4 (metal nanostructure 7) that contacts the semiconductor light absorption layer 3 is formed.

[0080] Next, as shown in FIG. 19(b), using photolithography, the resist R is patterned on the second conductivity type semiconductor layer 5 and within the recess 8. After patterning the resist R, a metal layer 22 that becomes the extraction electrode 6B is formed on the second conductivity type semiconductor layer 5. After forming the metal layer 22, as shown in FIG. 19(c), the resist R is removed to form the extraction electrode 6B. Finally, an extraction electrode 6A (see FIG. 1) is formed on the first conductivity type semiconductor layer 2 side to obtain the photodetector 1C shown in FIG. 3.

[0081] Figs. 20 and 21 are schematic cross-sectional views showing an example of the manufacturing process of the photodetector 1D. In manufacturing the photodetector 1D, first, the steps shown in FIGS. 14(a) to 14(c), 18(a), and 18(b) described above are performed to form a recess 8 having a depth for notching a part of the semiconductor optical absorption layer 3 in the second conductivity type semiconductor layer 5. After the formation of the recess 8, as shown in FIG. 20(a), the resist R on the second conductivity type semiconductor layer 5 is removed.

[0082] Next, as shown in FIG. 20(b), using photolithography, the resist R is nanopatterned on the second conductivity type semiconductor layer 5 excluding the recess 8 and the opening edge portion 8c of the recess 8. After the formation of the resist R, as shown in FIG. 20(c), a layer to be the scatterer 4 (here, a non-conductive dielectric layer 25) is formed on the resist R, the bottom surface 8a, the inner wall surface 8b, and the opening edge portion 8c of the recess 8. After the formation of the non-conductive dielectric layer 25, the resist R and the non-conductive dielectric layer 25 on the resist are lifted off. As a result, as shown in FIG. 21(a), the scatterer 4 (non-conductive dielectric layer 25) in contact with the semiconductor optical absorption layer 3 is formed over the bottom surface 8a, the inner wall surface 8b, and the opening edge portion 8c of the recess 8.

[0083] After the formation of the scatterer 4, as shown in FIG. 21(b), using photolithography, the resist R is patterned on the second conductivity type semiconductor layer 5, on the scatterer 4, and in the recess 8. After the patterning of the resist R, a metal layer 22 to be the extraction electrode 6B is formed on the second conductivity type semiconductor layer 5. After the formation of the metal layer 22, as shown in FIG. 21(c), the resist R is removed to form the extraction electrode 6B. Finally, an extraction electrode 6A (see FIG. 1) is formed on the side of the first conductivity type semiconductor layer 2 to obtain the photodetector 1D shown in FIG. 4. [Modification Example]

[0084] The present disclosure is not limited to the above-described embodiments. For example, in the above-described embodiments, each semiconductor layer is exemplified with the first conductivity type being n-type and the second conductivity type being p-type, but the first conductivity type may be p-type and the second conductivity type may be n-type.

[0085] In addition, in the above embodiments, except for the fourth embodiment, the metal nanostructure 7 that generates surface plasmon resonance was shown as an example of the scatterer 4. However, in other embodiments, the scatterer 4 may also be a dielectric nanostructure 10. As the material of the dielectric nanostructure, it is preferable to use a semiconductor material or an insulating material in consideration of the ease of film formation. Examples of the semiconductor material include germanium (Ge), silicon (Si), germanium silicon (GeSi), germanium tin (GeSn), gallium arsenide (GaAs), and the like. The scatterer 4 may be composed of fine particles of a metal or a dielectric. Examples of the metal fine particles include fine particles of gold (Au), silver (Ag), copper (Cu), aluminum (Al), and the like. Examples of the dielectric fine particles include silica spheres, alumina spheres, titanium oxide spheres, and the like.

Explanation of Reference Numerals

[0086] 1A to 1M... photodetectors, 2... first conductivity type semiconductor layer, 3... semiconductor optical absorption layer, 4... scatterer, 5... second conductivity type semiconductor layer, 6B... extraction electrode, 7... metal nanostructure (scatterer), 8... recess, 8a... bottom surface, 8b... inner wall surface, 10... dielectric nanostructure (scatterer), 11... first layer, 12... second layer, 13... third layer, 15... insulating layer, 31... reflective film, I... incident light.

Claims

1. A first conductivity type semiconductor layer; a semiconductor light absorbing layer provided on the first conductive type semiconductor layer; a scatterer that is provided in contact with the semiconductor light absorbing layer and has a width equal to or smaller than the wavelength of incident light, and that scatters the incident light to form a localized non-uniform electric field inside the semiconductor light absorbing layer; a second conductive type semiconductor layer provided on the semiconductor light absorbing layer at a distance from the scatterer; an extraction electrode provided on the second conductive type semiconductor layer at a distance from the scatterer, for extracting a photocurrent generated in the semiconductor light absorption layer by the formation of the localized non-uniform electric field; the second conductive type semiconductor layer is provided with a recess that penetrates the second conductive type semiconductor layer and cuts out a part of the semiconductor light absorbing layer; The scatterer is a photodetector disposed on the bottom surface of the recess.

2. A first conductivity type semiconductor layer; a semiconductor light absorbing layer provided on the first conductive type semiconductor layer; a scatterer that is provided in contact with the semiconductor light absorbing layer and has a width equal to or smaller than the wavelength of incident light, and that scatters the incident light to form a localized non-uniform electric field inside the semiconductor light absorbing layer; a second conductive type semiconductor layer provided on the semiconductor light absorbing layer at a distance from the scatterer; an extraction electrode provided on the second conductive type semiconductor layer at a distance from the scatterer, for extracting a photocurrent generated in the semiconductor light absorption layer by the formation of the localized non-uniform electric field; the second conductive type semiconductor layer is provided with a recess that penetrates the second conductive type semiconductor layer and cuts out a part of the semiconductor light absorbing layer; The scatterer is a photodetector disposed across the bottom surface and the inner wall surface of the recess.

3. 3. The photodetector according to claim 1, wherein the scatterer is a metal nanostructure that generates surface plasmon resonance near the interface between the scatterer and the semiconductor light absorbing layer.

4. the semiconductor light absorbing layer is composed of a first layer having a p-type conductivity, a second layer having an i-type conductivity, and a third layer having an n-type conductivity; The recess is provided with a depth that cuts out a part of the second layer, 2. The photodetector according to claim 1, wherein the scatterer is disposed on the bottom surface of the recess so as to be embedded in the second layer.

5. 5. The photodetector according to claim 1, wherein the width of the recess is equal to or less than the wavelength of the incident light over the entire depth direction.

6. 6. The photodetector according to claim 1, wherein the width of the recess that penetrates the second conductivity type semiconductor layer is greater than the width of the portion that cuts out a portion of the semiconductor light absorbing layer.

7. 7. The photodetector according to claim 1, wherein an insulating layer made of a material having a refractive index smaller than that of said semiconductor light absorbing layer is provided within said recess.

8. 8. The photodetector according to claim 1, wherein a plurality of the scatterers are provided at regular intervals in an in-plane direction of the interface between the scatterer and the semiconductor light absorbing layer.

9. a back-illuminated photodetector into which the incident light is incident from the first conductivity type semiconductor layer side, The photodetector according to any one of claims 1 to 8, wherein a reflective film is provided on the second conductive type semiconductor layer, which reflects a component of the incident light incident on the back surface that has passed through the scatterer toward the semiconductor light absorption layer side.

Images