Light detector and electronic device

Abstract

A light detector (1) according to an embodiment of the present disclosure comprises: a first electrode (23); a second electrode (26) provided so as to face the first electrode (23); a photoelectric conversion film (22) provided between the first electrode (23) and the second electrode (26); a first semiconductor layer (25a) provided between the photoelectric conversion film (22) and the second electrode (26); and a second semiconductor layer (25b) provided between the first semiconductor layer (25a) and the second electrode (26). The difference between the energy level of the lower end of the conduction band and the Fermi level in the first semiconductor layer (25a) is smaller than the difference between the energy level of the lower end of the conduction band and the Fermi level in the second semiconductor layer (25b).

Description

Photodetector and electronic equipment

[0001] The present disclosure relates to photodetection devices and electronic equipment.

[0002] An imaging device has been proposed that has a plurality of photoelectric conversion layers and performs photoelectric conversion on light of each color (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2017-157816

[0004] In light detecting devices, it is required to suppress degradation of signal quality.

[0005] It is desirable to provide a photodetector that can suppress degradation of signal quality.

[0006] A photodetector according to an embodiment of the present disclosure includes a first electrode, a second electrode disposed opposite the first electrode, a photoelectric conversion film disposed between the first electrode and the second electrode, a first semiconductor layer disposed between the photoelectric conversion film and the second electrode, and a second semiconductor layer disposed between the first semiconductor layer and the second electrode. The difference between the energy level of the conduction band minimum and the Fermi level in the first semiconductor layer is smaller than the difference between the energy level of the conduction band minimum and the Fermi level in the second semiconductor layer. An electronic device according to an embodiment of the present disclosure includes an optical system and a photodetector configured to receive light transmitted through the optical system. The photodetector includes a first electrode, a second electrode disposed opposite the first electrode, a photoelectric conversion film disposed between the first electrode and the second electrode, a first semiconductor layer disposed between the photoelectric conversion film and the second electrode, and a second semiconductor layer disposed between the first semiconductor layer and the second electrode. The difference between the energy level of the conduction band minimum and the Fermi level in the first semiconductor layer is smaller than the difference between the energy level of the conduction band minimum and the Fermi level in the second semiconductor layer.

[0007] FIG. 1 is a block diagram illustrating an example of a schematic configuration of an imaging device that is an example of a photodetector according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a pixel unit of the imaging device according to the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a cross-sectional configuration of the imaging device according to the first embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example of a circuit configuration of a pixel of the imaging device according to the first embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example of a planar configuration of the imaging device according to the first embodiment of the present disclosure. FIG. 6 is a diagram illustrating an example of a configuration of the imaging device according to the first embodiment of the present disclosure. FIG. 7 is a diagram illustrating an example of energy levels in the imaging device according to the first embodiment of the present disclosure. FIG. 8A is a diagram illustrating an example of a manufacturing method of the imaging device according to the first embodiment of the present disclosure. FIG. 8B is a diagram illustrating an example of a manufacturing method of the imaging device according to the first embodiment of the present disclosure. FIG. 8C is a diagram illustrating an example of a manufacturing method of the imaging device according to the first embodiment of the present disclosure. FIG. 8D is a diagram illustrating an example of a manufacturing method of the imaging device according to the first embodiment of the present disclosure. FIG. 9 is a diagram illustrating another example of a configuration of the imaging device according to the first embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example of energy levels in an imaging device according to a first embodiment of the present disclosure. FIG. 11 is a timing chart illustrating an example of operation of an imaging device according to a first embodiment of the present disclosure. FIG. 12 is a diagram illustrating an example of a cross-sectional configuration of an imaging device according to a first modification of the present disclosure. FIG. 13 is a diagram illustrating an example of a planar configuration of an imaging device according to a first modification of the present disclosure. FIG. 14 is a diagram illustrating another example of a configuration of an imaging device according to a first modification of the present disclosure. FIG. 15 is a diagram illustrating another example of a configuration of an imaging device according to a first modification of the present disclosure. FIG. 16 is a diagram illustrating an example of a cross-sectional configuration of an imaging device according to a second modification of the present disclosure. FIG. 17 is a diagram illustrating an example of energy levels in an imaging device according to a second modification of the present disclosure. FIG. 18 is a diagram illustrating an example of a cross-sectional configuration of an imaging device according to a third modification of the present disclosure. FIG. 19 is a diagram illustrating an example of energy levels in an imaging device according to a third modification of the present disclosure. FIG. 20 is a diagram illustrating an example of a configuration of an imaging device according to a fourth modification of the present disclosure.FIG. 21 is a diagram illustrating a configuration example of an imaging device according to Modification 5 of the present disclosure. FIG. 22 is a diagram illustrating a configuration example of an imaging device according to Modification 6 of the present disclosure. FIG. 23A is a diagram illustrating a configuration example of an imaging device according to Modification 6 of the present disclosure. FIG. 23B is a diagram illustrating a configuration example of an imaging device according to Modification 6 of the present disclosure. FIG. 24 is a diagram illustrating a configuration example of an imaging device according to a second embodiment of the present disclosure. FIG. 25 is a diagram illustrating an example of energy levels in an imaging device according to the second embodiment of the present disclosure. FIG. 26 is a diagram illustrating another configuration example of an imaging device according to the second embodiment of the present disclosure. FIG. 27 is a diagram illustrating an example of energy levels in an imaging device according to the second embodiment of the present disclosure. FIG. 28A is a diagram illustrating an example of a cross-sectional configuration of an imaging device according to Modification 7 of the present disclosure. FIG. 28B is a diagram illustrating an example of a cross-sectional configuration of an imaging device according to Modification 7 of the present disclosure. FIG. 29 is a diagram illustrating an example of a cross-sectional configuration of an imaging device according to Modification 8 of the present disclosure. FIG. 30 is a diagram illustrating an example of energy levels in an imaging device according to Modification 8 of the present disclosure. Fig. 31 is a block diagram showing an example of the configuration of an electronic device. Fig. 32A is a schematic representation of an example of the overall configuration of a light detection system. Fig. 32B is a schematic representation of an example of the overall configuration of a light detection system. Fig. 33 is a block diagram showing an example of the general configuration of a vehicle control system. Fig. 34 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit. Fig. 35 is a diagram showing an example of the general configuration of an endoscopic surgery system. Fig. 36 is a block diagram showing an example of the functional configuration of a camera head and a CCU.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order: 1. First embodiment 2. Second embodiment 3. Application example 4. Application example

[0009] 1. First Embodiment Fig. 1 is a block diagram showing an example of a schematic configuration of an imaging device which is an example of a photodetector according to a first embodiment of the present disclosure. Fig. 2 is a diagram showing an example of a pixel unit of the imaging device according to the first embodiment. The photodetector is a device capable of detecting incident light. An imaging device 1 which is an example of a photodetector has a plurality of pixels P each having a photoelectric conversion unit (photoelectric conversion element) and is configured to photoelectrically convert incident light to generate a signal. The imaging device 1 can generate a signal by receiving light which has passed through an optical system (not shown) including an optical lens, for example.

[0010] The imaging device 1 is configured, for example, using a semiconductor substrate on which a plurality of pixels P are provided. Each pixel P of the imaging device 1 includes, for example, a photodiode (PD) as a photoelectric conversion unit and is configured to be capable of photoelectrically converting light. As shown in the example of FIG. 2 , the imaging device 1 has, as an imaging area, a region (pixel unit 100) in which a plurality of pixels P are two-dimensionally arranged in a matrix. The pixel unit 100 can also be said to be a pixel array in which a plurality of pixels P are arranged.

[0011] The imaging device 1 captures incident light (image light) from a subject to be measured via an optical system including an optical lens. The imaging device 1 captures an image of the subject formed by the optical lens. The imaging device 1 can generate pixel signals by photoelectrically converting the received light (e.g., visible light, infrared light, etc.). The imaging device 1, which is a photodetector, is a device that can receive incident light and generate a signal, and can also be called a light-receiving device.

[0012] The imaging device 1 (photodetector) may be configured as an image sensor, for example. The imaging device 1 may be, for example, a complementary metal oxide semiconductor (CMOS) image sensor. The imaging device 1 may have a structure (a stacked structure) formed by stacking multiple semiconductor layers. The imaging device 1 may be used in various electronic devices, such as digital still cameras, video cameras, and mobile phones.

[0013] 2, the incident direction of light from the subject is defined as the Z-axis direction, the left-right direction on the paper surface perpendicular to the Z-axis direction is defined as the X-axis direction, and the up-down direction on the paper surface perpendicular to the Z-axis and X-axis directions is defined as the Y-axis direction. In the following figures, directions may be indicated based on the direction of the arrow in FIG. 2.

[0014] 1 , the imaging device 1 includes, for example, a vertical drive circuit 111, a signal processing circuit 112, a horizontal drive circuit 113, an output circuit 114, a control circuit 115, and an input / output terminal 116 in a peripheral region of a pixel unit 100 (pixel array). The imaging device 1 also includes, for example, a plurality of control lines Lread and a plurality of signal lines VSL.

[0015] The control lines Lread are signal lines capable of transmitting signals for controlling the pixels P, and are connected to the vertical drive circuit 111 and the pixels P of the pixel unit 100. In the example shown in FIG. 1 , a plurality of control lines Lread are wired in the pixel unit 100 for each pixel row made up of a plurality of pixels P aligned in the horizontal direction (row direction). The control lines Lread are configured to transmit control signals for reading out signals from the pixels P.

[0016] The plurality of control lines Lread for each pixel row of the imaging device 1 include, for example, wiring for transmitting signals that control transfer transistors, wiring for transmitting signals that control selection transistors, wiring for transmitting signals that control reset transistors, etc. The control lines Lread can also be said to be drive lines (pixel drive lines) that transmit signals that drive the pixels P.

[0017] The signal line VSL is a signal line capable of transmitting a signal from the pixel P, and is connected to the pixel P of the pixel unit 100 and the signal processing circuit 112. In the pixel unit 100, for example, one or more signal lines VSL are wired for each pixel column formed by a plurality of pixels P aligned in the vertical direction (column direction).

[0018] The signal lines VSL are vertical signal lines configured to transmit signals output from the pixels P. In the imaging device 1, multiple signal lines VSL (for example, three signal lines VSL1 to VSL3) may be provided for one pixel column. The imaging device 1 may have multiple signal lines VSL for each pixel column.

[0019] The vertical drive circuit 111 is configured to be able to drive each pixel P of the pixel unit 100. The vertical drive circuit 111 is configured with a plurality of circuits including, for example, a buffer, a shift register, an address decoder, etc. The vertical drive circuit 111 generates a signal for driving the pixel P and outputs the signal to each pixel P of the pixel unit 100 via a control line Lread. The vertical drive circuit 111 is controlled by a control circuit 115, and controls the pixels P of the pixel unit 100.

[0020] The vertical drive circuit 111 generates, for example, a signal for controlling a selection transistor, a signal for controlling a reset transistor, etc., and supplies these signals to each pixel P via a control line Lread. The vertical drive circuit 111 can control the reading of pixel signals from each pixel P. The vertical drive circuit 111 can also be said to be a pixel control unit configured to be able to control each pixel P.

[0021] The signal processing circuit 112 is configured to be able to perform signal processing of input pixel signals. The signal processing circuit 112 includes, for example, a load circuit, an AD (Analog-Digital) conversion circuit, a horizontal selection switch, etc. As an example, the load circuit is configured by a current source capable of supplying current to the amplification transistor of the pixel P. The load circuit, together with the amplification transistor of the pixel P, forms, for example, a source follower circuit.

[0022] The signal processing circuit 112 may have an amplifier circuit configured to amplify signals read out from the pixels P via the signal lines VSL. A load circuit, an amplifier circuit, an AD conversion circuit, etc. are provided for each of the multiple signal lines VSL, for example. A load circuit, an amplifier circuit, an AD conversion circuit, etc. may be provided for each pixel column of the pixel unit 100.

[0023] The signals output from each pixel P selected and scanned by the vertical drive circuit 111 are input via a signal line VSL to a signal processing circuit 112. The signal processing circuit 112 performs signal processing such as AD conversion of the signal from the pixel P and CDS (Correlated Double Sampling).

[0024] The horizontal drive circuit 113 is composed of, for example, a buffer, a shift register, an address decoder, etc. The horizontal drive circuit 113 is configured to be able to drive the horizontal selection switches of the signal processing circuit 112. The horizontal drive circuit 113 drives each horizontal selection switch of the signal processing circuit 112 in sequence while scanning them. The signals of each pixel P transmitted through each signal line VSL are subjected to signal processing by the signal processing circuit 112 and output to the horizontal signal line 121 in sequence by selective scanning by the horizontal drive circuit 113.

[0025] The output circuit 114 is configured to perform signal processing on an input signal and output the signal. The output circuit 114 performs signal processing on pixel signals sequentially input from the signal processing circuit 112 via the horizontal signal line 121, and outputs the processed pixel signals. The output circuit 114 can perform, for example, buffering, black level adjustment, column variation correction, various types of digital signal processing, and the like.

[0026] The control circuit 115 is configured to be able to control each part of the imaging device 1. The control circuit 115 receives externally provided clocks, data instructing the operation mode, etc., and can also output data such as internal information of the imaging device 1. The control circuit 115 has, for example, a timing generator configured to be able to generate various timing signals.

[0027] The control circuit 115 controls the driving of peripheral circuits such as the vertical drive circuit 111, the signal processing circuit 112, and the horizontal drive circuit 113 based on various timing signals (pulse signals, clock signals, etc.) generated by the timing generator. The input / output terminals 116 exchange signals with the outside.

[0028] The vertical drive circuit 111, the signal processing circuit 112, the horizontal drive circuit 113, the horizontal signal line 121, the output circuit 114, the control circuit 115, etc. may be provided on a single semiconductor substrate or may be provided separately on multiple semiconductor substrates. The imaging device 1 may have a structure (a stacked structure) formed by stacking multiple substrates.

[0029] Fig. 3 is a diagram illustrating an example of a cross-sectional configuration of the imaging device according to the first embodiment. Fig. 4 is a diagram illustrating an example of a circuit configuration of a pixel of the imaging device according to the first embodiment. As shown in Fig. 3, the imaging device 1 includes, for example, a light receiving unit 10 and a light receiving unit 20.

[0030] The light receiving unit 10 is provided on layer 101 of the multiple stacked layers. The light receiving unit 20 is provided on layer 102. Layer 102 having the light receiving unit 20 is located above layer 101 having the light receiving unit 10. The imaging device 1 has a configuration in which layer 101 having the light receiving unit 10 and layer 102 having the light receiving unit 20 are stacked in the Z-axis direction.

[0031] Each pixel P of the imaging device 1 has a plurality of stacked photoelectric conversion units (photoelectric conversion elements). The photoelectric conversion units are configured to receive light and generate signals. In the example shown in Figures 3 and 4, the pixel P has a photoelectric conversion unit 11a, a photoelectric conversion unit 11b, and a photoelectric conversion unit 11c. The pixel P has a structure in which the photoelectric conversion units 11a, 11b, and 11c are stacked.

[0032] The photoelectric conversion units 11a and 11b are configured by, for example, photodiodes (PDs). The photoelectric conversion unit 11c has a photoelectric conversion film 22. The photoelectric conversion units 11a, 11b, and 11c are each configured to be able to generate charges by photoelectric conversion. The imaging device 1 has a light receiving unit 10 including the photoelectric conversion units 11a and 11b, and a light receiving unit 20 including the photoelectric conversion unit 11c.

[0033] The light receiving unit 10 is formed using a semiconductor layer 110. As shown in Fig. 3, the semiconductor layer 110 has a surface 11S1 and a surface 11S2 that face each other. The surface 11S2 of the semiconductor layer 110 is the surface opposite to the surface 11S1. The semiconductor layer 110 is formed of a semiconductor substrate, for example, a Si (silicon) substrate.

[0034] The semiconductor layer 110 may be an SOI (Silicon On Insulator) substrate, a SiGe (Silicon Germanium) substrate, a SiC (Silicon Carbide) substrate, or may be formed using other semiconductor materials. The semiconductor layer 110 may be made of a III-V group compound semiconductor material, or the like.

[0035] The surface 11S1 of the semiconductor layer 110 is a light-receiving surface (light incident surface). The surface 11S2 of the semiconductor layer 110 is an element formation surface on which elements such as transistors are formed. A gate electrode, a gate insulating film (e.g., a gate oxide film), etc. may be provided on the surface 11S2 of the semiconductor layer 110.

[0036] 3, the light receiving unit 20 is provided on the surface 11S1 side of the semiconductor layer 110. The wiring layer 120 is provided on the surface 11S2 side of the semiconductor layer 110. The lens 81, the light receiving unit 20, etc. are provided on the side where light from the optical system is incident, and the wiring layer 120 is provided on the side opposite to the side where the light is incident.

[0037] In the semiconductor layer 110, a plurality of photoelectric conversion units 11a and a plurality of photoelectric conversion units 11b are provided along a surface 11S1 and a surface 11S2 of the semiconductor layer 110. For example, a plurality of photoelectric conversion units 11a and a plurality of photoelectric conversion units 11b are embedded in the semiconductor layer 110. The photoelectric conversion units 11a and the photoelectric conversion units 11b are each a photodiode (PD) that converts incident light into an electric charge.

[0038] As shown in Fig. 3, the semiconductor layer 110 has a well 13. The well 13 is, for example, a p-type semiconductor region, or a p-type well (p-well). In the example shown in Fig. 3, the well 13, which is a p-type well region, is provided in the semiconductor layer 110. The well 13 is provided with a semiconductor region 16, a semiconductor region 17, and a semiconductor region 18.

[0039] 3, the semiconductor region 16 is provided on the surface 11S2 side of the semiconductor layer 110, and the semiconductor region 17 is provided on the surface 11S1 side of the semiconductor layer 110.

[0040] The semiconductor region 18 has, for example, an impurity concentration higher than the impurity concentration of the well 13, and is a p+ type semiconductor region. In the example shown in Figure 3, a part of the semiconductor region 18 is provided between the semiconductor region 16 and the semiconductor region 17, and another part of the semiconductor region 18 is provided on the surface 11S2 side of the semiconductor layer 110. The photoelectric conversion unit 11a is configured to include the semiconductor region 16 provided in the well 13.

[0041] The photoelectric conversion unit 11b includes a semiconductor region 17 provided in the well 13. The photoelectric conversion unit 11b is formed in the semiconductor layer 110 so as to be stacked on the photoelectric conversion unit 11a. The photoelectric conversion unit 11b is provided on the light incident side of the photoelectric conversion unit 11a. The photoelectric conversion units 11a and 11b each perform photoelectric conversion to generate charges according to the amount of received light. The photoelectric conversion units 11a and 11b of each pixel P can also be referred to as photoelectric conversion regions.

[0042] The photoelectric conversion units 11 a and 11 b may be configured to perform photoelectric conversion on light in different wavelength ranges. The photoelectric conversion units 11 a and 11 b selectively receive and photoelectrically convert light in specific wavelength ranges depending on, for example, the positions at which the photoelectric conversion units 11 a and 11 b are provided in the semiconductor layer 110, the constituent materials, and the like.

[0043] The photoelectric conversion units 11a and 11b are located at different distances (depths) from the surface 11S1 of the semiconductor layer 110, and generate charges by absorbing light of different color wavelengths depending on the incident depth (penetration depth) of the light. In the example shown in Fig. 3, the photoelectric conversion unit 11a is located below the photoelectric conversion unit 11b, and can generate charges by photoelectrically converting light that passes through the photoelectric conversion unit 11b.

[0044] Furthermore, in the semiconductor layer 110, a plurality of floating diffusions (floating diffusions FD1, FD2, and FD3 in the examples shown in FIGS. 3 and 4) are provided for each pixel P or for each set of pixels P. Each of the floating diffusions FD1 to FD3 is configured to include, for example, an n-type semiconductor region.

[0045] The wiring layer 120 includes, for example, a conductor film and an insulating film, and has a plurality of wires and vias (VIAs), etc. The wiring layer 120 is a multi-layer wiring layer, and includes, for example, two or more layers of wires, or three or more layers of wires. The wiring layer 120 has a configuration in which a plurality of wires are stacked with an insulating film interposed therebetween as an interlayer insulating film (interlayer insulating layer).

[0046] The wiring of the wiring layer 120 is formed using a metal material such as aluminum (Al), tungsten (W), or copper (Cu). The wiring of the wiring layer 120 may be formed using polysilicon (Poly-Si) or other conductive materials. The interlayer insulating film is formed using, for example, silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), or the like.

[0047] In the semiconductor layer 110 and the wiring layer 120, for example, a plurality of readout circuits 15 (readout circuits 15a, 15b, and 15c in the example shown in FIG. 4 ) are provided for each pixel P or for each plurality of pixels P. Note that the above-mentioned vertical drive circuit 111, signal processing circuit 112, horizontal drive circuit 113, horizontal signal line 121, output circuit 114, control circuit 115, etc. may be provided on a substrate separate from the semiconductor layer 110, or on the semiconductor layer 110 and the wiring layer 120.

[0048] The lens 81 is a lens that focuses light and is an optical component also called an on-chip lens. The lens 81 is made of, for example, silicon oxide, silicon nitride, silicon oxynitride, or the like. Note that the lens 81 may also be made of other light-transmitting materials.

[0049] The lens 81 (lens portion) is provided above the semiconductor layer 110, for example, for each pixel P or for each set of multiple pixels P. Light from a subject to be measured is incident on the lens 81 via an optical system such as an imaging lens. The lens 81 guides the incident light toward the semiconductor layer 110.

[0050] In the imaging device 1, the photoelectric conversion units 11a, 11b, and 11c each photoelectrically convert light incident thereon via the lens 81. Each of the photoelectric conversion units 11a, 11b, and 11c can absorb the incident light and generate electric charges.

[0051] Transistor TR1, transistor TR2, floating diffusions FD1 to FD3, etc. are provided on the surface 11S2 side of the semiconductor layer 110. The transistor TR1 has a gate electrode 45 and is provided for the photoelectric conversion unit 11a. The transistor TR1 is a transfer transistor and is configured to be able to transfer charges photoelectrically converted by the photoelectric conversion unit 11a to the floating diffusion FD1.

[0052] The transistor TR2 has a gate electrode 46 and a gate insulating film 47, and is provided for the photoelectric conversion unit 11b. The transistor TR2 is a transfer transistor and is configured to be able to transfer charges photoelectrically converted by the photoelectric conversion unit 11b to the floating diffusion FD2. For example, the transistor TR2 has a vertical gate structure. At least a portion of each of the gate electrode 46 and the gate insulating film 47 is provided within the semiconductor layer 110.

[0053] 3 , at least a portion of each of the gate electrode 46 and the gate insulating film 47 is provided by, for example, recessing the semiconductor layer 110. The transistor TR2 can also be called a vertical transistor. A portion of each of the gate electrode 46 and the gate insulating film 47 can be disposed so as to be embedded in the semiconductor layer 110.

[0054] The gate electrode 46 of the transistor TR2 is provided, for example, to extend in the thickness direction of the semiconductor layer 110. The gate electrode 46 and gate insulating film 47 of the transistor TR2 are, for example, formed in the semiconductor layer 110 to reach the photoelectric conversion unit 11b. In the example shown in Fig. 3, a portion of the gate electrode 46 of the transistor TR2 extends from the surface 11S2 of the semiconductor layer 110 toward the inside of the semiconductor layer 110, and is provided up to the region of the photoelectric conversion unit 11b.

[0055] The gate electrode 45 of the transistor TR1 and the gate electrode 46 of the transistor TR2 are each made of, for example, polysilicon (Poly-Si). The gate electrodes 45 and 46 may also be made of a metal material or a metal compound. The gate electrodes 45 and 46 may also be made of, for example, titanium nitride (TiN), tantalum nitride (TaN), tungsten (W), or the like.

[0056] The gate insulating film 47 is configured by, for example, a single layer film made of one kind of silicon oxide (SiO), silicon oxynitride (SiON), hafnium oxide (HfO), etc., or a laminated film made of two or more kinds of these. The gate insulating film 47 may be formed using a high-dielectric-constant material having a dielectric constant higher than that of silicon oxide, such as a hafnium-based insulating film.

[0057] The light receiving section 20 of the imaging device 1 has a plurality of photoelectric conversion sections 11c. As shown in the example of FIG. 3, the photoelectric conversion section 11c of each pixel P includes a photoelectric conversion film 22, an upper electrode 23, and a readout electrode 24. The photoelectric conversion section 11c also has a semiconductor layer 25a, a semiconductor layer 25b, and a storage electrode 26. Furthermore, the light receiving section 20 of the imaging device 1 may have a protective layer 29 as shown in the example of FIG. 3.

[0058] The photoelectric conversion film 22 generates electric charges through photoelectric conversion. The photoelectric conversion film 22 photoelectrically converts incident light and can generate electric charges according to the amount of light received. The photoelectric conversion film 22 can also be called a photoelectric conversion layer. The photoelectric conversion film 22 (photoelectric conversion layer) is, for example, a photoelectric conversion film made of an organic material.

[0059] In the imaging device 1, for example, a photoelectric conversion film 22 made of an organic semiconductor material is provided in each pixel P. A photoelectric conversion film made of an inorganic material may be disposed as the photoelectric conversion film 22. The material of the photoelectric conversion film 22 may be selected depending on, for example, the wavelength range of incident light to be measured.

[0060] The upper electrode 23 is, for example, an electrode common to the photoelectric conversion films 22 of multiple pixels P, and is provided on one side of the photoelectric conversion film 22. In each pixel P, a readout electrode 24 and a storage electrode 26 are provided for the photoelectric conversion film 22. The readout electrode 24 and the storage electrode 26 are provided on the other side of the photoelectric conversion film 22 for each pixel P or for each set of multiple pixels P. The readout electrode 24 and the storage electrode 26 are electrodes used to control the charges photoelectrically converted in the photoelectric conversion film 22.

[0061] 3 , the upper electrode 23 and the readout electrode 24 are arranged to sandwich the photoelectric conversion film 22, the protective layer 29, and the semiconductor layers 25 a and 25 b. The readout electrode 24 is provided to face the upper electrode 23, sandwiching portions of the semiconductor layers 25 a and 25 b, the protective layer 29, and the photoelectric conversion film 22. The upper electrode 23 is an electrode above the photoelectric conversion film 22, and the readout electrode 24 is an electrode below the photoelectric conversion film 22.

[0062] The upper electrode 23 is an electrode common to a plurality of pixels P and can also be called a common electrode. The readout electrode 24 can also be called a lower electrode. The upper electrode 23, readout electrode 24, storage electrode 26, etc. are electrically connected to circuits provided in the semiconductor layer 110 and wiring layer 120 via, for example, different wirings, electrodes, etc.

[0063] The readout electrode 24 and the storage electrode 26 are provided on an insulating layer 131. The insulating layer 131 is provided on the surface 11S1 of the semiconductor layer 110. The insulating layer 131 is formed using an insulating film such as an oxide film, a nitride film, or an oxynitride film. The insulating layer 131 may be made of silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), or the like, or may be made using another material that transmits light to be measured.

[0064] The protective layer 29 is, for example, a protective layer containing an inorganic material, and is provided between the photoelectric conversion film 22 and the semiconductor layer 25a. In the example shown in Fig. 3, the protective layer 29 is formed between the photoelectric conversion film 22 and the semiconductor layer 25a and is located on the semiconductor layer 25a. The protective layer 29 can also be called a passivation film (protective film).

[0065] The protective layer 29 is a layer containing at least one of, for example, Ti (titanium), Si (silicon), Zr (zirconium), Nb (niobium), V (vanadium), Ta (tantalum), Hf (hafnium), Al (aluminum), Sn (tin), Sc (scandium), Y (yttrium), La (lanthanoid), Ga (gallium), and Mg (magnesium).

[0066] The semiconductor layer 25a and the semiconductor layer 25b are provided between the insulating layer 131, on which the readout electrode 24, the storage electrode 26, etc. are provided, and the photoelectric conversion film 22. In the example shown in FIG. 3, the semiconductor layer 25a and the semiconductor layer 25b are located between the insulating layer 131 and the protective layer 29. The semiconductor layer 25a and the semiconductor layer 25b are layers used for storing and transferring charges photoelectrically converted by the photoelectric conversion film 22, and can also be called charge storage and transfer layers. The semiconductor layer 25a and the semiconductor layer 25b are arranged to face the photoelectric conversion film 22.

[0067] The semiconductor layer 25a and the semiconductor layer 25b are each, for example, a semiconductor layer containing an oxide semiconductor. The semiconductor layer 25a is provided, for example, between the photoelectric conversion film 22 and the semiconductor layer 25b. In the example shown in Fig. 3, the semiconductor layer 25a is located between the protective layer 29 and the semiconductor layer 25b and is formed on the semiconductor layer 25b. For example, the semiconductor layer 25a is provided in contact with the protective layer 29.

[0068] The semiconductor layer 25b is formed between the insulating layer 131, on which the readout electrode 24, the storage electrode 26, etc. are provided, and the semiconductor layer 25a. As in the example shown in Fig. 3, the semiconductor layer 25b is provided between the semiconductor layer 25a and the storage electrode 26 and between the semiconductor layer 25a and the readout electrode 24. The semiconductor layer 25b can be provided in contact with the semiconductor layer 25a.

[0069] The semiconductor layer 25a may be configured to have a high carrier concentration (carrier density). For example, the semiconductor layer 25a may be configured to have a carrier concentration higher (larger) than the carrier concentration of the semiconductor layer 25b. When the carrier concentration of the semiconductor layer 25a is N1 and the carrier concentration of the semiconductor layer 25b is N2, the semiconductor layer 25a and the semiconductor layer 25b may be formed so that N1 > N2.

[0070] For example, the carrier concentration N1 (carrier density) of the semiconductor layer 25a is 1×10 １８ cm －３ The carrier concentration N2 of the semiconductor layer 25b may be 1×10 １８ cm －３ In the imaging device 1, the semiconductor layer 25a may have a relatively high carrier concentration. The thickness (film thickness) of the semiconductor layer 25a may be, for example, 10 nm or less.

[0071] The imaging device 1 may be configured so that the difference between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25 a is relatively small. For example, the difference φ1 between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25 a is smaller than the difference φ2 between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25 b.

[0072] In the imaging device 1, the semiconductor layers 25a and 25b may be provided so as to satisfy φ1<φ2. For example, the semiconductor layers 25a and 25b may be formed so as to satisfy φ2-φ1>0.02 eV. The semiconductor layers 25a and 25b may be configured so that the difference φ2 between the energy level of the conduction band minimum of the semiconductor layer 25b and the Fermi level is greater than the difference φ1 between the energy level of the conduction band minimum of the semiconductor layer 25a and the Fermi level by 0.02 eV or more.

[0073] The difference between the energy level of the conduction band minimum in the semiconductor layer 25 a and the vacuum level may be larger than the difference between the energy level of the conduction band minimum in the semiconductor layer 25 b and the vacuum level. In the photoelectric conversion unit 11 c of the imaging device 1, the semiconductor layer 25 a and the semiconductor layer 25 b may be provided in contact with each other with band bending.

[0074] The semiconductor layer 25 a and the semiconductor layer 25 b are formed using, for example, an oxide semiconductor material, and each of the semiconductor layer 25 a and the semiconductor layer 25 b is an oxide semiconductor layer containing at least one of In (indium), Ga (gallium), Zn (zinc), Ti (titanium), Sn (tin), Si (silicon), Cu (copper), Sb (antimony), and Cd (cadmium).

[0075] As an example, the semiconductor layer 25a and the semiconductor layer 25b are made of IGZO (indium gallium zinc oxide). The semiconductor layer 25a and the semiconductor layer 25b may be made of the same material or different materials. Each of the semiconductor layers 25a and 25b may be made by stacking multiple films. The material of the semiconductor layer 25a can be selected depending on, for example, the material of the photoelectric conversion film 22, the material of the semiconductor layer 25b, the electron affinity, the work function, the carriers (signal charges), etc.

[0076] As described above, the semiconductor layer 25a and the semiconductor layer 25b may each be an oxide semiconductor layer containing indium (In). The In composition ratio in the semiconductor layer 25a may be higher than the In composition ratio in the semiconductor layer 25b. By increasing the In composition ratio in the semiconductor layer 25a, it is possible to increase the carrier concentration N1 of the semiconductor layer 25a.

[0077] The carrier concentration can be measured by, for example, spreading resistance measurement, scanning capacitance microscopy, etc. Furthermore, the energy level, work function, etc. can be measured and analyzed by XPS (X-ray photoelectron spectroscopy), UPS (ultraviolet photoelectron spectroscopy), Kelvin probe method, etc.

[0078] The readout electrode 24 is electrically connected to the semiconductor layers 25 a and 25 b. The readout electrode 24 is provided, for example, so as to be in contact with the semiconductor layer 25 b. In the example shown in FIG. 3 , the readout electrode 24 is in contact with the semiconductor layer 25 b at an opening 85 (hole) provided in the insulating layer 131. The readout electrode 24 is an electrode used to read out the charges converted by the photoelectric conversion film 22.

[0079] The storage electrode 26 is disposed below the semiconductor layer 25b via a portion of the insulating layer 131. In the example shown in Fig. 3, the storage electrode 26 is disposed to face the upper electrode 23, with the portion of the insulating layer 131, the semiconductor layers 25a and 25b, the protective layer 29, and the photoelectric conversion film 22 sandwiched therebetween. The storage electrode 26 is an electrode used to control the accumulation of charges converted by the photoelectric conversion film 22.

[0080] In the imaging device 1, charges photoelectrically converted in the photoelectric conversion film 22 can be attracted toward the semiconductor layer 25 a and the semiconductor layer 25 b in accordance with the potential of the storage electrode 26 of each pixel P. For example, the vertical drive circuit 111 (see FIG. 1 ) of the imaging device 1 can accumulate signal charges (e.g., electrons) generated in the photoelectric conversion film 22 in a region of the semiconductor layer 25 b facing the storage electrode 26 by controlling the voltages (voltages VOU and VOA in FIG. 4 ) supplied to the upper electrode 23 and the storage electrode 26.

[0081] Furthermore, by changing the voltage (voltage VOA in FIG. 4 ) applied to the storage electrode 26, the charges stored in the semiconductor layers 25 a and 25 b can be moved toward the readout electrode 24. The vertical drive circuit 111 can, for example, adjust the voltage VOA input to the storage electrode 26 to transfer the charges stored after photoelectric conversion to the readout electrode 24.

[0082] The above-described upper electrode 23, readout electrode 24, and storage electrode 26 are each, for example, a transparent electrode and may be made of ITO (indium tin oxide), IZO (indium zinc oxide), tin oxide (SnO), zinc oxide (ZnO), etc. The upper electrode 23, readout electrode 24, and storage electrode 26 may be made of other metal oxides or other transparent conductive materials.

[0083] The top electrode 23, the readout electrode 24, and the storage electrode 26 may be formed using a tin oxide-based material such as antimony (Sb)-doped tin oxide (ATO) or fluorine (F)-doped tin oxide (FTO). The top electrode 23, the readout electrode 24, and the storage electrode 26 may be formed using a zinc oxide-based material.

[0084] The upper electrode 23, the readout electrode 24, and the storage electrode 26 may be made of, for example, aluminum zinc oxide (AZO), gallium zinc oxide (GZO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), etc. The upper electrode 23, the readout electrode 24, and the storage electrode 26 may be made of, for example, CuI, InSbO ４ , ZnMgO, CuInO ２ , MgIN ２ O４ , CdO, ZnSnO ３ , TiO ２ , spinel oxide, YbFe ２ O ４ It may be formed using an oxide having a structure.

[0085] When transparency is not required, the upper electrode 23, the readout electrode 24, or the storage electrode 26 may be made of, for example, an alkali metal (lithium (Li), sodium (Na), potassium (K), etc.), an alkaline earth metal (magnesium (Mg), calcium (Ca), etc.), etc. Alternatively, the upper electrode 23, the readout electrode 24, or the storage electrode 26 may be made of a metal material such as platinum (Pt), gold (Au), palladium (Pd), chromium (Cr), nickel (Ni), aluminum (Al), silver (Ag), tantalum (Ta), tungsten (W), copper (Cu), titanium (Ti), indium (In), tin (Sn), iron (Fe), cobalt (Co), or molybdenum (Mo).

[0086] The electrodes provided for the photoelectric conversion unit 11c, such as the upper electrode 23, the readout electrode 24, and the storage electrode 26, may be made of a conductive material such as impurity-containing polysilicon, a carbon-based material, an oxide semiconductor, a carbon nanotube, graphene, etc. Furthermore, the upper electrode 23, the readout electrode 24, the storage electrode 26, etc. may be made of an organic material (conductive polymer) such as poly(3,4-ethylenedioxythiophene) / polystyrene sulfonic acid [PEDOT / PSS].

[0087] The photoelectric conversion film 22 may absorb, for example, 60% or more of light of a predetermined wavelength included at least in the visible light range to the near-infrared range, and perform charge separation. The photoelectric conversion film 22 may, for example, absorb light of some or all wavelengths in the visible light range (400 nm or more and less than 1300 nm) and the near-infrared range. The photoelectric conversion film 22 may, for example, be composed of two or more organic materials that function as p-type or n-type semiconductors, and have a junction interface (p / n junction interface) between the p-type and n-type semiconductors. Alternatively, the photoelectric conversion film 22 may have a stacked structure (p-type semiconductor layer / n-type semiconductor layer) of a layer made of a p-type semiconductor (p-type semiconductor layer) and a layer made of an n-type semiconductor (n-type semiconductor layer), a stacked structure (p-type semiconductor layer / bulk hetero layer) of a p-type semiconductor layer and a mixed layer (bulk hetero layer) of p-type and n-type semiconductors, or a stacked structure (n-type semiconductor layer / bulk hetero layer) of an n-type semiconductor layer and a bulk hetero layer. The photoelectric conversion film 22 may also be formed solely from a mixed layer (bulk hetero layer) of p-type and n-type semiconductors.

[0088] For example, a p-type semiconductor is a hole transport material that functions relatively as an electron donor, and an n-type semiconductor is an electron transport material that functions relatively as an electron acceptor. For example, the photoelectric conversion film 22 provides a field where excitons (electron-hole pairs) generated upon light absorption separate into electrons and holes. Specifically, the electron-hole pairs separate into electrons and holes at the interface (p / n junction) between the electron donor and electron acceptor.

[0089] Examples of p-type semiconductors include naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, pentacene derivatives, quinacridone derivatives, thiophene derivatives, thienothiophene derivatives, benzothiophene derivatives, benzothienobenzothiophene (BTBT) derivatives, dinaphthothienothiophene (DNTT) derivatives, dianthracenothienothiophene (DATT) derivatives, benzobisbenzothiophene (BBBT) derivatives, thienothiophene derivatives, benzothienobenzothiophene (BTBT) derivatives, dibenzothienothiophene (DNTT) derivatives, dianthracenothienothiophene (DATT) derivatives, benzobisbenzothiophene (BBBT) derivatives, and thienothiophene derivatives. Examples of p-type semiconductors include thienoacene-based materials such as dibenzothienobisbenzothiophene (TBBT) derivatives, dibenzothienobisbenzothiophene (DBTBT) derivatives, dithienobenzodithiophene (DTBDT) derivatives, dibenzothienodithiophene (DBTDT) derivatives, benzodithiophene (BDT) derivatives, naphthodithiophene (NDT) derivatives, anthracenodithiophene (ADT) derivatives, tetracenodithiophene (TDT) derivatives, and pentacenodithiophene (PDT) derivatives. Examples of p-type semiconductors include triphenylamine derivatives, carbazole derivatives, picene derivatives, chrysene derivatives, fluoranthene derivatives, phthalocyanine derivatives, subphthalocyanine derivatives, subporphyrazine derivatives, metal complexes having heterocyclic compounds as ligands, polythiophene derivatives, polybenzothiadiazole derivatives, and polyfluorene derivatives.

[0090] As an n-type semiconductor, for example, fullerene C ６０ , fullerene C ７０ , fullerene C ７４Examples of the substituents contained in the fullerene derivatives include fullerenes and their derivatives, such as higher fullerenes and endohedral fullerenes. Examples of the substituents contained in the fullerene derivatives include halogen atoms, linear, branched, or cyclic alkyl groups or phenyl groups, groups having linear or condensed aromatic compounds, groups having halides, partial fluoroalkyl groups, perfluoroalkyl groups, silyl alkyl groups, silyl alkoxy groups, aryl silyl groups, aryl sulfanyl groups, alkyl sulfanyl groups, aryl sulfonyl groups, alkyl sulfonyl groups, aryl sulfide groups, alkyl sulfide groups, amino groups, alkyl amino groups, aryl amino groups, hydroxy groups, alkoxy groups, acyl amino groups, acyloxy groups, carbonyl groups, carboxy groups, carboxamido groups, carboalkoxy groups, acyl groups, sulfonyl groups, cyano groups, nitro groups, groups having chalcogenides, phosphine groups, phosphonic groups, and derivatives thereof. Specific examples of the fullerene derivatives include fullerene fluorides, PCBM fullerene compounds, and fullerene polymers. Other examples of n-type semiconductors include organic semiconductors that have higher HOMO levels and LUMO levels than p-type semiconductors, and inorganic metal oxides that are optically transparent.

[0091] As n-type organic semiconductor, for example, can be mentioned heterocyclic compound containing nitrogen atom, oxygen atom or sulfur atom.Specifically, for example, can be mentioned pyridine derivative, pyrazine derivative, pyrimidine derivative, triazine derivative, quinoline derivative, quinoxaline derivative, isoquinoline derivative, acridine derivative, phenazine derivative, phenanthroline derivative, tetrazole derivative, pyrazole derivative, imidazole derivative, thiazole derivative, oxazole derivative, imidazole derivative, benzimidazole derivative, benzotriazole derivative, benzoxazole derivative, carbazole derivative, benzofuran derivative, dibenzofuran derivative, subporphyrazine derivative, polyphenylenevinylene derivative, polybenzothiadiazole derivative, polyfluorene derivative, etc., organic molecule, organometallic complex, subphthalocyanine derivative, quinacridone derivative, cyanine derivative and merocyanine derivative that have in part of molecular skeleton thereof.

[0092] In addition to the p-type and n-type semiconductors, the photoelectric conversion film 22 may further include an organic material, a so-called dye material, that absorbs light in a predetermined wavelength range while transmitting light in other wavelength ranges. When the photoelectric conversion film 22 is formed using three types of organic materials, i.e., a p-type semiconductor, an n-type semiconductor, and a dye material, the p-type and n-type semiconductors may be materials that are optically transparent in the visible light range. This allows the photoelectric conversion film 22 to selectively convert light in the wavelength range absorbed by the dye material.

[0093] As shown in Fig. 3 , the imaging device 1 has a through electrode 50. The through electrode 50 is a connection electrode (connection portion) that connects circuits (elements) provided on different layers. As an example, the through electrode 50 is provided on the layer 101 so as to penetrate the semiconductor layer 110. The through electrode 50 is a structure provided within the semiconductor layer 110 so as to penetrate the semiconductor layer 110.

[0094] In the imaging device 1, a through electrode 50 is provided for each pixel P or for each set of pixels P. For example, the through electrode 50 is formed so as to extend from below the photoelectric conversion unit 11c to the surface 11S2 of the semiconductor layer 110. In the example shown in FIG. 3 , the through electrode 50 is formed so as to extend in the Z-axis direction and reach the inside of the wiring layer 120.

[0095] In the imaging device 1, the through electrode 50 electrically connects the readout electrode 24 of the photoelectric conversion unit 11c to a circuit provided on the surface 11S2 side of the semiconductor layer 110. The readout electrode 24 of the photoelectric conversion unit 11c is electrically connected to the readout circuit 15c (see FIG. 4) via the through electrode 50.

[0096] The electric charges photoelectrically converted and stored in the photoelectric conversion unit 11c are transferred by the readout electrode 24 to the floating diffusion FD3 of the readout circuit 15c via the through electrode 50. The floating diffusion FD3 stores the transferred electric charges.

[0097] The through electrodes 50 are made of, for example, tungsten (W), aluminum (Al), copper (Cu), silver (Ag), etc. The through electrodes 50 may also be made of cobalt (Co), molybdenum (Mo), ruthenium (Ru), etc. The through electrodes 50 may also be made of other metal materials.

[0098] The imaging device 1 may have at least one of a fixed charge film 55 and an antireflection film 56 on the surface 11S1 side of the semiconductor layer 110. A portion of each of the fixed charge film 55 and the antireflection film 56 is provided along the side surface of the through electrode 50, for example, as shown in the example in FIG. 3. The fixed charge film 55 and the antireflection film 56 are made of, for example, a metal compound (metal oxide, metal nitride, etc.).

[0099] The fixed charge film 55 is a film having a fixed charge and can be formed using a high dielectric material. For example, the fixed charge film 55 is made of a metal oxide such as hafnium oxide, aluminum oxide, tantalum oxide, titanium oxide, or zirconium oxide. The fixed charge film 55 is, for example, a film having a negative fixed charge.

[0100] In the imaging device 1, the fixed charge film 55 is provided to suppress the generation of dark current at the interface of the semiconductor layer 110. The fixed charge film 55 may be formed of another metal oxide film, or may be formed using a metal nitride film or a metal oxynitride film. A film having a positive fixed charge may be provided as the fixed charge film 55.

[0101] The antireflection film 56 is made of, for example, a metal oxide such as hafnium oxide or tantalum oxide. The antireflection film 56 is provided on the surface 11S1 side of the semiconductor layer 110 and reduces (suppresses) reflection. The antireflection film 56 (antireflection film) is provided, for example, so as to be stacked with the fixed charge film 55. The antireflection film 56 may be made of an insulating material such as silicon nitride (SiN), silicon oxide (SiO), silicon oxynitride (SiON), TEOS, or aluminum oxide (AlO), or may be made of other materials.

[0102] The imaging device 1 is provided with a readout circuit configured to be able to output a signal based on the charges converted by the photoelectric conversion unit 11 a, a signal based on the charges converted by the photoelectric conversion unit 11 b, and a signal based on the charges converted by the photoelectric conversion unit 11 c. The imaging device 1 has a plurality of readout circuits 15, each of which includes, for example, an amplification transistor, a selection transistor, a reset transistor, etc.

[0103] As an example, a plurality of readout circuits 15 (readout circuits 15a, 15b, and 15c in FIG. 4 ) are provided for each pixel P or for each set of multiple pixels P. Note that the imaging device 1 may have a configuration in which multiple pixels P share the readout circuit 15.

[0104] 4, the pixel P of the imaging device 1 includes the above-described photoelectric conversion unit 11a, transfer transistor TR1, and readout circuit 15a. The pixel P also includes a photoelectric conversion unit 11b, transfer transistor TR2, readout circuit 15b, photoelectric conversion unit 11c, and readout circuit 15c. The readout circuits 15a, 15b, and 15c are each configured to be able to output a signal based on the photoelectrically converted charge.

[0105] The readout circuit 15a includes, for example, a floating diffusion FD1, an amplification transistor AMP1, a selection transistor SEL1, and a reset transistor RST1. The readout circuit 15a is configured to be able to read out a signal (first pixel signal) based on the charge accumulated in the floating diffusion FD1 to a signal line VSL1. The readout circuit 15a may also include a transfer transistor TR1.

[0106] The transfer transistor TR1, the amplification transistor AMP1, the selection transistor SEL1, and the reset transistor RST1 are each a MOS transistor (MOSFET) having a gate, a source, and a drain terminal. In the example shown in Figure 4, the transfer transistor TR1, the amplification transistor AMP1, the selection transistor SEL1, and the reset transistor RST1 are each composed of an NMOS transistor. Note that the transistor of the pixel P may also be composed of a PMOS transistor.

[0107] The transfer transistor TR1 is configured to be able to transfer charges photoelectrically converted by the photoelectric conversion unit 11 a. The transfer transistor TR1 is controlled by a signal STR1 to electrically connect or disconnect the photoelectric conversion unit 11 a and the floating diffusion FD1. The transfer transistor TR1 can transfer the charges photoelectrically converted and stored in the photoelectric conversion unit 11 a to the floating diffusion FD1.

[0108] The floating diffusion FD1 is an accumulation unit configured to be able to accumulate transferred charges. The floating diffusion FD1 can accumulate charges photoelectrically converted by the photoelectric conversion unit 11a. The floating diffusion FD1 can also be considered a holding unit capable of holding the transferred charges. The floating diffusion FD1 accumulates the transferred charges and converts them into a voltage according to the capacitance of the floating diffusion FD1.

[0109] The amplifier transistor AMP1 is configured to generate and output a signal based on the charge accumulated in the floating diffusion FD1. As shown in Fig. 4, the gate of the amplifier transistor AMP1 is electrically connected to the floating diffusion FD1, and receives the voltage converted by the floating diffusion FD1.

[0110] The drain of the amplifier transistor AMP1 is connected to a power supply line to which a power supply voltage VDD is supplied. The source of the amplifier transistor AMP1 is connected to a signal line VSL1 via a selection transistor SEL1. The amplifier transistor AMP1 can generate a signal based on the charge accumulated in the floating diffusion FD1, i.e., a signal based on the voltage of the floating diffusion FD1, and output the signal to the signal line VSL1.

[0111] The selection transistor SEL1 is configured to be able to control the output of a pixel signal. The selection transistor SEL1 is electrically connected in series to the amplification transistor AMP1, for example, as shown in the example of FIG. 4. The selection transistor SEL1 is configured to be controlled by a signal SSEL1 and to be able to output a signal from the amplification transistor AMP1 to a signal line VSL1. The selection transistor SEL1 can control the output timing of the pixel signal.

[0112] The selection transistor SEL1 is configured to be able to output a signal (first pixel signal) based on the charge converted by the photoelectric conversion unit 11a. The selection transistor SEL1 can output the first pixel signal of the pixel P to a signal line VSL1. The selection transistor SEL1 may be electrically connected between a power supply line to which a power supply voltage VDD is applied and the amplification transistor AMP1. The selection transistor SEL1 may also be omitted as necessary.

[0113] The reset transistor RST1 is configured to be able to reset the voltage of the floating diffusion FD1. In the example shown in Figure 4, the reset transistor RST1 is electrically connected to a power supply line to which a power supply voltage VDD is applied and configured to reset the charge. The reset transistor RST1 is controlled by a signal SRST1 and can reset the charge accumulated in the floating diffusion FD1 and reset the voltage of the floating diffusion FD1.

[0114] The reset transistor RST1 electrically connects the power supply line and the floating diffusion FD1, and can discharge the charge accumulated in the floating diffusion FD1. The reset transistor RST1 can also discharge the charge accumulated in the photoelectric conversion unit 11 a via the transfer transistor TR1.

[0115] The vertical drive circuit 111 (see Figure 1) of the imaging device 1 supplies control signals to the gates of the transfer transistor TR1, selection transistor SEL1, reset transistor RST1, etc. of each pixel P via the above-mentioned control line Lread, turning the transistors on (conducting state) or off (non-conducting state).

[0116] The multiple control lines Lread for each pixel row of the imaging device 1 include, for example, a wiring for transmitting a signal STR1 that controls the transfer transistor TR1, a wiring for transmitting a signal SSEL1 that controls the selection transistor SEL1, and a wiring for transmitting a signal SRST1 that controls the reset transistor RST1.

[0117] The transfer transistor TR1, selection transistor SEL1, reset transistor RST1, etc. are on / off controlled by a vertical drive circuit 111. The vertical drive circuit 111 controls the readout circuit 15a of each pixel P to output a first pixel signal based on the charge generated in the photoelectric conversion unit 11a from each pixel P to a signal line VSL1. The vertical drive circuit 111 can control the reading out of the first pixel signal of each pixel P to the signal line VSL1.

[0118] The readout circuit 15 a may be configured to change the conversion efficiency (gain) when converting electric charge into voltage. For example, the readout circuit 15 a may include a switching transistor used to set the conversion efficiency. As an example, the switching transistor is provided between the floating diffusion FD1 and the reset transistor RST1.

[0119] The switching transistor may be electrically connected in series to the reset transistor RST1 or may be electrically connected in parallel to the reset transistor RST1. For example, the switching transistor may be configured to be able to electrically connect the floating diffusion FD1 and the capacitive element.

[0120] In the readout circuit 15a, when the switching transistor is turned on, the capacitance added to the floating diffusion FD1 of the pixel P increases, and the conversion efficiency is switched. The switching transistor can change the capacitance connected to the gate of the amplification transistor AMP1, thereby changing the conversion efficiency.

[0121] The readout circuit 15b has, for example, the same circuit configuration as the readout circuit 15a. The floating diffusion FD2 of the readout circuit 15b corresponds to the floating diffusion FD1 of the readout circuit 15a. The transfer transistor TR2 can transfer charges photoelectrically converted by the photoelectric conversion unit 11b to the floating diffusion FD2. The floating diffusion FD2 can accumulate the charges photoelectrically converted by the photoelectric conversion unit 11b. The readout circuit 15b may include the transfer transistor TR2.

[0122] The amplification transistor AMP2 in the readout circuit 15b corresponds to the amplification transistor AMP1 in the readout circuit 15a. The selection transistor SEL2 corresponds to the selection transistor SEL1. The reset transistor RST2 corresponds to the reset transistor RST1. The readout circuit 15b can generate and output a signal based on the charges accumulated in the floating diffusion FD2, i.e., a signal (second pixel signal) based on the charges converted by the photoelectric conversion unit 11b.

[0123] The transfer transistor TR2, selection transistor SEL2, reset transistor RST2, etc. are on / off controlled by a vertical drive circuit 111. The vertical drive circuit 111 controls the readout circuit 15b of each pixel P to output a second pixel signal based on the charge generated in the photoelectric conversion unit 11b from each pixel P to a signal line VSL2. The vertical drive circuit 111 can control the reading out of the second pixel signal of each pixel P to the signal line VSL2.

[0124] The readout circuit 15c has, for example, the same circuit configuration as the readout circuit 15a. The floating diffusion FD3 in the readout circuit 15c corresponds to the floating diffusion FD1 in the readout circuit 15a. The amplification transistor AMP3 in the readout circuit 15c corresponds to the amplification transistor AMP1 in the readout circuit 15a.

[0125] The select transistor SEL3 corresponds to the select transistor SEL1. The reset transistor RST3 corresponds to the reset transistor RST1. The readout circuit 15c can generate and output a signal based on the charges accumulated in the floating diffusion FD3, i.e., a signal (third pixel signal) based on the charges converted by the photoelectric conversion unit 11c.

[0126] The photoelectric conversion unit 11c is electrically connected to the readout circuit 15c via the above-described through electrode 50. The readout electrode 24 of the photoelectric conversion unit 11c is connected to the floating diffusion FD3 via the through electrode 50. Charges photoelectrically converted by the photoelectric conversion unit 11c can be transferred from the photoelectric conversion unit 11c to the floating diffusion FD3 via the through electrode 50.

[0127] The selection transistor SEL3, reset transistor RST3, etc. are on / off controlled by a vertical drive circuit 111. The vertical drive circuit 111 controls the storage electrode 26, readout circuit 15c, etc. of each pixel P to output a third pixel signal based on the charge generated in the photoelectric conversion unit 11c from each pixel P to a signal line VSL3. The vertical drive circuit 111 can control the reading out of the third pixel signal of each pixel P to the signal line VSL3.

[0128] 3, light from a subject to be measured is incident on the photoelectric conversion unit 11c, the photoelectric conversion unit 11b, and the photoelectric conversion unit 11a of pixel P via a lens 81. The photoelectric conversion unit 11c can generate electric charges by photoelectrically converting the light incident via the lens 81. For example, light that has passed through the photoelectric conversion unit 11c is incident on the photoelectric conversion unit 11b of pixel P. In the example shown in FIG. 3, light that has passed through the lens 81 and the photoelectric conversion unit 11c is incident on the photoelectric conversion unit 11b.

[0129] The photoelectric conversion unit 11b can generate charges by photoelectrically converting light that passes through the photoelectric conversion unit 11c. For example, light that has passed through the photoelectric conversion unit 11b is incident on the photoelectric conversion unit 11a of the pixel P. In the example shown in FIG. 3, light that has passed through the lens 81, the photoelectric conversion unit 11c, and the photoelectric conversion unit 11b is incident on the photoelectric conversion unit 11a. The photoelectric conversion unit 11a can generate charges by photoelectrically converting light that passes through the photoelectric conversion unit 11b.

[0130] The imaging device 1 can obtain a first pixel signal based on the charges converted by the photoelectric conversion unit 11 a, a second pixel signal based on the charges converted by the photoelectric conversion unit 11 b, and a third pixel signal based on the charges converted by the photoelectric conversion unit 11 c. Each of the photoelectric conversion units 11 a, 11 b, and 11 c may be configured to receive visible light and perform photoelectric conversion, or may be configured to receive infrared light (e.g., near-infrared light) and perform photoelectric conversion.

[0131] For example, the photoelectric conversion units 11a, 11b, and 11c may be configured to generate charges by photoelectrically converting visible light in different wavelength ranges. Furthermore, for example, the photoelectric conversion unit 11a or the photoelectric conversion unit 11b may be configured to generate charges by photoelectrically converting infrared light. By using the first pixel signal, the second pixel signal, and the third pixel signal of each pixel P, it is possible to generate a visible image (e.g., an RGB image), an infrared image (IR image), or the like.

[0132] As an example, the photoelectric conversion unit 11c of pixel P receives and photoelectrically converts light mainly in the green (G) wavelength range from light from the subject to be measured. The photoelectric conversion unit 11b receives and photoelectrically converts light mainly in the blue (B) wavelength range. Furthermore, the photoelectric conversion unit 11a receives and photoelectrically converts light mainly in the red (R) wavelength range.

[0133] Each pixel P of the imaging device 1 can generate an R component pixel signal, a G component pixel signal, and a B component pixel signal. The imaging device 1 can obtain RGB pixel signals. Note that the wavelength ranges to which the photoelectric conversion units 11a, 11b, and 11c are each sensitive can be set arbitrarily.

[0134] 5 is a diagram illustrating an example of the planar configuration of the imaging device according to the first embodiment. The imaging device 1 may have a configuration in which an arbitrary number (for example, four) of pixels P arranged in a row direction (horizontal direction) or a column direction (vertical direction) share the readout electrode 24, the readout circuit 15, etc.

[0135] Fig. 5 shows an example in which the photoelectric conversion units 11c of four adjacent pixels P share one readout electrode 24. In the example shown in Fig. 5, the imaging device 1 has a configuration in which the photoelectric conversion units 11c of four pixels P, which are 2 × 2 pixels, share the readout electrode 24 and the readout circuit 15c.

[0136] The readout electrode 24 is provided for four adjacent photoelectric conversion units 11c. For example, at least a portion of the readout electrode 24 is provided on the boundary between the four pixels P. In the example shown in Fig. 5, the readout electrode 24 is disposed in the central region of the four pixels P. The storage electrode 26 is provided for each photoelectric conversion unit 11c, for example.

[0137] The imaging device 1 may also have a shield electrode 27, as in the example shown in Fig. 5. The shield electrode 27 is provided around the storage electrode 26 in the insulating layer 131 (see also Fig. 6 described later). The shield electrode 27 is provided for the photoelectric conversion film 22 for each pixel P or for each set of multiple pixels P. A predetermined potential (voltage) is supplied to the shield electrode 27 via, for example, wiring, electrodes, etc.

[0138] For example, the shield electrode 27 is electrically connected to a wiring to which a constant voltage is applied, and can generate a potential barrier in the semiconductor layer 25 b. The provision of the shield electrode 27 prevents the charge photoelectrically converted in the photoelectric conversion unit 11 c of the pixel P from leaking to surrounding pixels P.

[0139] The shield electrode 27 is, for example, a transparent electrode and is made of a material that transmits light that is photoelectrically converted in the photoelectric conversion unit. For example, the shield electrode 27 is made of ITO, IZO, or the like. The shield electrode 27 may be formed of other tin oxide-based materials, zinc oxide-based materials, or the like, or may be made of other transparent conductive materials. The shield electrode 27 may be made of, for example, the same type of material as the readout electrode 24, the storage electrode 26, and the like.

[0140] Fig. 6 is a diagram for explaining an example of the configuration of the imaging device according to the first embodiment. Fig. 7 is a diagram showing an example of energy levels in the imaging device according to the first embodiment. Fig. 7 shows the energy levels of the upper electrode 23, the photoelectric conversion film 22, the protective layer 29, the semiconductor layer 25a, the semiconductor layer 25b, and the storage electrode 26.

[0141] 3, 6, etc., the imaging device 1 according to the present embodiment is provided with a semiconductor layer 25a. The semiconductor layer 25a has a carrier concentration higher than that of the semiconductor layer 25b, for example, as described above. This allows the interface state of the photoelectric conversion film 22 to be filled with charges (electrons), making it possible to prevent noise caused by the interface state of the photoelectric conversion film 22 from being mixed into pixel signals.

[0142] In the imaging device 1, the semiconductor layer 25a having a high carrier concentration can fill electrons in the interface state between the protective layer 29 and the semiconductor layer 25a, as schematically represented by an "X" mark in Fig. 7. This can prevent signal charges (electrons) photoelectrically converted in the photoelectric conversion film 22 from being trapped (captured) in the interface state between the protective layer 29 and the semiconductor layer 25a.

[0143] In the imaging device 1, the provision of the semiconductor layer 25 a makes it possible to reduce noise caused by interface states, for example, noise components caused by electrons emitted late from the interface states, thereby suppressing deterioration in the quality of pixel signals (the above-described third pixel signals), and thus suppressing deterioration in the quality of images generated using the pixel signals.

[0144] Furthermore, the imaging device 1 can be configured so that the difference φ1 between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25a is smaller than the difference φ2 between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25b. Therefore, the semiconductor layers 25a and 25b can move electrons to defect levels at the interface between the protective layer 29 and the semiconductor layer 25a, thereby reducing interface levels that are not filled with electrons (i.e., vacant interface defects). This makes it possible to effectively suppress noise mixed into pixel signals.

[0145] The difference between the energy level of the conduction band minimum in the protective layer 29 and the vacuum level may be smaller than the difference between the energy level of the conduction band minimum in the semiconductor layer 25a and the vacuum level. The thickness (film thickness) of the protective layer 29 may be, for example, 5 nm or less. This can prevent an unnecessary potential barrier from being formed between the protective layer 29 and the semiconductor layer 25a. This can prevent a decrease in the transfer efficiency of charges generated in the photoelectric conversion film 22.

[0146] 8A to 8D are diagrams illustrating an example of a method for manufacturing the image pickup device according to the first embodiment. First, a readout electrode 24, a storage electrode 26, a shield electrode 27, etc. are sequentially formed on the semiconductor layer 110 on which the photoelectric conversion units 11a and 11b, etc. are formed.

[0147] 8A, a semiconductor layer 25b is formed on the insulating layer 131 by sputtering or atomic vapor deposition (ALD). For example, an IGZO film is formed as the semiconductor layer 25b. After the semiconductor layer 25b is formed, an annealing treatment (for example, 100°C to 600°C) may be performed.

[0148] Next, as shown in FIG. 8B, an Al film 90 (aluminum film) is formed on the semiconductor layer 25b by sputtering. For example, the thickness of the Al film 90 is about 5 nm. Then, by performing annealing (for example, at 300° C. to 400° C.), the semiconductor layer 25a and the Al film 90 are bonded together as shown in FIG. 8C. ２ O ３ A protective layer 29 made of the following is formed.

[0149] By forming an Al film 90 on the semiconductor layer 25b made of an IGZO film and performing annealing, it is possible to form a semiconductor layer 25a having a high carrier concentration and a protective layer 29. ２ O ３ By providing the protective layer 29 made of the above, it is possible to improve the sealing performance of the semiconductor layer 25a. In addition, it is expected that the occurrence of interface defects will be reduced.

[0150] 8D, the protective layer 29 may be removed by etching as needed. After the semiconductor layer 25a is formed, the photoelectric conversion film 22, the upper electrode 23, etc. are formed. By the manufacturing method described above, the imaging device 1 shown in FIG. 3 etc. can be manufactured.

[0151] In the imaging device 1, the constituent elements of the semiconductor layer 25a may be different from the constituent elements of the semiconductor layer 25b. For example, the semiconductor layer 25a may contain an element (e.g., aluminum in the example described above using FIGS. 8A to 8C ) different from the constituent elements of the semiconductor layer 25b.

[0152] The semiconductor layer 25a may be configured to contain the cations that make up the protective layer 29. For example, the protective layer 29 may be Al ２ O ３ When the semiconductor layer 25a is made of the above, the semiconductor layer 25a can be made to contain aluminum as cations that penetrate from the Al film 90 during annealing.

[0153] It should be noted that the above-described manufacturing method is merely an example, and other manufacturing methods may be adopted. Furthermore, the configuration of the imaging device 1 is not limited to the above-described example. Instead of the Al film 90, a film of Ga (gallium), In (indium), Sc (scandium), Y (yttrium), or the like may be formed on the semiconductor layer 25b, and the semiconductor layer 25a may be formed by annealing.

[0154] Alternatively, the semiconductor layer 25a may be formed by the ALD method. For example, the semiconductor layer 25a may be formed by the ALD method using ZnO and Al. ２ O ３ The semiconductor layer 25a and the semiconductor layer 25b may be formed as a laminated film by laminating Si-doped Ga ２ O３ , Al-doped ZnO, Ga-doped ZnO, or the like.

[0155] Fig. 9 is a diagram for explaining another example configuration of the imaging device according to the first embodiment. The imaging device 1 does not need to have the protective layer 29, as in the example shown in Fig. 9. Fig. 10 is a diagram showing an example of energy levels in the imaging device. Fig. 10 shows the energy levels of the upper electrode 23, the photoelectric conversion film 22, the semiconductor layer 25a, the semiconductor layer 25b, and the storage electrode 26, respectively. The semiconductor layer 25a is provided in contact with the photoelectric conversion film 22, for example.

[0156] In the imaging device 1, by providing the semiconductor layer 25a having a high carrier concentration, it is possible to fill electrons in the interface state between the photoelectric conversion film 22 and the semiconductor layer 25a, as schematically represented by an "X" mark in Fig. 10. This makes it possible to prevent signal charges (electrons) photoelectrically converted by the photoelectric conversion film 22 from being trapped in the interface state between the photoelectric conversion film 22 and the semiconductor layer 25a. This makes it possible to prevent noise caused by the interface state from being mixed into pixel signals.

[0157] Furthermore, the difference φ1 between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25a may be smaller than the difference φ2 between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25b. The semiconductor layers 25a and 25b allow electrons to move to the interface state between the photoelectric conversion film 22 and the semiconductor layer 25a, thereby reducing interface states that are not filled with electrons (vacant interface defects). This makes it possible to effectively suppress noise mixed into pixel signals. This makes it possible to suppress degradation of image quality.

[0158] 11 is a timing chart showing an example of the operation of the imaging device according to the first embodiment. The timing chart shown in Fig. 11, with time on the horizontal axis, schematically shows the voltage of the storage electrode 26 of the pixel P, the voltage of the floating diffusion FD3 (referred to as voltage VFD), and the voltage of the signal SRST3 supplied to the reset transistor RST3.

[0159] 11 , the vertical drive circuit 111 applies a potential V1 to the readout electrode 24 and a potential V2 to the storage electrode 26. Here, the potentials V1 and V2 satisfy the relationship V2>V1. As a result, the charge (signal charge; electrons) generated by photoelectric conversion is attracted to the storage electrode 26 and stored in the region of the semiconductor layer 25b facing the storage electrode 26 (storage period).

[0160] At time t1, the vertical drive circuit 111 changes the voltage of the signal SRST3 from low to high, which turns on the reset transistor RST3 in the pixel P and resets the voltage of the floating diffusion FD3 (reset period).

[0161] At time t2, the vertical drive circuit 111 applies a potential V3 to the readout electrode 24 and a potential V4 to the storage electrode 26. Here, the potentials V3 and V4 satisfy V3>V4. As a result, the charge stored in the region corresponding to the storage electrode 26 is read out from the readout electrode 24 to the floating diffusion FD3 (transfer period).

[0162] After the read operation is completed, the vertical drive circuit 111 again applies potential V1 to the read electrode 24 and potential V2 to the storage electrode 26. As a result, the charge generated by photoelectric conversion is attracted to the storage electrode 26 and stored in the region of the semiconductor layer 25b facing the storage electrode 26 (storage period).

[0163] In the imaging device 1, for example, of the light transmitted through the photoelectric conversion unit 11c, blue light (B) is absorbed and photoelectrically converted in the photoelectric conversion unit 11b, and red light (R) is absorbed and photoelectrically converted in the photoelectric conversion unit 11a. In the photoelectric conversion unit 11b, electrons corresponding to the incident blue light (B) are accumulated in the photoelectric conversion unit 11b, and the accumulated electrons are transferred to the floating diffusion FD2 by the transfer transistor TR2. In the photoelectric conversion unit 11a, electrons corresponding to the incident red light (R) are accumulated in the photoelectric conversion unit 11a, and the accumulated electrons are transferred to the floating diffusion FD1 by the transfer transistor TR1.

[0164] [Functions and Effects] The photodetector according to this embodiment includes a first electrode (e.g., upper electrode 23), a second electrode (e.g., storage electrode 26) provided so as to face the first electrode, a photoelectric conversion film (photoelectric conversion film 22) provided between the first electrode and the second electrode, a first semiconductor layer (semiconductor layer 25 a) provided between the photoelectric conversion film and the second electrode, and a second semiconductor layer (semiconductor layer 25 b) provided between the first semiconductor layer and the second electrode. The difference between the energy level of the conduction band minimum and the Fermi level in the first semiconductor layer is smaller than the difference between the energy level of the conduction band minimum and the Fermi level in the second semiconductor layer.

[0165] In the photodetector (image capture device 1) according to this embodiment, the difference between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25 a is smaller than the difference between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25 b. This makes it possible to suppress noise caused by interface states and to prevent degradation in pixel signal quality. This makes it possible to realize a photodetector that can prevent degradation in signal quality.

[0166] The photodetector according to this embodiment includes a first electrode (e.g., upper electrode 23), a second electrode (e.g., storage electrode 26) disposed opposite the first electrode, a photoelectric conversion film (photoelectric conversion film 22) disposed between the first electrode and the second electrode, a first semiconductor layer (semiconductor layer 25a) disposed between the photoelectric conversion film and the second electrode, and a second semiconductor layer (semiconductor layer 25b) disposed between the first semiconductor layer and the second electrode. The carrier concentration in the first semiconductor layer is higher than the carrier concentration in the second semiconductor layer.

[0167] The photodetector (image capture device 1) according to this embodiment includes a semiconductor layer 25a. The carrier concentration in the semiconductor layer 25a is higher than the carrier concentration in the semiconductor layer 25b. This makes it possible to suppress noise caused by interface states. This makes it possible to realize a photodetector that can suppress degradation of signal quality.

[0168] Next, a modified example of the present disclosure will be described. In the following, the same components as those in the above embodiment will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0169] (Variation 1) Fig. 12 is a diagram for explaining an example of a cross-sectional configuration of an imaging device according to Variation 1 of the present disclosure. Fig. 13 is a diagram for explaining an example of a planar configuration of the imaging device. As in the examples shown in Figs. 12 and 13, a semiconductor layer 25a may be provided in a region facing the storage electrode 26. As in the example shown in Fig. 13, the semiconductor layer 25a is provided so as to overlap the storage electrode 26 in a plan view.

[0170] 14 is a diagram illustrating another example configuration of the imaging device according to Modification 1. The imaging device 1 may be provided with a semiconductor layer 25c, which is different from the semiconductor layer 25b, in a peripheral region of the semiconductor layer 25a. For example, as in the example shown in FIG. 14, the semiconductor layer 25c is provided adjacent to the semiconductor layer 25a. The semiconductor layer 25a and the semiconductor layer 25c may be selectively formed by, for example, ion implantation, plasma doping, solid-phase diffusion, or the like.

[0171] 14, the semiconductor layer 25c is formed in a region facing the read electrode 24 and a region facing the shield electrode 27. The semiconductor layer 25a has, for example, a carrier concentration higher than that of the semiconductor layer 25c. The difference between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25a may be smaller than the difference between the energy level of the conduction band minimum and the Fermi level in the semiconductor layer 25c.

[0172] 15 is a diagram illustrating another example configuration of an imaging device according to Modification 1. As shown in FIG. 15, each pixel P of the imaging device 1 may have a control electrode 28. The vertical drive circuit 111 of the imaging device 1 can adjust the potential in the photoelectric conversion unit 11c, for example, by controlling the voltage supplied to the control electrode 28. In the imaging device 1, it is possible to efficiently store and transfer charges using the storage electrode 26 and the readout electrode 24.

[0173] (Modification 2) Fig. 16 is a diagram illustrating an example of a cross-sectional configuration of an imaging device according to Modification 2. Fig. 17 is a diagram illustrating an example of energy levels in the imaging device. The semiconductor layer 25a and the semiconductor layer 25b may be made of different materials. As in the example shown in Fig. 17, the energy level of the conduction band minimum in the semiconductor layer 25a may be deeper (smaller) than the energy level of the conduction band minimum in the semiconductor layer 25b.

[0174] In this modification, the semiconductor layers 25 a and 25 b can fill the interface states with electrons, thereby preventing noise caused by the interface states from being mixed into the pixel signals. This reduces the noise components mixed into the pixel signals, and prevents deterioration of the image quality.

[0175] (Modification 3) Fig. 18 is a diagram for explaining an example of the cross-sectional configuration of an imaging device according to Modification 3. Fig. 19 is a diagram showing an example of energy levels in the imaging device. The protective layer 29 may be configured as a thin tunnel layer, as in the examples schematically shown in Figs. 18 and 19. The thickness (film thickness) of the protective layer 29 may be, for example, 5 nm or less. In the case of this modification, the same effects as those of the above-described embodiment can be obtained.

[0176] 20 is a diagram illustrating a configuration example of an imaging device according to Modification 4. The semiconductor layer 25 a and the semiconductor layer 25 b may each be an oxide semiconductor layer containing zinc (Zn). When the Zn composition ratio is small (low), many Zn vacancies that capture electrons tend to be generated, as schematically shown in FIG.

[0177] Therefore, in the imaging device 1, the Zn composition ratio in the semiconductor layer 25a may be larger than the Zn composition ratio in the semiconductor layer 25b. By increasing (raising) the Zn composition ratio in the semiconductor layer 25a, the carrier concentration in the semiconductor layer 25a can be increased. Because the increase in carrier concentration is not due to defects, it is possible to improve the reliability of the device.

[0178] In the photodetector according to this modification, the first semiconductor layer and the second semiconductor layer (semiconductor layer 25a, semiconductor layer 25b) are each an oxide semiconductor layer containing Zn. The Zn composition ratio in the first semiconductor layer is higher than the Zn composition ratio in the second semiconductor layer. This makes it possible to suppress noise caused by interface states and to prevent degradation in the quality of pixel signals. It also makes it possible to improve the reliability of the device.

[0179] 21 is a diagram illustrating a configuration example of an imaging device according to Modification 5. As schematically shown in Fig. 21 , if the band gap of the semiconductor layer is large, there is a risk that many defect levels (e.g., interface levels of the photoelectric conversion film 22 or the protective layer 29) will not be filled with electrons. Therefore, the semiconductor layer 25a may be configured to have a relatively small band gap.

[0180] The band gap of the semiconductor layer 25 a may be smaller than the band gap of the semiconductor layer 25 b, for example. The semiconductor layer 25 a may be made of a material having a band gap smaller than the band gap of the semiconductor layer 25 b. By configuring the imaging device 1 in this manner, the carrier concentration in the semiconductor layer 25 a can be increased, and electrons can be filled in the defect levels, as schematically shown in FIG. 21 .

[0181] In the imaging device 1, the energy level of the conduction band minimum in the photoelectric conversion film 22 may be higher than the energy level of the conduction band minimum in the semiconductor layer 25 a. The energy level of the conduction band minimum in the semiconductor layer 25 a may be higher than the energy level of the conduction band minimum in the semiconductor layer 25 b. The imaging device 1 according to this modification can also achieve the same effects as those of the above-described embodiment.

[0182] Furthermore, the energy level of the upper end of the valence band in the protective layer 29 of the imaging device 1 may be higher than the energy level of the upper end of the valence band in the semiconductor layer 25 a. In this case, it is possible to reduce defect levels that are not filled with electrons. This makes it possible to suppress noise mixed into pixel signals and prevent degradation of image quality.

[0183] In the photodetector according to this modification, the band gap of the first semiconductor layer (semiconductor layer 25 a) is smaller than the band gap of the second semiconductor layer (semiconductor layer 25 b). This makes it possible to suppress noise caused by interface states. This makes it possible to realize a photodetector that can suppress degradation of signal quality.

[0184] (Variation 6) In the above-described embodiment and variations, exemplary configurations of the imaging device 1 have been described, but these are merely examples, and the configuration of the imaging device 1 is not limited to the above-described examples. Fig. 22 is a diagram illustrating an exemplary configuration of an imaging device according to Variation 6. As shown in Fig. 22, the imaging device 1 according to this variation has a structure in which a photoelectric conversion unit 11a, a photoelectric conversion unit 11b, and a photoelectric conversion unit 11c are stacked. From the light incident side, the photoelectric conversion unit 11c, the photoelectric conversion unit 11b, and the photoelectric conversion unit 11a are provided.

[0185] The photoelectric conversion unit 11b includes, for example, the above-described photoelectric conversion film 22, upper electrode 23, readout electrode 24, semiconductor layer 25a, semiconductor layer 25b, and storage electrode 26. The photoelectric conversion unit 11c is provided so as to be stacked on the photoelectric conversion unit 11b. The photoelectric conversion unit 11c may have the same configuration as the photoelectric conversion unit 11b.

[0186] The photoelectric conversion unit 11c includes, for example, a photoelectric conversion film 32, an upper electrode 33, a readout electrode 34, a semiconductor layer 35a, a semiconductor layer 35b, and a storage electrode 36. The photoelectric conversion film 32, the upper electrode 33, and the readout electrode 34 of the photoelectric conversion unit 11c correspond to the photoelectric conversion film 22, the upper electrode 23, and the readout electrode 24 of the photoelectric conversion unit 11b, respectively. The semiconductor layer 35a, the semiconductor layer 35b, and the storage electrode 36 of the photoelectric conversion unit 11c correspond to the semiconductor layer 25a, the semiconductor layer 25b, and the storage electrode 26 of the photoelectric conversion unit 11b, respectively.

[0187] The photoelectric conversion units 11a, 11b, and 11c are configured to selectively detect light in different wavelength ranges and perform photoelectric conversion, for example. As an example, the photoelectric conversion unit 11b acquires a pixel signal of a green (G) color component. The photoelectric conversion unit 11c acquires a pixel signal of a blue (B) color component. Furthermore, the photoelectric conversion unit 11a acquires a pixel signal of a red (R) color component. This allows the imaging device 1 to acquire multiple types of color signals from a single pixel.

[0188] 23A is a diagram illustrating another example configuration of an imaging device according to Modification Example 6. As shown in Fig. 23A, the imaging device 1 may have a structure in which a photoelectric conversion unit 11a and a photoelectric conversion unit 11c are stacked. The imaging device 1 may also be provided with a filter 57. The filter 57 is configured to selectively transmit light in a specific wavelength range from the incident light.

[0189] The filter 57 is provided, for example, between the lens 81 and the photoelectric conversion unit 11c. The filter 57 is an RGB color filter, a filter that transmits infrared light, etc. The filter 57 is provided above the photoelectric conversion unit 11c, for example, for each pixel P or for each set of pixels P (i.e., for each predetermined number of pixels P).

[0190] The plurality of pixels P provided in the pixel section 100 (see FIGS. 1 and 2 ) of the imaging device 1 include, for example, a pixel Pr (R pixel) provided with a filter 57 that transmits red (R) light, a pixel Pg (G pixel) provided with a filter 57 that transmits green (G) light, and a pixel Pb (B pixel) provided with a filter 57 that transmits blue (B) light. In the pixel section 100, the plurality of pixels Pr, the plurality of pixels Pg, and the plurality of pixels Pb are repeatedly arranged. The pixels Pr, the pixels Pg, and the pixels Pb are, for example, arranged according to a Bayer array.

[0191] The pixels Pr, Pg, and Pb of the pixel unit 100 can generate an R component pixel signal, a G component pixel signal, and a B component pixel signal, respectively. The imaging device 1 can obtain RGB pixel signals. Note that a filter 57 may be disposed between the photoelectric conversion units 11b and 11a.

[0192] In the imaging device 1, for example, light in the visible light region (red light (R), green light (G), and blue light (B)) that has passed through the filter 57 is absorbed and photoelectrically converted by the photoelectric conversion unit 11c of each pixel P. The photoelectric conversion unit 11a of each pixel P may be configured to photoelectrically convert infrared light (IR) that has passed through the photoelectric conversion unit 11c. This makes it possible to generate both visible light images and infrared light images.

[0193] 23B is a diagram illustrating another example configuration of an imaging device according to Modification Example 6. As in the example shown in FIG. 23B , the filter 57 may be provided between the photoelectric conversion unit 11c and the photoelectric conversion unit 11a (or the photoelectric conversion unit 11b). In the imaging device 1, for example, a filter 57 (filter 57R) that selectively transmits at least red light (R) and a filter 57 (filter 57B) that selectively transmits at least blue light (B) may be disposed.

[0194] The photoelectric conversion unit 11c is configured to selectively absorb light having a wavelength corresponding to, for example, green light (G). The photoelectric conversion unit 11a selectively absorbs light having a wavelength corresponding to red light (R), and the photoelectric conversion unit 11b selectively absorbs light having a wavelength corresponding to blue light (B). This makes it possible to obtain signals corresponding to red light (R), green light (G), or blue light (B). The area of ​​each photoelectric conversion unit for RGB can be enlarged compared to the case of a general Bayer array, making it possible to improve the S / N ratio.

[0195] 2. Second Embodiment Next, a second embodiment of the present disclosure will be described. In the following, components similar to those in the above-described embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0196] Fig. 24 is a diagram illustrating a configuration example of an imaging device according to a second embodiment of the present disclosure. Fig. 25 is a diagram illustrating an example of energy levels in the imaging device. The semiconductor layer 25a of the imaging device 1 is configured to have a high carrier concentration (carrier density). The semiconductor layer 25a is configured to have a carrier concentration higher (larger) than the carrier concentration of the semiconductor layer 25b, for example.

[0197] The imaging device 1 may also be configured so that the difference between the energy level of the conduction band minimum on the semiconductor layer 25a side of the photoelectric conversion film 22 and the vacuum level is larger than the difference between the energy level of the conduction band minimum on the photoelectric conversion film 22 side of the semiconductor layer 25a and the vacuum level. In the example shown in Fig. 25, the difference between the energy level E1 of the conduction band minimum on the semiconductor layer 25a side of the photoelectric conversion film 22 and the vacuum level is larger than the difference between the energy level E2 of the conduction band minimum on the photoelectric conversion film 22 side of the semiconductor layer 25a and the vacuum level.

[0198] 25, the photoelectric conversion film 22 and the semiconductor layer 25a are provided in contact with each other with band bending. By configuring the image pickup device 1 in this manner, for example, it is possible to reduce the tunnel distance between the photoelectric conversion film 22 and the semiconductor layer 25a, and to prevent a deterioration in the transfer efficiency of signal charges (e.g., electrons).

[0199] In the imaging device 1 according to the present embodiment, the band bending in the semiconductor layer 25 a can be made strong (i.e., changed sharply). This makes it possible to suppress the inhibition of electron transport and the decrease in light utilization efficiency. It also makes it possible to suppress the generation of noise due to interface states.

[0200] Fig. 26 is a diagram illustrating another example of the configuration of the imaging device according to the second embodiment. The imaging device 1 may have a protective layer 29, as in the example shown in Fig. 26. Fig. 27 is a diagram illustrating an example of energy levels in the imaging device. Fig. 27 shows the energy levels of the upper electrode 23, the photoelectric conversion film 22, the protective layer 29, the semiconductor layer 25a, the semiconductor layer 25b, and the storage electrode 26, respectively.

[0201] The protective layer 29 is, for example, a protective layer containing an inorganic material, and is provided between the photoelectric conversion film 22 and the semiconductor layer 25 a. In the example shown in Fig. 26, the protective layer 29 is formed between the photoelectric conversion film 22 and the semiconductor layer 25 a, and is located on the semiconductor layer 25 a.

[0202] In the imaging device 1, the difference between the vacuum level and the energy level of the conduction band minimum on the semiconductor layer 25a side of the protective layer 29 may be larger than the difference between the vacuum level and the energy level of the conduction band minimum on the semiconductor layer 25a side of the protective layer 29. This reduces the tunneling distance between the protective layer 29 and the semiconductor layer 25a, making it possible to suppress a decrease in the transport efficiency of charges generated in the photoelectric conversion film 22.

[0203] [Actions and Effects] In the photodetector (imaging device 1) according to this embodiment, the difference between the energy level of the conduction band minimum on the first semiconductor layer (semiconductor layer 25 a) side in the photoelectric conversion film (photoelectric conversion film 22) and the vacuum level is larger than the difference between the energy level of the conduction band minimum on the photoelectric conversion film side in the first semiconductor layer and the vacuum level.

[0204] In the photodetector (image capture device 1) according to this embodiment, the provision of the semiconductor layer 25 a can suppress a decrease in charge transport efficiency, thereby realizing a photodetector capable of suppressing a decrease in signal quality.

[0205] Next, a modified example of the present disclosure will be described. In the following, the same components as those in the above embodiment will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0206] 28A and 28B are diagrams illustrating an example of a cross-sectional configuration of an imaging device according to Modification 7 of the present disclosure. As in the example shown in FIG. 28A or 28B , a semiconductor layer 25a may be provided in a region facing the storage electrode 26. Furthermore, in the imaging device 1, a semiconductor layer 25c may be provided in a region surrounding the semiconductor layer 25a. Furthermore, the imaging device 1 may have a control electrode 28, as in the example shown in FIG. 25B .

[0207] (Variation 8) Fig. 29 is a diagram for explaining an example of a cross-sectional configuration of an imaging device according to Variation 8. The imaging device 1 may have a plurality of protective layers 29 (protective layers 29a and 29b in Fig. 29). Fig. 30 is a diagram showing an example of energy levels in the imaging device. Fig. 30 shows the energy levels of the upper electrode 23, the photoelectric conversion film 22, the protective layers 29a and 29b, the semiconductor layers 25a and 25b, and the storage electrode 26, respectively.

[0208] Each of the protective layers 29a and 29b is, for example, a protective layer containing an inorganic material, and is provided between the photoelectric conversion film 22 and the semiconductor layer 25a. The protective layers 29a and 29b each contain, for example, at least one of Ti, Si, Zr, Nb, V, Ta, Hf, Al, Sn, Sc, Y, La, Ga, and Mg.

[0209] 29 , the protective layer 29a is formed between the photoelectric conversion film 22 and the protective layer 29b, and is located on the protective layer 29b. The protective layer 29b is formed between the protective layer 29a and the semiconductor layer 25a, and is located on the semiconductor layer 25a. The protective layer 29a and the protective layer 29b may be provided so as to be stacked on top of each other. Note that the protective layer 29a and the protective layer 29b may be made of the same type of material or different materials.

[0210] In the imaging device 1, the difference between the energy level of the conduction band minimum of the protective layer 29b and the vacuum level may be smaller than the difference between the energy level of the conduction band minimum of the semiconductor layer 25a and the vacuum level. The protective layer 29b may be configured as, for example, a tunnel layer. The thickness of the protective layer 29b may be 5 nm or less. In this modified example, the same effects as those of the above-described embodiment can be obtained.

[0211] 3. Application Examples (Application Example 1) The above-described light detection device (imaging device 1) can be applied to various electronic devices, such as imaging systems such as digital still cameras and digital video cameras, mobile phones with imaging functions, and other devices with imaging functions.

[0212] FIG. 31 is a block diagram showing an example of the configuration of an electronic device.

[0213] As shown in Figure 31, electronic device 1001 is equipped with an optical system 1002, a photodetector 1003, and a DSP (Digital Signal Processor) 1004, and is configured by connecting DSP 1004, a display device 1005, an operation system 1006, a memory 1008, a recording device 1009, and a power supply system 1010 via a bus 1007, and is capable of capturing still images and moving images.

[0214] The optical system 1002 is configured to have one or more lenses, and guides image light (incident light) from a subject to the photodetector 1003 , forming an image on the light receiving surface (sensor portion) of the photodetector 1003 .

[0215] The above-described photodetector (imaging device 1) can be applied as the photodetector 1003. Electrons are accumulated in the photodetector 1003 for a certain period of time in accordance with an image formed on the light-receiving surface via the optical system 1002. A signal corresponding to the electrons accumulated in the photodetector 1003 is then supplied to the DSP 1004.

[0216] The DSP 1004 performs various signal processing on the signal from the photodetector 1003 to acquire an image, and temporarily stores the image data in a memory 1008. The image data stored in the memory 1008 is recorded in a recording device 1009 or supplied to a display device 1005 to display the image. In addition, an operation system 1006 accepts various operations by a user and supplies operation signals to each block of the electronic device 1001. A power supply system 1010 supplies the power necessary to drive each block of the electronic device 1001.

[0217] Application Example 2 Fig. 32A is a schematic diagram showing an example of the overall configuration of a light detection system 2000 including a light detection device (image capture device 1). Fig. 32B is a schematic diagram showing an example of the circuit configuration of the light detection system 2000. The light detection system 2000 includes a light emitting device 2001 as a light source unit that emits light L2, and a light detection device 2002 as a light receiving unit that has a photoelectric conversion element.

[0218] The above-described light detection device (imaging device 1) can be used as the light detection device 2002. The light detection system 2000 may further include a system control unit 2003, a light source driving unit 2004, a sensor control unit 2005, a light source side optical system 2006, and a camera side optical system 2007.

[0219] The light detection device 2002 can detect light L1 and light L2. Light L1 is external ambient light reflected by the subject 2100 (measurement target) (see FIG. 32A ). Light L2 is light emitted by the light emitting device 2001 that is reflected by the subject 2100. Light L1 is, for example, visible light, and light L2 is, for example, infrared light.

[0220] Light L1 can be detected by a photoelectric conversion unit in the photodetector 2002, and light L2 can be detected by a photoelectric conversion unit in the photodetector 2002. Image information of the object 2100 can be obtained from light L1, and distance information between the object 2100 and the photodetector system 2000 can be obtained from light L2.

[0221] The light detection system 2000 can be mounted on, for example, an electronic device such as a smartphone or a mobile object such as a car. The light emitting device 2001 can be configured using, for example, a semiconductor laser, a surface emitting semiconductor laser, or a vertical cavity surface emitting laser (VCSEL).

[0222] The method of detecting the light L2 emitted from the light emitting device 2001 by the photodetector 2002 can be, for example, an iTOF system, but is not limited to this. In the iTOF system, the photoelectric conversion unit can measure the distance to the subject 2100 by, for example, time-of-flight (TOF).

[0223] For example, a structured light method or a stereo vision method can be adopted as a method for detecting the light L2 emitted from the light emitting device 2001 by the light detection device 2002. For example, in the structured light method, a predetermined pattern of light is projected onto the subject 2100, and the degree of distortion of the pattern is analyzed to measure the distance between the light detection system 2000 and the subject 2100.

[0224] In addition, in the stereo vision method, for example, two or more cameras are used to acquire two or more images of the subject 2100 viewed from two or more different viewpoints, thereby making it possible to measure the distance between the light detection system 2000 and the subject. Note that the light emitting device 2001 and the light detection device 2002 can be synchronously controlled by a system control unit 2003.

[0225] 4. Application Examples (Application Examples to Mobile Bodies) The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0226] FIG. 33 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0227] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 33, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (Interface) 12053.

[0228] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0229] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0230] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0231] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0232] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0233] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0234] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0235] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0236] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying information to vehicle occupants or the outside of the vehicle. In the example of Fig. 33, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0237] FIG. 34 is a diagram showing an example of the installation position of the imaging unit 12031.

[0238] In FIG. 34, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0239] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0240] 34 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0241] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0242] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation.

[0243] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0244] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0245] An example of a mobile object control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to, for example, the image capturing unit 12031 of the above-described configuration. Specifically, for example, the image capturing device 1 or the like can be applied to the image capturing unit 12031. By applying the technology according to the present disclosure to the image capturing unit 12031, it becomes possible to obtain high-resolution captured images. It becomes possible to perform high-precision control using captured images in the mobile object control system.

[0246] (Application Example to Endoscopic Surgery System) The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be applied to an endoscopic surgery system.

[0247] FIG. 35 is a diagram showing an example of a schematic configuration of an endoscopic surgery system to which the technology according to the present disclosure (the present technology) can be applied.

[0248] 35 shows an operator (doctor) 11131 performing surgery on a patient 11132 on a patient bed 11133 using an endoscopic surgery system 11000. As shown in the figure, the endoscopic surgery system 11000 is composed of an endoscope 11100, other surgical tools 11110 such as an insufflation tube 11111 and an energy treatment tool 11112, a support arm device 11120 that supports the endoscope 11100, and a cart 11200 on which various devices for endoscopic surgery are mounted.

[0249] The endoscope 11100 is composed of a lens barrel 11101, a region of a predetermined length from the tip of which is inserted into a body cavity of a patient 11132, and a camera head 11102 connected to the base end of the lens barrel 11101. In the example shown, the endoscope 11100 is configured as a so-called rigid scope having a rigid lens barrel 11101, but the endoscope 11100 may also be configured as a so-called flexible scope having a flexible lens barrel.

[0250] An opening into which an objective lens is fitted is provided at the tip of the lens barrel 11101. A light source device 11203 is connected to the endoscope 11100, and light generated by the light source device 11203 is guided to the tip of the lens barrel by a light guide extending inside the lens barrel 11101, and is irradiated via the objective lens toward an object to be observed inside the body cavity of the patient 11132. The endoscope 11100 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0251] An optical system and an image sensor are provided inside the camera head 11102, and light reflected from the object of observation (observation light) is collected by the optical system onto the image sensor. The observation light is photoelectrically converted by the image sensor to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observed image. The image signal is sent to a camera control unit (CCU) 11201 as RAW data.

[0252] The CCU 11201 is configured with a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and comprehensively controls the operations of the endoscope 11100 and the display device 11202. Furthermore, the CCU 11201 receives an image signal from the camera head 11102 and performs various types of image processing on the image signal, such as development processing (demosaic processing), to display an image based on the image signal.

[0253] Under the control of the CCU 11201, the display device 11202 displays an image based on an image signal that has been subjected to image processing by the CCU 11201.

[0254] The light source device 11203 is composed of a light source such as an LED (Light Emitting Diode), and supplies the endoscope 11100 with irradiation light when photographing the surgical site, etc.

[0255] The input device 11204 is an input interface for the endoscopic surgery system 11000. A user can input various information and instructions to the endoscopic surgery system 11000 via the input device 11204. For example, the user inputs an instruction to change the imaging conditions (type of irradiation light, magnification, focal length, etc.) of the endoscope 11100.

[0256] The treatment tool control device 11205 controls the driving of the energy treatment tool 11112 for cauterizing tissue, incising, sealing blood vessels, etc. The insufflation device 11206 inflates the body cavity of the patient 11132 through the insufflation tube 11111 in order to ensure a clear field of view for the endoscope 11100 and a working space for the surgeon. The recorder 11207 is a device capable of recording various types of information related to the surgery. The printer 11208 is a device capable of printing various types of information related to the surgery in various formats such as text, images, or graphs.

[0257] The light source device 11203, which supplies illumination light to the endoscope 11100 when photographing the surgical site, can be configured from a white light source, such as an LED, a laser light source, or a combination of these. When the white light source is configured from a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, allowing the light source device 11203 to adjust the white balance of the captured image. In this case, it is also possible to time-share images corresponding to each RGB by irradiating the object of observation with laser light from each RGB laser light source and controlling the drive of the image sensor of the camera head 11102 in synchronization with the irradiation timing. According to this method, color images can be obtained without providing a color filter to the image sensor.

[0258] Furthermore, the light source device 11203 may be controlled to change the intensity of light it outputs at predetermined time intervals. By controlling the driving of the image sensor of the camera head 11102 in synchronization with the timing of the change in light intensity to acquire images in a time-division manner and combining the images, it is possible to generate an image with a high dynamic range that is free from so-called blocked-up shadows and blown-out highlights.

[0259] The light source device 11203 may also be configured to supply light in a predetermined wavelength band corresponding to special light observation. Special light observation, for example, utilizes the wavelength dependence of light absorption in body tissues to irradiate light in a narrower band than the light irradiated during normal observation (i.e., white light) to capture high-contrast images of specific tissues, such as blood vessels on the surface of mucous membranes, in what is known as narrow band imaging. Alternatively, special light observation may involve fluorescence observation, in which images are obtained using fluorescence generated by irradiating excitation light. Fluorescence observation may involve irradiating excitation light onto body tissues and observing the fluorescence from the tissues (autofluorescence observation), or may involve locally injecting a reagent such as indocyanine green (ICG) into the body tissue and irradiating the tissues with excitation light corresponding to the fluorescent wavelength of the reagent to obtain a fluorescent image. The light source device 11203 may be configured to supply narrow band light and / or excitation light corresponding to such special light observation.

[0260] FIG. 36 is a block diagram showing an example of the functional configuration of the camera head 11102 and the CCU 11201 shown in FIG.

[0261] The camera head 11102 has a lens unit 11401, an imaging unit 11402, a drive unit 11403, a communication unit 11404, and a camera head control unit 11405. The CCU 11201 has a communication unit 11411, an image processing unit 11412, and a control unit 11413. The camera head 11102 and the CCU 11201 are connected to each other via a transmission cable 11400 so that they can communicate with each other.

[0262] The lens unit 11401 is an optical system provided at the connection portion with the lens barrel 11101. Observation light taken in from the tip of the lens barrel 11101 is guided to the camera head 11102 and enters the lens unit 11401. The lens unit 11401 is composed of a combination of multiple lenses including a zoom lens and a focus lens.

[0263] The imaging unit 11402 is composed of an imaging element. The imaging element constituting the imaging unit 11402 may be a single (so-called single-chip type) or multiple (so-called multi-chip type). When the imaging unit 11402 is composed of a multi-chip type, for example, each imaging element may generate an image signal corresponding to each of RGB, and a color image may be obtained by combining these signals. Alternatively, the imaging unit 11402 may be configured to have a pair of imaging elements for acquiring image signals for the right eye and the left eye corresponding to 3D (dimensional) display. The 3D display allows the surgeon 11131 to more accurately grasp the depth of the biological tissue at the surgical site. Note that when the imaging unit 11402 is composed of a multi-chip type, multiple lens units 11401 may be provided corresponding to each imaging element.

[0264] Furthermore, the imaging unit 11402 does not necessarily have to be provided in the camera head 11102. For example, the imaging unit 11402 may be provided inside the lens barrel 11101, immediately after the objective lens.

[0265] The driving unit 11403 is configured by an actuator, and moves the zoom lens and focus lens of the lens unit 11401 by a predetermined distance along the optical axis under the control of the camera head control unit 11405. This allows the magnification and focus of the image captured by the imaging unit 11402 to be adjusted appropriately.

[0266] The communication unit 11404 is configured by a communication device for transmitting and receiving various types of information to and from the CCU 11201. The communication unit 11404 transmits the image signal obtained from the imaging unit 11402 to the CCU 11201 via the transmission cable 11400 as RAW data.

[0267] Furthermore, the communication unit 11404 receives a control signal for controlling the driving of the camera head 11102 from the CCU 11201 and supplies the control signal to the camera head control unit 11405. The control signal includes information on the imaging conditions, such as information specifying the frame rate of the captured image, information specifying the exposure value at the time of imaging, and / or information specifying the magnification and focus of the captured image.

[0268] The image capturing conditions such as the frame rate, exposure value, magnification, and focus may be appropriately specified by the user, or may be automatically set by the control unit 11413 of the CCU 11201 based on the acquired image signal. In the latter case, the endoscope 11100 is equipped with a so-called AE (Auto Exposure) function, AF (Auto Focus) function, and AWB (Auto White Balance) function.

[0269] The camera head control unit 11405 controls the driving of the camera head 11102 based on a control signal received from the CCU 11201 via the communication unit 11404 .

[0270] The communication unit 11411 is configured by a communication device for transmitting and receiving various information to and from the camera head 11102. The communication unit 11411 receives an image signal transmitted from the camera head 11102 via the transmission cable 11400.

[0271] Furthermore, the communication unit 11411 transmits to the camera head 11102 a control signal for controlling the driving of the camera head 11102. The image signal and the control signal can be transmitted by electrical communication, optical communication, or the like.

[0272] The image processing unit 11412 performs various image processing operations on the image signal, which is RAW data transmitted from the camera head 11102 .

[0273] The control unit 11413 performs various controls related to the imaging of the surgical site, etc. by the endoscope 11100 and the display of the captured image obtained by imaging the surgical site, etc. For example, the control unit 11413 generates a control signal for controlling the driving of the camera head 11102.

[0274] Furthermore, the control unit 11413 displays the captured image showing the surgical site, etc., on the display device 11202 based on the image signal subjected to image processing by the image processing unit 11412. At this time, the control unit 11413 may recognize various objects in the captured image using various image recognition technologies. For example, the control unit 11413 can recognize surgical tools such as forceps, specific biological parts, bleeding, mist generated when using the energy treatment tool 11112, etc., by detecting the shape and color of the edges of objects included in the captured image. When displaying the captured image on the display device 11202, the control unit 11413 may use the recognition results to superimpose various surgical support information on the image of the surgical site. By superimposing the surgical support information and presenting it to the surgeon 11131, the burden on the surgeon 11131 can be reduced and the surgeon 11131 can proceed with the surgery reliably.

[0275] The transmission cable 11400 connecting the camera head 11102 and the CCU 11201 is an electrical signal cable for electrical signal communication, an optical fiber for optical communication, or a composite cable of these.

[0276] In the illustrated example, communication is performed wired using a transmission cable 11400, but communication between the camera head 11102 and the CCU 11201 may also be performed wirelessly.

[0277] The above describes an example of an endoscopic surgery system to which the technology according to the present disclosure can be applied. Of the above-described configurations, the technology according to the present disclosure can be suitably applied to, for example, the imaging unit 11402 provided in the camera head 11102 of the endoscope 11100. By applying the technology according to the present disclosure to the imaging unit 11402, it is possible to provide a high-definition endoscope 11100.

[0278] Although the present disclosure has been described above by way of embodiments, modifications, application examples, and applied examples, the present technology is not limited to the above-described embodiments, etc., and various modifications are possible. For example, although the modifications described above have been described as modifications of the above-described embodiments, the configurations of the modifications can be combined as appropriate.

[0279] In the above embodiments, an imaging device has been described as an example. However, the photodetector of the present disclosure may be, for example, a device that receives incident light and converts the light into an electric charge. The output signal may be a signal of image information or a signal of ranging information. The photodetector (imaging device) may be applied to an image sensor, a ranging sensor, etc. Note that the present disclosure is not limited to a back-illuminated image sensor, but may also be applied to a front-illuminated image sensor.

[0280] The photodetector according to the present disclosure may also be applied as a distance measuring sensor capable of measuring distances using a time-of-flight (TOF) method. The photodetector (image capture device) may also be applied as a sensor capable of detecting events, such as an event-driven sensor (also known as an event vision sensor (EVS), an event-driven sensor (EDS), or a dynamic vision sensor (DVS)).

[0281] According to one embodiment of the present disclosure, a photodetector includes a first electrode, a second electrode disposed opposite the first electrode, a photoelectric conversion film disposed between the first electrode and the second electrode, a first semiconductor layer disposed between the photoelectric conversion film and the second electrode, and a second semiconductor layer disposed between the first semiconductor layer and the second electrode. The difference between the energy level of the conduction band minimum and the Fermi level in the first semiconductor layer is smaller than the difference between the energy level of the conduction band minimum and the Fermi level in the second semiconductor layer. This makes it possible to realize a photodetector capable of suppressing degradation of signal quality.

[0282] According to an embodiment of the present disclosure, a photodetector includes a first electrode, a second electrode disposed opposite the first electrode, a photoelectric conversion film disposed between the first electrode and the second electrode, a first semiconductor layer disposed between the photoelectric conversion film and the second electrode, and a second semiconductor layer disposed between the first semiconductor layer and the second electrode. The carrier concentration in the first semiconductor layer is higher than the carrier concentration in the second semiconductor layer. This makes it possible to realize a photodetector capable of suppressing degradation of signal quality.

[0283] Note that the effects described in this specification are merely examples and are not limited to those described, and other effects may be present. The present disclosure may also have the following configurations. (1) A photodetector including: a first electrode; a second electrode provided opposite the first electrode; a photoelectric conversion film provided between the first electrode and the second electrode; a first semiconductor layer provided between the photoelectric conversion film and the second electrode; and a second semiconductor layer provided between the first semiconductor layer and the second electrode, wherein a difference between the energy level of the conduction band minimum and the Fermi level in the first semiconductor layer is smaller than a difference between the energy level of the conduction band minimum and the Fermi level in the second semiconductor layer. (2) The photodetector according to (1) above, wherein the first semiconductor layer is a semiconductor layer containing an oxide semiconductor. (3) The photodetector according to (1) or (2) above, wherein the second semiconductor layer is a semiconductor layer containing an oxide semiconductor. (4) The photodetector according to any one of (1) to (3), wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing at least one of In, Ga, Zn, Ti, Sn, Si, Cu, Sb, and Cd. (5) The photodetector according to any one of (1) to (4), wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing In, and wherein a composition ratio of In in the first semiconductor layer is higher than a composition ratio of In in the second semiconductor layer. (6) The photodetector according to any one of (1) to (5), wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing Zn, and wherein a composition ratio of Zn in the first semiconductor layer is higher than a composition ratio of Zn in the second semiconductor layer. (7) The photodetector according to any one of (1) to (6), wherein the first semiconductor layer and the second semiconductor layer are semiconductor layers containing an oxide semiconductor, and wherein a constituent element of the first semiconductor layer is different from a constituent element of the second semiconductor layer. (8) The photodetector according to any one of (1) to (7), wherein the first semiconductor layer contains an element different from a constituent element of the second semiconductor layer.(9) The photodetector according to any one of (1) to (8), wherein a difference between the energy level of the conduction band minimum and the Fermi level in the second semiconductor layer is 0.02 eV or more greater than a difference between the energy level of the conduction band minimum and the Fermi level in the first semiconductor layer. (10) The photodetector according to any one of (1) to (9), wherein a difference between the energy level of the conduction band minimum and the vacuum level in the first semiconductor layer is greater than a difference between the energy level of the conduction band minimum and the vacuum level in the second semiconductor layer. (11) The photodetector according to any one of (1) to (10), further comprising a protective layer provided between the photoelectric conversion film and the first semiconductor layer and containing an inorganic material. (12) The photodetector according to (11), wherein the protective layer is a layer containing at least one of Ti, Si, Zr, Nb, V, Ta, Hf, Al, Sn, Sc, Y, La, Ga, and Mg. (13) The photodetector according to (11) or (12), wherein a difference between the energy level of the conduction band minimum of the protective layer and the vacuum level is smaller than a difference between the energy level of the conduction band minimum of the first semiconductor layer and the vacuum level. (14) The photodetector according to any one of (11) to (13), wherein a thickness of the protective layer is 5 nm or less. (15) The photodetector according to any one of (11) to (14), wherein the first semiconductor layer contains cations that constitute the protective layer. (16) The photodetector according to any one of (1) to (15), wherein a difference between the energy level of the conduction band minimum of the photoelectric conversion film on the first semiconductor layer side and the vacuum level is larger than a difference between the energy level of the conduction band minimum of the first semiconductor layer on the photoelectric conversion film side and the vacuum level. (17) The photodetector according to any one of (1) to (16), further comprising a first protective layer provided between the photoelectric conversion film and the first semiconductor layer and containing an inorganic material, wherein a difference between an energy level of the conduction band minimum on the first semiconductor layer side in the first protective layer and a vacuum level is larger than a difference between an energy level of the conduction band minimum on the first protective layer side in the first semiconductor layer and a vacuum level.(18) The photodetector according to (17), further comprising a second protective layer provided between the first protective layer and the first semiconductor layer and containing an inorganic material, wherein a difference between the energy level of the conduction band minimum of the second protective layer and the vacuum level is smaller than a difference between the energy level of the conduction band minimum of the first semiconductor layer and the vacuum level. (19) The photodetector according to (18), wherein a thickness of the second protective layer is 5 nm or less. (20) The photodetector according to (18) or (19), wherein the first protective layer and the second protective layer are each layers containing at least one of Ti, Si, Zr, Nb, V, Ta, Hf, Al, Sn, Sc, Y, La, Ga, and Mg. (21) The photodetector according to any one of (1) to (20), wherein a thickness of the first semiconductor layer is 10 nm or less. (22) The photodetector according to any one of (1) to (21), further comprising a third electrode provided around the second electrode in a direction orthogonal to a thickness direction of the second semiconductor layer, wherein the first semiconductor layer is provided to overlap the second electrode of the second electrode and the third electrode in a planar view. (23) The photodetector according to any one of (1) to (22), wherein the band gap of the first semiconductor layer is smaller than the band gap of the second semiconductor layer. (24) The photodetector according to (23), wherein the energy level of the conduction band minimum in the photoelectric conversion film is higher than the energy level of the conduction band minimum in the first semiconductor layer, and the energy level of the conduction band minimum in the first semiconductor layer is higher than the energy level of the conduction band minimum in the second semiconductor layer. (25) The photodetector according to (23) or (24), further comprising a protective layer containing an inorganic material provided between the photoelectric conversion film and the first semiconductor layer, wherein the energy level of the upper end of the valence band of the protective layer is higher than the energy level of the upper end of the valence band of the first semiconductor layer.(26) An electronic device comprising: an optical system; and a photodetector that receives light transmitted through the optical system, wherein the photodetector has: a first electrode; a second electrode provided so as to face the first electrode; a photoelectric conversion film provided between the first electrode and the second electrode; a first semiconductor layer provided between the photoelectric conversion film and the second electrode; and a second semiconductor layer provided between the first semiconductor layer and the second electrode, wherein a difference between an energy level of the conduction band minimum and a Fermi level in the first semiconductor layer is smaller than a difference between an energy level of the conduction band minimum and a Fermi level in the second semiconductor layer. (27) A photodetector comprising: a first electrode; a second electrode provided to face the first electrode; a photoelectric conversion film provided between the first electrode and the second electrode; a first semiconductor layer provided between the photoelectric conversion film and the second electrode; and a second semiconductor layer provided between the first semiconductor layer and the second electrode, wherein a carrier concentration in the first semiconductor layer is higher than a carrier concentration in the second semiconductor layer. (28) The photodetector according to (27), wherein the first semiconductor layer is a semiconductor layer containing an oxide semiconductor. (29) The photodetector according to (27) or (28), wherein the second semiconductor layer is a semiconductor layer containing an oxide semiconductor. (30) The carrier concentration of the first semiconductor layer is 1×10 １８ cm －３ (31) The photodetector according to any one of (27) to (29), wherein the carrier concentration of the second semiconductor layer is 1×10 or more. １８ cm －３(32) The photodetector according to any one of (27) to (31), wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing at least one of In, Ga, Zn, Ti, Sn, Si, Cu, Sb, and Cd. (33) The photodetector according to any one of (27) to (32), wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing In, and wherein a composition ratio of In in the first semiconductor layer is higher than a composition ratio of In in the second semiconductor layer. (34) The photodetector according to any one of (27) to (33), wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing Zn, and wherein a composition ratio of Zn in the first semiconductor layer is higher than a composition ratio of Zn in the second semiconductor layer. (35) The photodetector according to any one of (27) to (34), wherein the first semiconductor layer and the second semiconductor layer are each semiconductor layers containing an oxide semiconductor, and wherein a constituent element of the first semiconductor layer is different from a constituent element of the second semiconductor layer. (36) The photodetector according to any one of (27) to (35), wherein the first semiconductor layer contains an element different from a constituent element of the second semiconductor layer. (37) The photodetector according to any one of (27) to (36), further comprising a protective layer provided between the photoelectric conversion film and the first semiconductor layer and containing an inorganic material. (38) The photodetector according to (37), wherein the protective layer is a layer containing at least one of Ti, Si, Zr, Nb, V, Ta, Hf, Al, Sn, Sc, Y, La, Ga, and Mg. (39) The photodetector according to (37) or (38), wherein a difference between the energy level of the conduction band minimum of the protective layer and the vacuum level is smaller than a difference between the energy level of the conduction band minimum of the first semiconductor layer and the vacuum level. (40) The photodetector according to any one of (37) to (39), wherein a thickness of the protective layer is 5 nm or less. (41) The photodetector according to any one of (37) to (40), wherein the first semiconductor layer contains cations that constitute the protective layer.(42) The photodetector according to any one of (27) to (41), wherein a difference between the energy level of the conduction band minimum on the first semiconductor layer side in the photoelectric conversion film and the vacuum level is larger than a difference between the energy level of the conduction band minimum on the photoelectric conversion film side in the first semiconductor layer. (43) The photodetector according to any one of (27) to (42), further comprising a first protective layer provided between the photoelectric conversion film and the first semiconductor layer and containing an inorganic material, wherein a difference between the energy level of the conduction band minimum on the first semiconductor layer side in the first protective layer and the vacuum level is larger than a difference between the energy level of the conduction band minimum on the first protective layer side in the first semiconductor layer and the vacuum level. (44) The photodetector according to (43), further comprising a second protective layer provided between the first protective layer and the first semiconductor layer and containing an inorganic material, wherein a difference between the energy level of the conduction band minimum of the second protective layer and the vacuum level is smaller than a difference between the energy level of the conduction band minimum of the first semiconductor layer and the vacuum level. (45) The photodetector according to (44), wherein a thickness of the second protective layer is 5 nm or less. (46) The photodetector according to (44) or (45), wherein the first protective layer and the second protective layer are each layers containing at least one of Ti, Si, Zr, Nb, V, Ta, Hf, Al, Sn, Sc, Y, La, Ga, and Mg. (47) The photodetector according to any one of (27) to (46), wherein a thickness of the first semiconductor layer is 10 nm or less. (48) The photodetector according to any one of (27) to (47), further comprising a third electrode provided around the second electrode in a direction perpendicular to a thickness direction of the second semiconductor layer, wherein the first semiconductor layer is provided so as to overlap the second electrode of the second electrode and the third electrode in a planar view. (49) The photodetector according to any one of (27) to (48), wherein a band gap in the first semiconductor layer is smaller than a band gap in the second semiconductor layer.(50) The photodetector according to (49), wherein the energy level of the conduction band minimum in the photoelectric conversion film is higher than the energy level of the conduction band minimum in the first semiconductor layer, and the energy level of the conduction band minimum in the first semiconductor layer is higher than the energy level of the conduction band minimum in the second semiconductor layer. (51) The photodetector according to (49) or (50), further comprising a protective layer provided between the photoelectric conversion film and the first semiconductor layer and containing an inorganic material, wherein the energy level of the valence band maximum in the protective layer is higher than the energy level of the valence band maximum in the first semiconductor layer. (52) An electronic device comprising: an optical system; and a photodetector that receives light transmitted through the optical system, wherein the photodetector has: a first electrode; a second electrode provided so as to face the first electrode; a photoelectric conversion film provided between the first electrode and the second electrode; a first semiconductor layer provided between the photoelectric conversion film and the second electrode; and a second semiconductor layer provided between the first semiconductor layer and the second electrode, wherein a carrier concentration in the first semiconductor layer is higher than a carrier concentration in the second semiconductor layer.

[0284] This application claims priority based on Japanese Patent Application No. 2023-210156, filed on December 13, 2023, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0285] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. A photodetector comprising: a first electrode; a second electrode provided opposite the first electrode; a photoelectric conversion film provided between the first electrode and the second electrode; a first semiconductor layer provided between the photoelectric conversion film and the second electrode; and a second semiconductor layer provided between the first semiconductor layer and the second electrode, wherein a difference between an energy level of the conduction band minimum and a Fermi level in the first semiconductor layer is smaller than a difference between an energy level of the conduction band minimum and a Fermi level in the second semiconductor layer.

2. The photodetector according to claim 1, wherein the first semiconductor layer is a semiconductor layer containing an oxide semiconductor.

3. The photodetector according to claim 2, wherein the second semiconductor layer is a semiconductor layer containing an oxide semiconductor.

4. The photodetector device according to claim 1, wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing at least one of In, Ga, Zn, Ti, Sn, Si, Cu, Sb, and Cd.

5. The photodetector according to claim 1, wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing In, and the In composition ratio in the first semiconductor layer is greater than the In composition ratio in the second semiconductor layer.

6. The photodetector according to claim 1, wherein the first semiconductor layer and the second semiconductor layer are each an oxide semiconductor layer containing Zn, and the composition ratio of Zn in the first semiconductor layer is greater than the composition ratio of Zn in the second semiconductor layer.

7. The photodetector according to claim 1, wherein the first semiconductor layer and the second semiconductor layer are each a semiconductor layer containing an oxide semiconductor, and a constituent element of the first semiconductor layer is different from a constituent element of the second semiconductor layer.

8. The photodetector according to claim 1, wherein the first semiconductor layer contains an element different from the constituent elements of the second semiconductor layer.

9. The photodetector according to claim 1, wherein the difference between the energy level of the conduction band minimum and the Fermi level in the second semiconductor layer is greater than the difference between the energy level of the conduction band minimum and the Fermi level in the first semiconductor layer by 0.02 eV or more.

10. The photodetector according to claim 1, wherein the difference between the energy level of the conduction band minimum in the first semiconductor layer and the vacuum level is greater than the difference between the energy level of the conduction band minimum in the second semiconductor layer and the vacuum level.

11. The photodetector according to claim 1, further comprising a protective layer containing an inorganic material, the protective layer being provided between the photoelectric conversion film and the first semiconductor layer.

12. The photodetector according to claim 11, wherein the protective layer is a layer containing at least one of Ti, Si, Zr, Nb, V, Ta, Hf, Al, Sn, Sc, Y, La, Ga, and Mg.

13. The photodetector according to claim 11, wherein the difference between the energy level of the conduction band minimum of the protective layer and the vacuum level is smaller than the difference between the energy level of the conduction band minimum of the first semiconductor layer and the vacuum level.

14. The photodetector according to claim 11, wherein the protective layer has a thickness of 5 nm or less.

15. The photodetector according to claim 11, wherein the first semiconductor layer contains cations that form the protective layer.

16. The photodetector according to claim 1, wherein the difference between the energy level of the conduction band minimum on the first semiconductor layer side of the photoelectric conversion film and the vacuum level is larger than the difference between the energy level of the conduction band minimum on the photoelectric conversion film side of the first semiconductor layer and the vacuum level.

17. The photodetector according to claim 1, further comprising a first protective layer containing an inorganic material provided between the photoelectric conversion film and the first semiconductor layer, wherein a difference between the energy level of the conduction band lower end on the first semiconductor layer side of the first protective layer and the vacuum level is larger than a difference between the energy level of the conduction band lower end on the first protective layer side of the first semiconductor layer and the vacuum level.

18. The photodetector device described in claim 17, further comprising a second protective layer containing an inorganic material provided between the first protective layer and the first semiconductor layer, wherein a difference between the energy level of the conduction band minimum of the second protective layer and the vacuum level is smaller than a difference between the energy level of the conduction band minimum of the first semiconductor layer and the vacuum level.

19. The photodetector according to claim 18, wherein the second protective layer has a thickness of 5 nm or less.

20. The photodetector device according to claim 18, wherein the first protective layer and the second protective layer are each a layer containing at least one of Ti, Si, Zr, Nb, V, Ta, Hf, Al, Sn, Sc, Y, La, Ga, and Mg.

21. The photodetector according to claim 1, wherein the first semiconductor layer has a thickness of 10 nm or less.

22. The photodetector device of claim 1, further comprising a third electrode arranged around the second electrode in a direction perpendicular to the thickness direction of the second semiconductor layer, and the first semiconductor layer is arranged so as to overlap the second electrode of the second electrode and the third electrode in a planar view.

23. The photodetector device according to claim 1, wherein the band gap of the first semiconductor layer is smaller than the band gap of the second semiconductor layer.

24. The photodetector device described in claim 23, wherein the energy level of the conduction band minimum in the photoelectric conversion film is higher than the energy level of the conduction band minimum in the first semiconductor layer, and the energy level of the conduction band minimum in the first semiconductor layer is higher than the energy level of the conduction band minimum in the second semiconductor layer.

25. The photodetector device according to claim 23, further comprising a protective layer containing an inorganic material provided between the photoelectric conversion film and the first semiconductor layer, wherein the energy level of the upper end of the valence band in the protective layer is higher than the energy level of the upper end of the valence band in the first semiconductor layer.

26. An electronic device comprising: an optical system; and a photodetector that receives light transmitted through the optical system, wherein the photodetector has: a first electrode; a second electrode provided opposite the first electrode; a photoelectric conversion film provided between the first electrode and the second electrode; a first semiconductor layer provided between the photoelectric conversion film and the second electrode; and a second semiconductor layer provided between the first semiconductor layer and the second electrode, wherein a difference between an energy level of the conduction band minimum and a Fermi level in the first semiconductor layer is smaller than a difference between an energy level of the conduction band minimum and a Fermi level in the second semiconductor layer.

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