Imaging device and method using the same

Abstract

The present invention provides an imaging device and a method using the imaging device. An imaging device includes a plurality of pixels arranged one-dimensionally or two-dimensionally. Each pixel includes: a first electrode electrically connected between the plurality of pixels; a charge trapping section divided for each of the plurality of pixels; and a photoelectric conversion layer located between the first electrode and the charge trapping section and connected between the plurality of pixels. The photoelectric conversion layer includes semiconductor-type carbon nanotubes and a first substance having an electron affinity greater than that of the semiconductor-type carbon nanotubes. The charge trapping section traps positive charges. At least one of the semiconductor-type carbon nanotubes is disposed across two pixels.

Description

[0001] This application is a divisional application of the patent application for invention with the application date of June 17, 2016, application number 201680007083.4, and invention title "Imaging Device". Technical Field

[0002] This application relates to a stacked imaging device. Background Art

[0003] In recent years, a stacked image sensor having a photoelectric conversion element provided on a semiconductor substrate has been realized. In the stacked image sensor, the photoelectric conversion layer of the photoelectric conversion element can be formed of a material different from that of the semiconductor substrate. Therefore, the photoelectric conversion layer can be formed of an inorganic material or an organic material different from a conventional semiconductor material such as silicon, and an image sensor having physical properties or functions different from those of a conventional image sensor, such as sensitivity in a wavelength band different from that of the past, can be realized. For example, Patent Document 1 discloses an image sensor having a photoelectric conversion layer having sensitivity in two or more different wavelength bands, and thus having a high light utilization efficiency.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-234460 Summary of the Invention

[0007] Provided is a new stacked imaging device.

[0008] The imaging device according to a non-limiting exemplary embodiment of the present application is an imaging device including a plurality of pixels arranged one-dimensionally or two-dimensionally. Each pixel includes: a first electrode electrically connected between the plurality of pixels; a charge trapping portion divided for each of the plurality of pixels; and a photoelectric conversion layer located between the first electrode and the charge trapping portion and connected between the plurality of pixels. The photoelectric conversion layer includes semiconductor-type carbon nanotubes and a first substance having an electron affinity greater than that of the semiconductor-type carbon nanotubes. The charge trapping portion traps positive charges. At least one of the semiconductor-type carbon nanotubes is disposed across two pixels.

[0009] According to one aspect of the present application, there is provided an imaging device including carbon nanotubes as a photoelectric conversion material. Brief Description of the Drawings

[0010] Figure 1 It is a diagram showing an example of a circuit of the imaging device according to the first embodiment of the present application.

[0011] Figure 2 It shows Figure 1A schematic cross-sectional view of an example of the device structure of a unit pixel cell of the imaging device shown.

[0012] Figure 3A It shows Figure 1 A schematic cross-sectional view of an example of the structure of the photoelectric conversion section of the imaging device shown.

[0013] Figure 3B It shows Figure 1 A schematic cross-sectional view of another example of the structure of the photoelectric conversion section of the imaging device shown.

[0014] Figure 4A A schematic diagram showing an example of the structure of a carbon nanotube.

[0015] Figure 4B A schematic diagram for explaining the chirality of a carbon nanotube.

[0016] Figure 5 A graph showing the relationship between the chirality of a carbon nanotube and the first and second resonance wavelengths.

[0017] Figure 6A A schematic diagram showing the magnitude relationship of the electron affinities of the semiconductor-type carbon nanotube and the charge separation material of the imaging device according to an embodiment of the present application.

[0018] Figure 6B A schematic diagram showing the magnitude relationship of the ionization potentials of the semiconductor-type carbon nanotube and the charge separation material of the imaging device according to the first embodiment.

[0019] Figure 7 A schematic diagram for explaining the movement of charges in the photoelectric conversion section of the imaging device according to an embodiment of the present application.

[0020] Figure 8 A schematic diagram for explaining the movement of charges in a carbon nanotube.

[0021] Figure 9 A schematic cross-sectional view of an example of the structure of the photoelectric conversion section of the imaging device according to the second embodiment.

[0022] Figure 10 A schematic diagram for explaining the movement of charges in the photoelectric conversion section of the imaging device according to the second embodiment. Detailed implementation manners

[0023] Since it is used in in-vehicle cameras, surveillance cameras, etc., an imaging device with sensitivity in the near-infrared region is required. For this reason, research has been conducted on using an organic semiconductor material with sensitivity in the near-infrared region as the photoelectric conversion material of the photoelectric conversion element. As a material having absorption in the near-infrared region, the inventors of the present application have focused on carbon nanotubes.

[0024] The molecules of carbon nanotubes generally have a tube shape with a length of about several tens of nm to several mm, and have unique characteristics not seen in various conventional organic materials and inorganic materials. In particular, the mobility of electrons and holes in carbon nanotubes is known to be very large.

[0025] The inventors of the present application utilized such characteristics of carbon nanotubes and conceived a new imaging device capable of high-speed operation. The gist of one technical solution of the present application is as follows.

[0026] [Item 1]

[0027] An imaging device includes a plurality of pixels arranged one-dimensionally or two-dimensionally. Each pixel includes: an electrode electrically connected among the plurality of pixels; a charge trapping section divided for each of the pixels; and a photoelectric conversion layer located between the electrode and the charge trapping section and connected among the plurality of pixels. The photoelectric conversion layer includes one of a first substance and a second substance, and semiconducting carbon nanotubes. The first substance has a larger electron affinity than the semiconducting carbon nanotubes, and the second substance has a smaller ionization potential than the semiconducting carbon nanotubes. According to this structure, an imaging device having carbon nanotubes as a photoelectric conversion material can be obtained. In addition, by including a substance having a larger electron affinity than the semiconducting carbon nanotubes or a substance having a smaller ionization potential than the semiconducting carbon nanotubes, an imaging device capable of suppressing mixing of detected charges between pixels, obtaining a high-definition image, or having a small pixel size can be realized.

[0028] [Item 2]

[0029] In the imaging device according to Item 1, the photoelectric conversion layer includes the first substance, and the charge trapping section traps negative charges. According to this structure, negative charges can be detected as signal charges.

[0030] [Item 3]

[0031] In the imaging device according to Item 1, the photoelectric conversion layer includes the second substance, and the charge trapping section traps positive charges. According to this structure, positive charges can be detected as signal charges.

[0032] [Item 4]

[0033] In the imaging device according to any one of Items 1 to 3, a semiconductor substrate for supporting the photoelectric conversion layer is further provided; each pixel further includes a charge detection transistor provided on the semiconductor substrate and electrically connected to the charge trapping section. According to this structure, a stacked imaging device can be realized.

[0034] [Item 5]

[0035] The imaging device according to any one of Items 1 to 4, in the above photoelectric conversion layer, one of the above first substance and the above second substance and the above semiconductor carbon nanotubes are mutually dispersed. According to this structure, mixing of charges between pixels can be more reliably suppressed.

[0036] [Item 6]

[0037] The imaging device according to Item 4, the above charge trapping portion is an impurity diffusion region formed in the above semiconductor substrate.

[0038] [Item 7]

[0039] The imaging device according to Item 4, the above charge trapping portion is an electrode located on the above semiconductor substrate.

[0040] [Item 8]

[0041] The imaging device according to Item 2, the above first substance is a molecule having a fullerene skeleton. According to this structure, negative charges can be detected as signal charges.

[0042] [Item 9]

[0043] The imaging device according to Item 3, further includes a voltage supply circuit, which is electrically connected to the above electrode and generates a bias voltage determined to make the potential of the above charge trapping portion higher than the potential of the above electrode.

[0044] [Item 10]

[0045] The imaging device according to Item 2, further includes a voltage supply circuit, which is electrically connected to the above electrode and generates a bias voltage determined to make the potential of the above charge trapping portion lower than the potential of the above electrode.

[0046] [Item 11]

[0047] An imaging device includes a plurality of pixels arranged one-dimensionally or two-dimensionally. Each pixel includes: an electrode electrically connected between the above plurality of pixels; a charge trapping portion divided for each of the above pixels; and a photoelectric conversion layer containing one of a first substance and a second substance, and a semiconducting carbon nanotube, sandwiched between the above electrode and the above charge trapping portion. The above first substance has a larger electron affinity than the above semiconducting carbon nanotube, and the above second substance has a smaller ionization potential than the above semiconducting carbon nanotube; at least a part of the above semiconducting carbon nanotube is electrically connected to the above charge trapping portion. According to this structure, a semiconducting carbon nanotube with a relatively high carrier mobility is included, and charges moving in the semiconducting carbon nanotube are trapped by the pixel electrode. Therefore, an imaging device capable of high-speed operation and capable of shooting at a high frame rate can be realized.

[0048] [Item 12]

[0049] The imaging device according to Item 11, wherein the above photoelectric conversion layer contains the above first substance, and the above charge trapping portion traps positive charges. According to this structure, positive charges can be detected as signal charges.

[0050] [Item 13]

[0051] The imaging device according to Item 11, wherein the above photoelectric conversion layer contains the above second substance, and the above charge trapping portion traps negative charges. According to this structure, negative charges can be detected as signal charges.

[0052] [Item 14]

[0053] The imaging device according to any one of Items 11 to 13 further includes a semiconductor substrate that supports the above photoelectric conversion layer; each of the above pixels further includes a charge detection transistor that is disposed on the above semiconductor substrate and is electrically connected to the above charge trapping portion. According to this structure, a stacked imaging device can be realized.

[0054] [Item 15]

[0055] The imaging device according to Item 14, wherein the above charge trapping portion is an impurity diffusion region formed in the above semiconductor substrate.

[0056] [Item 16]

[0057] The imaging device according to Item 14, wherein the above charge trapping portion is an electrode located on the above semiconductor substrate.

[0058] [Item 17]

[0059] The imaging device according to Item 12, wherein the above first substance is a molecule having a fullerene skeleton. According to this structure, positive charges can be detected as signal charges.

[0060] [Item 18]

[0061] The imaging device according to Item 12 further includes a voltage supply circuit that is electrically connected to the above electrode and generates a bias voltage determined to make the potential of the above charge trapping portion lower than the potential of the above electrode.

[0062] [Item 19]

[0063] The imaging device according to Item 13 further includes a voltage supply circuit that is electrically connected to the above electrode and generates a bias voltage determined to make the potential of the above charge trapping portion higher than the potential of the above electrode.

[0064] Hereinafter, embodiments of the present application will be described in detail. In addition, the embodiments described below are all general or specific examples. The numerical values, shapes, materials, constituent elements, arrangements and connection forms of the constituent elements, steps, order of steps, etc. shown in the following embodiments are examples and do not limit the meaning of the present application. Various forms described in this specification can be combined with each other as long as there is no contradiction. In addition, regarding the constituent elements in the following embodiments that are not described in the independent claims representing the most general concept, they are described as arbitrary constituent elements. In the following description, there are cases where constituent elements having substantially the same function are denoted by the same reference numerals and the description is omitted.

[0065] (First Embodiment)

[0066] [1. Overall Structure of the Imaging Device]

[0067] Refer to Figure 1 to outline the structure of the imaging device of the present application. Figure 1 An example of the circuit structure of the imaging device according to the embodiment of the present application is shown. Figure 1 The imaging device 100 shown has a plurality of unit pixel units 20 and a peripheral circuit. The peripheral circuit includes a voltage supply circuit 10 that supplies a predetermined voltage to each unit pixel unit 20.

[0068] The unit pixel units 20 are arranged one-dimensionally or two-dimensionally on a semiconductor substrate to form a photosensitive region (pixel region). In Figure 1 the illustrated structure, the unit pixel units 20 are arranged in the row direction and the column direction. In this specification, the row direction and the column direction respectively refer to the directions in which the rows and columns extend. That is, Figure 1 the vertical direction in the plane of Figure 1 is the column direction, and the horizontal direction is the row direction. In Figure 1 four unit pixel units 20 arranged in a 2×2 matrix are shown.

[0069] Each unit pixel unit 20 has a photoelectric conversion unit 30 and a signal detection circuit 40 that detects a signal generated by the photoelectric conversion unit 30. The photoelectric conversion unit 30 includes a pixel electrode (charge trapping unit) 32 and a counter electrode 38, and a photoelectric conversion layer 39 disposed therebetween. As shown in the figure, the counter electrode (electrode) 38 is connected to the voltage supply circuit 10 via an accumulation control line 22. During the operation of the imaging device 100, a predetermined bias voltage is applied to the counter electrode 38 via the accumulation control line 22.

[0070] As described in detail below, the photoelectric conversion layer 39 is configured to include semiconductor-type carbon nanotubes. Among the hole-electron pairs generated by photoelectric conversion, the pixel electrode 32 captures either holes (positive charges) or electrons (negative charges) as signal charges. By controlling the potential of the counter electrode 38 using the bias voltage generated by the voltage supply circuit 10, it is possible to capture either holes or electrons with the pixel electrode 32. For example, when using holes as signal charges, a voltage of about 10 V is applied to the storage control line 22 to make the potential of the counter electrode 38 higher than that of the pixel electrode 32.

[0071] In Figure 1 In the illustrated structure, the signal detection circuit 40 includes an amplification transistor (charge detection transistor) 42, an address transistor (row selection transistor) 44, and a reset transistor 46. Typically, the amplification transistor 42 and the address transistor 44 are field effect transistors (FETs) formed on a semiconductor substrate. Hereinafter, unless otherwise specified, an example of using an N-channel MOS as a transistor will be described. In addition, the "semiconductor substrate" in this specification is not limited to a substrate that is entirely semiconductor, and may also be an insulating substrate provided with a semiconductor layer on the surface on the photosensitive region side. An example of the semiconductor substrate is a p-type silicon substrate.

[0072] As shown in the figure, one of the input terminal and the output terminal of the amplification transistor 42 (typically the source) is connected to one of the input terminal and the output terminal of the address transistor 44 (typically the drain). The control terminal (gate) of the amplification transistor 42 is electrically connected to the pixel electrode 32 of the photoelectric conversion unit 30. The signal charges (e.g., holes) collected by the pixel electrode 32 are accumulated in the charge accumulation node (also referred to as "floating diffusion node") 41 between the pixel electrode 32 and the gate of the amplification transistor 42.

[0073] A voltage corresponding to the signal charges accumulated in the charge accumulation node 41 is applied to the gate of the amplification transistor 42. The amplification transistor 42 amplifies this voltage. That is, the amplification transistor 42 amplifies the signal generated by the photoelectric conversion unit 30. The voltage amplified by the amplification transistor 42 is selectively read out as a signal voltage via the address transistor 44.

[0074] One of the source and the drain of the reset transistor 46 is connected to the charge accumulation node 41, and one of the source and the drain of the reset transistor 46 has an electrical connection to the pixel electrode 32.

[0075] The reset transistor 46 resets the signal charges accumulated in the charge accumulation node 41. In other words, the reset transistor 46 resets the potential of the gate of the amplification transistor 42 and the pixel electrode 32.

[0076] As shown in the figure, the imaging device 100 includes a power supply line 23, a vertical signal line 24, an address signal line 25, and a reset signal line 26. These lines are connected to each unit pixel unit 20. The power supply line (source follower power supply) 23 is connected to one of the source and drain of the amplification transistor 42, and supplies a predetermined power supply voltage to each unit pixel unit 20. The vertical signal line 24 is connected to the side of the source and drain of the address transistor 44 that is not connected to the source or drain of the amplification transistor 42. The address signal line 25 is connected to the gate electrode of the address transistor 44. The reset signal line 26 is connected to the gate of the reset transistor 46.

[0077] The peripheral circuit of the imaging device 100 includes a vertical scanning circuit (also referred to as a "row scanning circuit") 52, a horizontal signal reading circuit (also referred to as a "column scanning circuit") 54, a plurality of column signal processing circuits (also referred to as "row signal accumulation circuits") 56, a plurality of load circuits 58, and a plurality of inverter amplifiers 59. The column signal processing circuits 56, the load circuits 58, and the inverter amplifiers 59 are provided corresponding to each column of the plurality of unit pixel units 20 arranged in the row direction and the column direction. The column signal processing circuits 56 are electrically connected to the unit pixel units 20 arranged in each column via the vertical signal lines 24 corresponding to each column of the plurality of unit pixel units 20. The plurality of column signal processing circuits 56 are electrically connected to the horizontal signal reading circuit 54. The load circuits 58 are electrically connected to the respective vertical signal lines 24, and a source follower circuit is formed by the load circuits 58 and the amplification transistors 42.

[0078] The vertical scanning circuit 52 is connected to the address signal line 25 and the reset signal line 26. The vertical scanning circuit 52 applies a row selection signal for controlling the conduction and cutoff of the address transistor 44 to the gate of the address transistor 44 via the address signal line 25. By sending the row selection signal for each address signal line 25, the row to be read is scanned and selected. A signal voltage is read from the unit pixel units 20 of the selected row to the vertical signal line 24. In addition, the vertical scanning circuit 52 applies a reset signal for controlling the conduction and cutoff of the reset transistor 46 to the gate of the reset transistor 46 via the reset signal line 26. By sending the row selection signal for each reset signal line 26, the row of the unit pixel units 20 that is the object of the reset operation is selected. In this way, the vertical scanning circuit 52 selects a plurality of unit pixel units 20 in row units, reads the signal voltage, and resets the potential of the pixel electrode 32.

[0079] The signal voltage read out from the unit pixel unit 20 selected by the vertical scanning circuit 52 is sent to the column signal processing circuit 56 via the vertical signal line 24. The column signal processing circuit 56 performs noise suppression signal processing typified by correlated double sampling and analog-to-digital conversion (AD conversion), etc. The horizontal signal readout circuit 54 sequentially reads out signals from the plurality of column signal processing circuits 56 to a horizontal common signal line (not shown).

[0080] In addition, the vertical scanning circuit 52 may partially include the voltage supply circuit 10. Alternatively, the voltage supply circuit 10 may have an electrical connection with the vertical scanning circuit 52. In other words, the bias voltage may be applied to the counter electrode 38 via the vertical scanning circuit 52.

[0081] In Figure 1 In the illustrated structure, a plurality of inverter amplifiers 59 are provided corresponding to each column. The negative input terminal of the inverter amplifier 59 is connected to the corresponding vertical signal line 24. The output terminal of the inverter amplifier 59 is connected to each unit pixel unit 20 of the corresponding column via a feedback line 27 provided corresponding to each column.

[0082] As shown in the figure, the feedback line 27 is connected to the side (drain) of the source and drain of the reset transistor 46 that is not connected to the charge storage node 41. Therefore, when the address transistor 44 and the reset transistor 46 are in the conductive state, the inverter amplifier 59 receives the output of the address transistor 44 at the negative terminal. On the other hand, a reset reference voltage is applied to the positive input terminal of the inverter amplifier 59 from a power supply (not shown). The inverter amplifier 59 performs a feedback operation to make the gate voltage of the amplification transistor 42 a prescribed feedback voltage. The feedback voltage refers to the output voltage of the inverter amplifier 59. The output voltage of the inverter amplifier 59 is, for example, 0V or a positive voltage near 0V. The inverter amplifier 59 may also be referred to as a "feedback amplifier".

[0083] [2. Device Structure of the Imaging Device]

[0084] Figure 2 Schematically shows a cross-section of the device structure of the unit pixel unit 20 in the imaging device 100 according to an embodiment of the present application. In Figure 2In the illustrated structure, the unit pixel unit 20 includes a semiconductor substrate 62 (e.g., a silicon substrate) that supports the photoelectric conversion unit 30. As shown in the figure, the photoelectric conversion unit 30 is disposed above the semiconductor substrate 62. In this example, an interlayer insulating layer 63A, 63B, and 63C are stacked on the semiconductor substrate 62, and a stacked body of a pixel electrode 32, a photoelectric conversion layer 39, and a counter electrode 38 is disposed on the interlayer insulating layer 63C. The pixel electrode 32 is divided for each pixel, and between two adjacent unit pixel units 20, the pixel electrode 32 is spatially separated and formed, and two adjacent pixel electrodes 32 are electrically separated. In addition, the photoelectric conversion layer 39 and the counter electrode 38 are formed so as to straddle a plurality of unit pixel units 20. The counter electrode 38 is formed of, for example, a metal oxide such as ITO or ZnO, several layers of graphene, metal nanowires, or the like.

[0085] In the semiconductor substrate 62, an amplifying transistor 42, an address transistor 44, and a reset transistor 46 are formed.

[0086] The amplifying transistor 42 includes impurity regions 62a and 62b formed in the semiconductor substrate 62, a gate insulating layer 42g located on the semiconductor substrate 62, and a gate electrode 42e located on the gate insulating layer 42g. The impurity regions (n-type impurity regions) 62a and 62b function as the drain or source of the amplifying transistor 42.

[0087] The address transistor 44 includes impurity regions 62a and 62c formed in the semiconductor substrate 62, a gate insulating layer 44g located on the semiconductor substrate 62, and a gate electrode 44e located on the gate insulating layer 44g. The impurity regions (n-type impurity regions) 62a and 62c function as the drain or source of the address transistor 44. In this example, the amplifying transistor 42 and the address transistor 44 share the impurity region 62a, and the source (or drain) of the amplifying transistor 42 is electrically connected to the drain (or source) of the address transistor 44.

[0088] The reset transistor 46 includes impurity regions 62d and 62e formed in the semiconductor substrate 62, a gate insulating layer 46g located on the semiconductor substrate 62, and a gate electrode 46e located on the gate insulating layer 46g. The impurity regions (n-type impurity regions) 62d and 62e function as the drain or source of the reset transistor 46.

[0089] In the semiconductor substrate 62, element isolation regions 62s are provided between adjacent unit pixel cells 20 and between the amplification transistor 42 and the reset transistor 46. Through the element isolation regions 62s, the adjacent unit pixel cells 20 are electrically separated. In addition, by providing the element isolation regions 62s between adjacent unit pixel cells 20, leakage of the signal charge stored in the charge storage node 41 is suppressed.

[0090] In the interlayer insulating layer 63A, a contact plug 65A connected to the impurity region 62d of the reset transistor 46, a contact plug 65B connected to the gate electrode 42e of the amplification transistor 42, and a wiring 66A connecting the contact plug 65A and the contact plug 65B are formed. Thus, the n-type impurity region 62d (e.g., the drain) of the reset transistor 46 and the gate electrode 42e of the amplification transistor 42 are electrically connected. In Figure 2 In the illustrated structure, a plug 67A and a wiring 68A are also formed in the interlayer insulating layer 63A. In addition, a plug 67B and a wiring 68B are formed in the interlayer insulating layer 63B, and a plug 67C is formed in the interlayer insulating layer 63C, whereby the wiring 66A and the pixel electrode 32 are electrically connected. The contact plug 65A, the contact plug 65B, the wiring 66A, the plug 67A, the wiring 68A, the plug 67B, the wiring 68B, and the plug 67C are typically made of metal.

[0091] In Figure 2 In the illustrated structure, a protective layer 72 is provided on the counter electrode 38. The protective layer 72 is not a substrate configured to support the photoelectric conversion unit 30. As Figure 2 shown, a microlens may also be disposed on the protective layer 72.

[0092] [3. Structure of the Photoelectric Conversion Layer]

[0093] Next, the photoelectric conversion layer 39 of the photoelectric conversion unit 30 will be described in detail. Figure 3A The cross-section of the photoelectric conversion unit 30 of the unit pixel cell 20 is schematically shown. In each unit pixel cell 20, the photoelectric conversion unit 30 includes a counter electrode 38, a pixel electrode 32, and a photoelectric conversion layer 39. The photoelectric conversion layer 39 is sandwiched between the counter electrode 38 and the pixel electrode 32.

[0094] From the viewpoint of suppressing the occurrence of leakage current, the photoelectric conversion layer 39 is not separated for each pixel. That is, the photoelectric conversion layer 39 is formed across a plurality of unit pixel cells 20. The photoelectric conversion layer 39 includes semiconductor-type carbon nanotubes 105 and a charge separation material 106.

[0095] The carbon nanotubes will be described in detail. As Figure 4AAs shown, a carbon nanotube has a structure in which a single-layer graphite sheet formed by arranging carbon atoms called graphene at the vertices of a hexagon is circularized into a cylindrical shape. In carbon nanotubes, there are single-walled carbon nanotubes and multi-walled carbon nanotubes. In the imaging device of the present application, either single-walled carbon nanotubes or multi-walled carbon nanotubes can be used. However, from the viewpoint of controlling the physical properties of carbon nanotubes according to the chirality described below, it is preferable to use single-walled carbon nanotubes.

[0096] In the case of circularizing graphene into a cylindrical shape, carbon nanotubes with different diameters and carbon arrangements can be formed according to the thickness of the cylinder formed and the degree to which the graphene sheets are offset in the length direction to close the two end edges of the sheets. As Figure 4B shown, in the arrangement of carbon atoms two-dimensionally located at the vertices of a hexagon, a rectangle with basic lattice vectors a1 and a2 and OP and OQ as two sides can be considered. If point O is taken as the origin, point P is represented by the vector (6, 3). When this rectangle is circularized so that point P overlaps with point O, the resulting carbon nanotube is called a carbon nanotube with chirality (6, 3).

[0097] By specifying the chirality, the positions of carbon atoms in the carbon nanotube are determined. Therefore, the electronic structure of the carbon nanotube is determined according to the chirality, and the physical properties of the carbon nanotube are determined. That is, any carbon nanotube is specified by a chirality vector represented by C = na1 + ma2 (n, m are integers). At this time, (n, |m|) is called the index or chirality of the chirality. Here, |m| represents the absolute value of m. In this expression of chirality, the right-handed and left-handed carbon nanotubes are not distinguished.

[0098] Among carbon nanotubes, there are carbon nanotubes with metallicity and carbon nanotubes with semiconductivity. Whether a carbon nanotube has metallicity or semiconductivity depends on the chirality. In the imaging device of the present application, semiconductor-type carbon nanotubes are used. That is, instead of using carbon nanotubes as simple electrical conductors, they are used for light detection, specifically for the generation of hole-electron pairs using photoelectric conversion. The proportion of metallic carbon nanotubes in the photoelectric conversion layer 39 is preferably small. More preferably, metallic carbon nanotubes are not included. This is because in metallic carbon nanotubes, the generated hole-electron pairs disappear rapidly.

[0099] The carrier mobility in semiconductor-type carbon nanotubes does not depend much on the chirality. Generally, both the hole mobility and the electron mobility of semiconductor-type carbon nanotubes are tens of thousands of cm 2 / Vs, which is more than 10 times faster than the electron mobility of silicon.

[0100] The resonance wavelength of a carbon nanotube, that is, the absorption wavelength, depends on the chirality. Therefore, by changing the chirality, the absorption wavelength of the carbon nanotube can be adjusted.

[0101] Figure 5 It shows the relationship between the chirality of semiconducting carbon nanotubes and the first and second resonance wavelengths. The first resonance wavelength refers to the longest wavelength at which resonance occurs, and the second resonance wavelength refers to the second longest wavelength at which resonance occurs. Although not shown in the figure, there can also be resonance wavelengths of other wavelengths in semiconducting carbon nanotubes.

[0102] According to Figure 5 it can be seen that the wavelengths that can be resonantly absorbed are distributed over the range from the visible region to the far-infrared region. In particular, in semiconducting carbon nanotubes with a diameter of around 1 nm, which are relatively easy to mass-produce, the resonance wavelengths are distributed in the near-infrared region from the visible region to around 1.6 μm in wavelength.

[0103] For example, a semiconducting carbon nanotube with chirality (8, 0) has a resonance wavelength of around 780 nm. In addition, a semiconducting carbon nanotube with chirality (7, 2) has a resonance wavelength of around 820 nm. At a wavelength of 780 nm, reduced hemoglobin exhibits higher absorption than oxidized hemoglobin, and at a wavelength of 820 nm, oxidized hemoglobin exhibits higher absorption than reduced hemoglobin. Therefore, by using semiconducting carbon nanotubes with these chiralities in the photoelectric conversion layer, an imaging device capable of imaging the blood oxygen concentration can be realized.

[0104] In addition, for example, semiconducting carbon nanotubes with chiralities (12, 4), (10, 6), (13, 0), etc. resonantly absorb near-infrared light of around 1.4 μm. This corresponds to the solar-blind band. Therefore, by using semiconducting carbon nanotubes with these chiralities in the photoelectric conversion layer and using illumination light with a wavelength of around 1.4 μm, an imaging device capable of taking pictures without being affected by sunlight can be realized.

[0105] In addition, a semiconducting carbon nanotube with chirality (8, 7) has a resonance wavelength of around 1.3 μm. This is a wavelength that is close to the solar-blind band but shows little attenuation of sunlight. Therefore, by using semiconducting carbon nanotubes with these chiralities in the photoelectric conversion layer, an imaging device capable of taking pictures based on sunlight in the vicinity of the solar-blind band can be realized.

[0106] Furthermore, each semiconducting carbon nanotube has several resonance wavelengths, and resonance wavelengths sometimes exist in the near-infrared region and the visible region. For example, the resonance of chirality (10, 6) exists not only in the infrared region of about 1.4 μm but also in the visible region of about 750 nm. Therefore, by using semiconducting carbon nanotubes with these chiralities in the photoelectric conversion layer and combining them with an optical filter, etc., an imaging device capable of multi-spectral imaging can be realized.

[0107] The photoelectric conversion layer 39 may include semiconductor carbon nanotubes 105 having a prescribed one chirality, or may include semiconductor carbon nanotubes 105 having two or more different chiralities. By including semiconductor carbon nanotubes 105 having two or more different chiralities, the wavelength band of light that the imaging device can detect can be broadened.

[0108] The diameter of the semiconductor carbon nanotubes having resonance wavelengths in the visible region and the near-infrared region is about 1 nm.

[0109] Next, the charge separation material 106 will be described in detail. The charge separation material 106 is a material having semiconductivity or a material having semimetallicity, etc. The charge separation material 106 extracts either one of the hole-electron pairs generated when the semiconductor carbon nanotubes 105 receive light from the semiconductor carbon nanotubes 105. In the present embodiment, the charge separation material 106 extracts the one that is not detected as a signal charge from the semiconductor carbon nanotubes 105.

[0110] For example, when holes are used as signal charges, the voltage supply circuit 10 supplies a bias voltage determined to make the potential of the pixel electrode 32 lower than the potential of the counter electrode 38 to the counter electrode 38. Further, in this case, as the charge separation material 106, a material having a larger electron affinity than the semiconductor carbon nanotubes 105 can be used.

[0111] As Figure 6A shown, the electron affinity in a semiconductor is defined as the energy difference from the bottom of the conduction band 110 to the vacuum level 113. When the semiconductor is an organic semiconductor, the electron affinity is the energy difference between the LUMO level and the vacuum level. More generally, it is the maximum value of the energy difference between the energy level that can accept an excess of one electron in the neutral state and the vacuum level. When the charge separation material 106 is a material having a larger electron affinity than the semiconductor carbon nanotubes 105, the electrons in the hole-electron pairs generated by the semiconductor carbon nanotubes 105 move to the conduction band 110 of the charge separation material 106 at a lower energy level. Therefore, holes remain in the valence band 111 of the semiconductor carbon nanotubes 105.

[0112] Since a bias voltage determined to make the potential of the pixel electrode 32 lower than the potential of the counter electrode 38 is supplied, holes move from the semiconductor carbon nanotubes 105 to the pixel electrode 32.

[0113] The electron affinity of a semiconducting carbon nanotube having a resonance wavelength in the visible and near-infrared regions is approximately 3 eV to 4 eV. As substances having an electron affinity greater than that of the semiconducting carbon nanotube by 105, fullerenes and fullerene derivatives are generally cited. Fullerenes and fullerene derivatives are called molecules having a fullerene skeleton. For example, C60 has an electron affinity of about 4 eV. In addition to this, C70, C80, phenyl C61 butyric acid methyl ester (PCBM) in which a modifying group is introduced into these fullerene skeletons, indene C60 bisadduct (ICBA), indene C60 monoadduct (ICMA), etc. also have an electron affinity of about 3.7 eV to 3.8 eV.

[0114] In addition, for example, when electrons are used as signal charges, the voltage supply circuit 10 supplies a bias voltage determined to make the potential of the pixel electrode 32 higher than the potential of the counter electrode 38 to the counter electrode 38. In addition, in this case, as the charge separation material 106, a substance having an ionization potential smaller than that of the semiconducting carbon nanotube 105 can be used.

[0115] As Figure 6B shown, the ionization potential in a semiconductor is defined as the energy difference from the bottom of the valence band 111 to the vacuum level 113. When the semiconductor is an organic semiconductor, the ionization potential is the energy difference between the HOMO level and the vacuum level. More generally speaking, it is the minimum value of the energy necessary to raise 1 electron from the neutral state to the vacuum level. When the charge separation material 106 is a substance having an ionization potential smaller than that of the semiconducting carbon nanotube 105, the charge separation material 106 is more stable when it is a positive ion, so the hole in the hole-electron pair generated by the semiconducting carbon nanotube 105 moves to the valence band 111 of the charge separation material 106. Therefore, electrons remain in the conduction band 110 of the semiconducting carbon nanotube 105.

[0116] Since a bias voltage determined to make the potential of the pixel electrode 32 higher than the potential of the counter electrode 38 is supplied to the counter electrode 38, electrons move from the semiconducting carbon nanotube 105 to the pixel electrode 32.

[0117] The ionization potential of a semiconducting carbon nanotube having a resonance wavelength in the visible and near-infrared regions is approximately 4 eV to 5 eV. As substances having an ionization potential smaller than that of the semiconducting carbon nanotube 105, for example, poly(3-dodecylthiophene-2,5-diyl) (P3DDT, ionization potential: about 4.6 eV), poly(3-hexylthiophene-2,5-diyl) (P3HT, ionization potential: about 5 eV), etc. can be cited.

[0118] As described above, since the electronic structure of the semiconducting carbon nanotube 105 varies according to chirality, the electron affinity and ionization potential of the semiconducting carbon nanotube 105 also vary according to chirality. Therefore, it is preferable to calculate the electron affinity and ionization potential of the semiconducting carbon nanotube 105 taking chirality into account, and select the charge separation material 106 to satisfy the above relationship.

[0119] In the photoelectric conversion layer 39, the semiconducting carbon nanotube 105 and the charge separation material 106 may be dispersed in each other. In this case, the distribution of the semiconducting carbon nanotube 105 and the charge separation material 106 may not be uniform. For example, there may be a bias in the distribution in the thickness direction of the photoelectric conversion layer 39.

[0120] Preferably, the signal charge can move from the semiconducting carbon nanotube 105 to the pixel electrode 32. In other words, it is preferable that the semiconducting carbon nanotube 105 is electrically connected to the pixel electrode 32. For example, a part of the semiconducting carbon nanotube 105 may be in direct contact with the pixel electrode 32.

[0121] As Figure 3B shown, the photoelectric conversion unit 30 may further include a hole blocking layer 103 and an electron blocking layer 101. These layers are disposed at positions where the movement of holes and electrons is to be suppressed. For example, when the pixel electrode 32 traps electrons, the hole blocking layer 103 is provided between the pixel electrode 32 and the photoelectric conversion layer 39, and the electron blocking layer 101 is provided between the counter electrode 38 and the photoelectric conversion layer 39.

[0122] The hole blocking layer 103 transports the negative charge generated by the photoelectric conversion layer 39 to the pixel electrode 32, and suppresses the intrusion of the positive charge from the pixel electrode 32 into the photoelectric conversion layer 39. In order to suppress the current flowing even in the state where no light is irradiated, that is, the so-called dark current, it is preferable to provide the hole blocking layer 103. For example, bathocuproine (BCP) can be used in the hole blocking layer 103.

[0123] The electron blocking layer 101 functions to transport the positive charge generated by the photoelectric conversion layer 39 to the counter electrode 38, and suppresses the intrusion of the negative charge from the counter electrode 38 into the photoelectric conversion layer 39. In order to suppress the dark current, it is preferable to provide the electron blocking layer 101. For example, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) can be used in the electron blocking layer 101.

[0124] The hole blocking layer 103 and the electron blocking layer 101 have electrical conductivity for transporting electrons (negative charges) and holes (positive charges), respectively. Therefore, when the hole blocking layer 103 is disposed between the pixel electrode 32 and the photoelectric conversion layer 39, a part of the semiconducting carbon nanotube 105 contacts the hole blocking layer 103, and thus a part of the semiconducting carbon nanotube 105 is electrically connected to the pixel electrode 32 via the hole blocking layer 103. In addition, when the electron blocking layer 101 is disposed between the pixel electrode 32 and the photoelectric conversion layer 39, a part of the semiconducting carbon nanotube 105 also contacts the electron blocking layer 101, and thus a part of the semiconducting carbon nanotube 105 is electrically connected to the pixel electrode 32 via the electron blocking layer 101.

[0125] When the hole blocking layer 103 is used between the photoelectric conversion layer 39 and the pixel electrode 32, it is sufficient that signal charges can move between the semiconducting carbon nanotube 105 and the hole blocking layer 103, and between the hole blocking layer 103 and the pixel electrode 32. It is also possible that a part of the semiconducting carbon nanotube 105 directly contacts the hole blocking layer 103.

[0126] As long as the signal charges can move, the semiconducting carbon nanotube 105 and the pixel electrode 32 or the hole blocking layer 103 may not directly contact each other. This is because the signal charges can move via other charge transport materials or by tunneling phenomena, etc. However, these charge transports by other charge transport materials and tunneling phenomena are generally slower than the charge transport within the semiconducting carbon nanotube 105. Therefore, it is preferable that a part of the semiconducting carbon nanotube 105 directly contacts the pixel electrode 32 or the hole blocking layer 103 as much as possible, or is distributed near the pixel electrode 32 or the hole blocking layer 103.

[0127] In addition, when holes are trapped as signal charges, the electron blocking layer 101 is used between the photoelectric conversion layer 39 and the pixel electrode 32. In this case, by replacing the entire hole blocking layer 103 with the electron blocking layer 101, the configuration of the semiconducting carbon nanotube 105 can be similarly described.

[0128] In the photoelectric conversion layer 39, it is preferable that as many molecules of the semiconducting carbon nanotube 105 as possible contact the pixel electrode 32, or are distributed closer to the pixel electrode 32. For this purpose, the density of the semiconducting carbon nanotube 105 in the thickness direction of the photoelectric conversion layer 39 may be lower on the counter electrode 38 side and higher on the pixel electrode 32 side. In this case, the density of the charge separation material 106 in the thickness direction of the photoelectric conversion layer 39 is preferably higher on the counter electrode 38 side and lower on the pixel electrode 32 side.

[0129] In addition, as Figure 3AAs shown, the photoelectric conversion layer 39 may also include a layer 39a containing only the charge separation material 106 and a layer 39b containing only the semiconductor-type carbon nanotubes 105. In this case, the layer 39b containing only the semiconductor-type carbon nanotubes 105 is in contact with the pixel electrode 32, and the layer 39a containing only the charge separation material 106 is in contact with the counter electrode 38.

[0130] The thickness of the photoelectric conversion layer 39 is, for example, several tens of nm or more and several hundreds of nm or less. In addition, the photoelectric conversion layer 39 may also include an n-type semiconductor or a p-type semiconductor.

[0131] [4. Movement of charges in the photoelectric conversion layer 39]

[0132] Refer to Figure 7 to describe the detection of incident light in the photoelectric conversion layer 39. Figure 7 is a schematic diagram showing the positional relationship between the semiconductor-type carbon nanotubes 105 and the charge separation material 106 in the photoelectric conversion layer 39 and the pixel electrode 32 and the counter electrode 38. In Figure 7 , only the semiconductor-type carbon nanotubes 105 and the charge separation material 106 of interest are shown by solid lines. In the following example, electrons are used as signal charges. In addition, the charge separation material 106 is a substance having an ionization potential smaller than that of the semiconductor-type carbon nanotubes 105. In addition, in Figure 7 , a bias voltage is supplied to the counter electrode 38 so that the potential of the pixel electrode 32 is higher than the potential of the counter electrode 38. Therefore, an electric field is generated in the direction indicated by the arrow 502.

[0133] If photons (not shown) are absorbed by the semiconductor-type carbon nanotubes 105, a positive charge (hole) h and a negative charge (electron) e are generated approximately at the position 501 thereof. The generated positive charge h and negative charge e interact with each other by gravitational force to form a state called an exciton. Since the exciton is macroscopically electrically neutral, the position of the exciton is not affected by the applied electric field, but only diffuses and moves smoothly.

[0134] If the exciton reaches a position close to the charge separation material 106, separation of the charges of the exciton occurs. Specifically, since the charge separation material 106 has an ionization potential smaller than that of the semiconductor-type carbon nanotubes 105, it is more energetically stable for the charge separation material 106 to accept the positive charge h compared to the semiconductor-type carbon nanotubes 105 continuously holding the positive charge h. Therefore, extraction of the positive charge h based on the charge separation material 106 is performed. As a result, the positive charge moves into one molecule of the charge separation material 106, and the negative charge e remains in the semiconductor-type carbon nanotubes 105.

[0135] Charge separation occurs at the position where the semiconductor-type carbon nanotube 105 is close to the charge separation material 106. Therefore, if there is more than one molecule of the charge separation material 106 in the unit pixel cell 20 around one molecule of the semiconductor-type carbon nanotube 105, charge separation occurs in the pixel where excitons are generated. In order to make the generation and charge separation of excitons occur in the same unit pixel cell, it is sufficient to increase the proportion of the charge separation material 106 contained in the photoelectric conversion layer 39.

[0136] The negative charge e remaining in the semiconductor-type carbon nanotube 105 and the positive charge h moving to the charge separation material 106 are not neutral macroscopically either. Therefore, the negative charge e and the positive charge h are respectively affected by the electric field represented by the arrow 502 brought about by the voltage applied between the counter electrode 38 and the pixel electrode 32 and start to move.

[0137] The negative charge e remaining in the semiconductor-type carbon nanotube 105 is affected by the electric field represented by the arrow 502 and moves inside the semiconductor-type carbon nanotube 105 to the pixel electrode 32 side. This movement is very fast. As shown by the arrow 504, the negative charge e moves to the position where the semiconductor-type carbon nanotube 105 contacts the pixel electrode 32 and is captured by the pixel electrode 32. That is, in the imaging device of the present application, the charge generated by photoelectric conversion is detected in a very short time.

[0138] On the other hand, the positive charge h moving to one molecule of the charge separation material 106 moves to the adjacent molecule of the charge separation material 106 by hopping conduction. Which molecule it hops to is determined by the intermolecular distance, the direction and intensity of the electric field. If the intermolecular distances are roughly equal, the molecule in the direction closer to the direction parallel to the electric field is selected as the hopping destination. If the electric field intensity is large, even if there are differences in the intermolecular distances, the probability that the molecule in the direction closer to the direction parallel to the electric field is selected as the hopping destination is higher. Therefore, as long as there is no extreme bias in the distribution of the intermolecular distances of the molecules of the charge separation material 106 and they are three-dimensionally distributed in the photoelectric conversion layer 39, as shown by the arrow 503, the positive charge h moves in the direction of the electric field macroscopically and is captured by the counter electrode 38. As a case where there is an extreme bias in the distribution of the intermolecular distances, for example, it is the case where the molecules of the charge separation material 106 are arranged only in a certain planar shape.

[0139] The carrier mobility in the charge separation material 106 is usually much smaller than that of the semiconductor-type carbon nanotube. In addition, the movement of the positive charge h between the molecules of the charge separation material 106 due to hopping is also slower than the carrier movement inside the semiconductor-type carbon nanotube 105.

[0140] In Figure 7In [the description], an example in which the negative charge e is trapped by the pixel electrode 32 is described, but the case in which the positive charge h is trapped by the pixel electrode 32 is also described in the same way. In this case, as the charge separation material 106, a material having an electron affinity larger than that of the semiconductor type carbon nanotube 105 can be used. Thereby, the charge separation material 106 extracts the negative charge e from the exciton. The positive charge h in the semiconductor carbon nanotube moves toward the pixel electrode 32.

[0141] In addition, in Figure 7 an example in which the negative charge e is directly trapped by the pixel electrode 32 from the molecule of the semiconductor type carbon nanotube 105 that generates the exciton is shown. However, the molecule of the semiconductor type carbon nanotube 105 does not need to be in direct contact with the pixel electrode 32. In the photoelectric conversion layer 39, two or more semiconductor type carbon nanotubes 105 are close to or in contact with each other, and as long as at least one of them is in contact with the pixel electrode 32, the charge can be trapped by the pixel electrode 32. In this case, the charge of the semiconductor type carbon nanotube 105 that is not in direct contact with the pixel electrode 32 moves as follows. First, it moves to another semiconductor type carbon nanotube 105 that is close to or in contact with it by hopping. By repeating this action, the charge moves to the semiconductor type carbon nanotube 105 that is in direct contact with the pixel electrode 32. Finally, the charge is trapped by the pixel electrode 32 from the semiconductor type carbon nanotube 105 that is in direct contact with the pixel electrode 32.

[0142] In addition, from the above description, it can be seen that in the photoelectric conversion layer 39, even if the charge separation material 106 is slightly included, one of the hole - electron pairs can be extracted from the semiconductor type carbon nanotube 105. The charge remaining in the carbon nanotube 105 moves rapidly between the semiconductor type carbon nanotubes 105 and can be trapped by the electrode 32. Therefore, the imaging device of the present application can exhibit the above effects according to the content of the charge separation material 106 in the photoelectric conversion layer 39.

[0143] Thus, according to the imaging device of the present embodiment, it includes a semiconductor type carbon nanotube having a high carrier mobility, and the charge moving in the semiconductor type carbon nanotube is trapped by the pixel electrode. Therefore, an imaging device capable of high-speed operation and capable of shooting at a high frame rate can be realized. For example, a distance image (Time - of - Flight) image sensor can be realized. In addition, the carbon nanotube has high chemical stability and its characteristics are not easily deteriorated. Therefore, it can be used in a wide temperature range, and an imaging device with high durability and reliability can be realized. Furthermore, there are carbon nanotubes with different wavelength sensitivity characteristics according to the difference in chirality. Therefore, it is easy to design the wavelength sensitivity characteristics. In addition, an imaging device capable of shooting images at multiple wavelengths can be realized.

[0144] In particular, in an organic thin film having absorption in the near-infrared region, due to the movement of organic molecules, the hole-electron pairs generated by photoelectric conversion are deactivated, or fluctuations occur in the transition energy levels. Therefore, in an imaging device, noise is likely to occur in the signal formed by the detected charges. In contrast, a carbon nanotube has a stable and rigid structure. Therefore, fluctuations are less likely to occur in the transition energy levels, and a signal formed by charges detected with a high S / N ratio can be obtained.

[0145] [5. Method of manufacturing an imaging device]

[0146] The imaging device 100 can be manufactured using a conventional semiconductor manufacturing process. In particular, when a silicon substrate is used as the semiconductor substrate 62, the imaging device 100 can be manufactured by using various silicon semiconductor processes.

[0147] First, as Figure 2 shown, using various semiconductor manufacturing techniques, the amplification transistor 42, the address transistor 44, and the reset transistor 46 are formed on the semiconductor substrate 62. Then, the interlayer insulating layers 63A to 63C, the contact plugs 65A, 65B, the wirings 66A, 68A, 68B, the plugs 67A to 67C, and the pixel electrode 32 are formed.

[0148] Then, if necessary, a hole blocking layer 103 is formed on the interlayer insulating layer 63C provided with the pixel electrode 32. When BCP is used in the hole blocking layer 103, the hole blocking layer 103 is formed by evaporation. When the hole blocking layer 103 is formed of a material soluble in a solvent, spin coating, spraying, or the like can be used.

[0149] Next, a photoelectric conversion layer 39 is formed. The photoelectric conversion layer 39 includes a semiconductor-type carbon nanotube 105 and a charge separation material 106. Among them, it is difficult to form the semiconductor-type carbon nanotube 105 by evaporation. Therefore, the semiconductor-type carbon nanotube 105 and the charge separation material 106 are separately prepared, mixed in a solvent, and attached to the interlayer insulating layer 63C by coating using spin coating, a doctor blade, or spraying. Alternatively, they can be attached to the interlayer insulating layer 63C by dispersing them in their respective solvents and coating them separately. In addition, the semiconductor-type carbon nanotube 105 can be attached to the interlayer insulating layer 63C by coating, and the charge separation material 106 can be formed on the interlayer insulating layer 63C by evaporation. When the semiconductor-type carbon nanotube 105 and the charge separation material 106 are arranged on the interlayer insulating layer 63C by different processes, the charge separation material 106 and the semiconductor-type carbon nanotube 105 can be alternately arranged on the interlayer insulating layer 63C, and at least one of them is arranged at least twice so that the semiconductor-type carbon nanotube 105 and the charge separation material 106 are dispersed in each other.

[0150] In order to disperse the semiconducting carbon nanotubes 105 into a solvent, polymers or surfactants can also be used as solubilizing agents. As long as these solubilizing agents do not have an adverse effect on the characteristics of the image sensor, they can also remain in the photoelectric conversion layer 39. Alternatively, the solubilizing agent can be removed only after the coating process.

[0151] The semiconducting carbon nanotubes 105 can be obtained by screening semiconducting carbon nanotubes from mass-produced carbon nanotubes. As methods for producing semiconducting carbon nanotubes, for example, the HiPCO method, the CoMoCAT method, the alcohol CVD method, and the arc discharge method can be cited. Alternatively, they can also be used after performing a chiral screening operation to increase the structural ratio of the desired chirality. These methods for screening semiconducting carbon nanotubes and chiral screening are described, for example, in (1) written by T. Tanaka et al., Applied Physics Express 2008, VOL.1, page 114001, (2) written by H. Liu et al., Nature Communications 2011, DOI: 10.1038 / ncomms1313, (3) written by A. Nish et al., Nature Technology 2007, VOL.2, pages 640 - 646, etc. By using semiconducting carbon nanotubes that have been subjected to chiral screening in this way, the mixing ratio of metallic carbon nanotubes can be suppressed to a lower level compared to the method of directly growing carbon nanotubes on a substrate. As a result, it is easier to achieve a camera device with good characteristics. In particular, according to the method described in the above-mentioned document (3), semiconducting carbon nanotubes with substantially the same diameter and different chiralities can be screened. Therefore, in order to realize a camera device that captures images in two or more specified wavelength ranges such as multi-spectral imaging, it is preferable to use semiconducting carbon nanotubes that have been screened for chirality by the method of document (3) or the like.

[0152] When manufacturing a camera device in which the spectral sensitivity characteristics of the photoelectric conversion layer 39 in each pixel are the same, large-area coating techniques such as spin coating and doctor blading can be used. When manufacturing a camera device that has different spectral sensitivity characteristics for each pixel, the following method can be used. First, prepare one or two or more dispersion liquids in which semiconducting carbon nanotubes with different chiralities are dispersed. Then, selectively eject each dispersion liquid by an inkjet method. Thereby, the photoelectric conversion layer 39 having different spectral sensitivity characteristics for each pixel can be formed without using a mask. It is also possible to form the photoelectric conversion layer 39 having different spectral sensitivity characteristics for each pixel by using a combination of spin coating, doctor blading, etc. and a mask.

[0153] For example, a semiconducting carbon nanotube with a relatively high ratio of chirality (8,0) can be used as the first pixel, and a semiconducting carbon nanotube with a relatively high ratio of chirality (7,2) can be used as the second pixel. In this case, the first pixel has a higher sensitivity to light with a wavelength of 780 nm than the second pixel, and the second pixel has a higher sensitivity to light with a wavelength of 820 nm than the first pixel. Therefore, if the respective images composed of the two types of pixels are compared, the redox degree of hemoglobin can be imaged. In addition, a semiconducting carbon nanotube with a relatively high ratio of chirality such as (12,4), (10,6), (13,0), etc. can be used as the first pixel, and a semiconducting carbon nanotube with a chirality such as (8,7) can be used as the second pixel. In this case, images at the missing wavelength of sunlight and wavelengths without missing in the vicinity thereof can be obtained.

[0154] The charge separation material 106 can be, for example, a commercially available material. Alternatively, it can also be disposed on the interlayer insulating layer 63C by evaporation. As described above, when the distribution density of the charge separation material 106 is increased on the pixel electrode 32 side and crosstalk between pixels is suppressed, it is preferable to first dispose the charge separation material 106 on the interlayer insulating layer 63C and dispose the semiconducting carbon nanotube 105 thereon.

[0155] Next, an electron blocking layer 101 is formed on the photoelectric conversion layer 39 by the same method as the hole blocking layer 103.

[0156] Next, the counter electrode 38 is formed. For example, ITO is formed by sputtering. Then, by forming the protective layer 72 and the microlens 74, the imaging device is completed. Thus, according to the manufacturing method of the imaging device of the present application, the photoelectric conversion unit 30 can be manufactured without utilizing the crystallinity of the surface of the support supporting the photoelectric conversion unit 30. In addition, in the formation of the photoelectric conversion unit 30, there is no process that requires treatment at a high temperature. Therefore, it can be stacked with a semiconductor substrate provided with a signal detection circuit, and a stacked imaging device can be realized.

[0157] (Second Embodiment)

[0158] In the second embodiment, the charge separation material extracts one of the hole-charge pairs generated in the carbon nanotube for use as a signal charge, which is different from the first embodiment. First, the inventor's understanding will be described.

[0159] Carbon nanotubes generally have a length of about several tens of nm to several mm. In contrast, the thickness of the photoelectric conversion layer of a photoelectric conversion element is usually from several nm to several hundred nm. Therefore, when carbon nanotubes are used as a photoelectric conversion material in a photoelectric conversion element, in the photoelectric conversion layer, the component ratio of the carbon nanotubes arranged parallel to the photoelectric conversion layer (in the direction perpendicular to the thickness direction) is longer than the component arranged in the thickness direction.

[0160] In order to make light incident on the photoelectric conversion layer and efficiently capture one of the generated hole-electron pairs as signal charges, it is preferable to apply a voltage to the photoelectric conversion layer. Figure 8 Schematically shows the carbon nanotube 500 located in the photoelectric conversion layer. There is a positive charge h at the position 501 of the carbon nanotube 500, and an electric field is applied from the outside in the direction of the arrow 502. When the charge h exists in free space, the charge h moves to the position 511 where it moves parallel along the arrow 502.

[0161] However, when the charge h exists in the carbon nanotube 500, the charge h first needs to go out of the carbon nanotube 500 to the outside. For this purpose, it is necessary to cross an energy barrier and follow a probabilistic phenomenon.

[0162] On the other hand, the electric field represented by the arrow 502 has an electric field component in the length direction 503 of the carbon nanotube 500. It is known that the charge movement along the length direction in the carbon nanotube 500 hardly encounters resistance, and the mobility in this direction is reported to be 10,000 cm 2 / (V·s) or more. Therefore, as long as the component parallel to the length direction of the carbon nanotube 500 of the electric field is not zero, the charge h is likely to move inside the carbon nanotube 500 and transfer to the position 521.

[0163] The imaging device is composed of a plurality of pixels and forms an image by generating a signal proportional to the amount of light incident on each pixel. When carbon nanotubes are used in the photoelectric conversion layer, for the above reasons, the charges generated by photoelectric conversion move inside the carbon nanotubes. Therefore, when the length of the carbon nanotube is larger than the size of the pixel 505, if the charge generated by photoelectric conversion moves inside the carbon nanotube, the pixel where light is incident and the pixel that detects the incident light may be different. Even when the length of the carbon nanotube is smaller than the size of the pixel 505, the same is true when the carbon nanotube is arranged across two pixels. As a result, crosstalk of the detection signals between pixels occurs, and the obtained image may be blurred without correctly reflecting the original light irradiation amount distribution.

[0164] Due to the small size (angle of view) of the imaging device or a large number of pixels due to high resolution of the imaging device, the problem becomes more significant as the pixel pitch becomes narrower. The imaging device of the present embodiment solves this problem and is particularly suitable for use in an imaging device with a narrow pixel pitch.

[0165] The overall structure of the imaging device according to this embodiment is the same as that of, for example, Figure 1 the imaging device according to the first embodiment shown. In addition, the device configuration of the imaging device according to this embodiment is also the same as that of, for example, Figure 2 the imaging device according to the first embodiment shown.

[0166] Next, the photoelectric conversion layer 39 of the photoelectric conversion unit 30 of the imaging device according to this embodiment will be described in detail. Figure 9 Schematically shows a cross-section of the photoelectric conversion unit 30 spanning multiple unit pixel units 20. In each unit pixel unit 20, the photoelectric conversion unit 30 includes a counter electrode 38, a pixel electrode 32, and a photoelectric conversion layer 39. The photoelectric conversion layer 39 is sandwiched between the counter electrode 38 and the pixel electrode 32.

[0167] From the viewpoint of suppressing the occurrence of leakage current, the photoelectric conversion layer 39 is not separated for each pixel, but is formed spanning multiple unit pixel units 20. The photoelectric conversion layer 39 includes semiconductor-type carbon nanotubes 105 and a charge separation material 106. At least a part of the carbon nanotubes 10 is arranged spanning multiple unit pixel units 20.

[0168] The structure, physical properties, etc. of the carbon nanotubes 105 are as described in the first embodiment. In addition, as the charge separation material 106, the materials described in the first embodiment can be used. That is, the charge separation material 106 can be a substance having a larger electron affinity than the semiconductor-type carbon nanotubes 105, or a substance having a smaller ionization potential than the semiconductor-type carbon nanotubes 105.

[0169] However, different from the first embodiment in which the charge remaining in the carbon nanotubes is moved to the pixel electrode and used as a signal charge, in the second embodiment, the charge extracted from the carbon nanotubes by the charge separation material is moved to the pixel electrode. For example, when using electrons as negative charges as signal charges, the voltage supply circuit 10 supplies a bias voltage to the counter electrode 38 so that the potential of the pixel electrode 32 is higher than the potential of the counter electrode 38. In addition, in this case, as the charge separation material 106, a substance having a larger electron affinity than the semiconductor-type carbon nanotubes 105 can be used. In this case, the electrons in the hole-electron pairs generated by the semiconductor-type carbon nanotubes 105 move to the conduction band 110 of the charge separation material 106 at a lower energy level. Therefore, holes remain in the valence band of the semiconductor-type carbon nanotubes.

[0170] Since the supplied voltage is determined to be a bias voltage that makes the potential of the pixel electrode 32 higher than the potential of the counter electrode 38, electrons move from the charge separation material 106 to the pixel electrode 32. In addition, in the case where holes, which are positive charges, are used as signal charges, the voltage supply circuit supplies a bias voltage to the counter electrode 38 in such a manner that the potential of the pixel electrode 32 becomes lower than the potential of the counter electrode 38. Further, in this case, a material having an ionization potential smaller than that of the semiconducting carbon nanotube 105 can be used as the charge separation material 106. In this case, since the charge separation material 106 is more stable when it is a positive ion, holes in the hole-electron pairs generated by the semiconducting carbon nanotube 105 move to the valence band of the charge separation material 106. Accordingly, electrons remain in the conductor of the semiconducting carbon nanotube 105. These holes move to the pixel electrode. Since the supplied voltage is determined to be a bias voltage that makes the potential of the pixel electrode 32 lower than the potential of the counter electrode 38, holes move from the charge separation material 106 to the pixel electrode 32.

[0171] In order to suppress problems caused by one-dimensional charge movement in the semiconducting carbon nanotube 105, it is preferable that the charge movement inside the charge separation material 106 is not one-dimensional. For example, in fullerenes, fullerene derivatives, and almost all low molecules, charges are restricted by molecular orbits. Accordingly, by applying an electric field from the outside, charge bias occurs within the molecule, but charge movement such as the formation of a macroscopic current does not occur. That is, there is no macroscopic charge movement freedom inside. In this case, the charge movement inside is zero-dimensional. Further, many conductive polymers have a one-dimensional chain-like molecular shape based on covalent bonds, and they have a structure in which they are intricately wound. In such conductive polymers, charge movement due to hopping conduction along the molecular chain and charge movement that moves between molecular chains at positions that are spatially close due to winding occur. The efficiency of these two types of charge movement does not have an extreme difference like that of carbon nanotubes. Accordingly, in the conductive polymer, charges move three-dimensionally.

[0172] In the photoelectric conversion layer 39, the semiconductor-type carbon nanotubes 105 and the charge separation material 106 are preferably dispersed in each other. As long as they are dispersed in each other, the distribution of the semiconductor-type carbon nanotubes 105 and the charge separation material 106 may not be uniform. For example, there may be a bias in the distribution in the thickness direction of the photoelectric conversion layer 39. Specifically, different from the first embodiment, the density of the semiconductor-type carbon nanotubes 105 in the thickness direction of the photoelectric conversion layer 39 may be higher on the counter electrode 38 side and lower on the pixel electrode 32 side. In addition, the density of the charge separation material 106 in the thickness direction of the photoelectric conversion layer 39 may be lower on the counter electrode 38 side and higher on the pixel electrode 32 side. Such a distribution is more preferable than the opposite density distribution because the charge separation material 106 extracts the charge to be captured by the pixel electrode 32 from the semiconductor-type carbon nanotubes. The thickness of the photoelectric conversion layer 39 is, for example, several tens of nm or more and several hundreds of nm or less. In addition, the photoelectric conversion layer 39 may further include an n-type semiconductor and a p-type semiconductor.

[0173] Similar to the first embodiment, the photoelectric conversion unit 30 may further include a hole blocking layer 103 and an electron blocking layer 101. The materials described in the first embodiment may be used for the hole blocking layer 103 and the electron blocking layer 101.

[0174] Refer to Figure 10 Describe the detection of incident light in the photoelectric conversion layer 39. Figure 10 It is a schematic diagram showing the positional relationship between the arrangement of the semiconductor-type carbon nanotubes 105 and the charge separation material 106 located in the photoelectric conversion layer 39 and the pixel electrode 32 of the unit pixel unit. The semiconductor-type carbon nanotubes 105 are arranged across two unit pixel units 20. In the following example, electrons are used as signal charges in the same way as in the first embodiment, but different from the first embodiment, the charge separation material 106 is a substance having a larger electron affinity than the semiconductor-type carbon nanotubes 105. In addition, in Figure 10 A bias voltage is supplied to the counter electrode 38 so that the potential of the pixel electrode 32 is higher than the potential of the counter electrode 38. Therefore, an electric field is generated in the direction indicated by the arrow 502.

[0175] Similar to the first embodiment, if photons (not shown) are absorbed by the semiconductor-type carbon nanotubes 105, a positive charge (hole) h and a negative charge (electron) e are generated approximately at this position 501. The generated positive charge h and negative charge e interact with each other by gravitational force to form a state called an exciton. Since an exciton is macroscopically electrically neutral, the position of the exciton is not affected by the applied electric field and only diffuses and moves smoothly.

[0176] If the exciton reaches a position close to the charge separation material 106, separation of the charges of the exciton occurs. Specifically, the negative charge e is extracted by the charge separation material 106, and one of the charges moves into one molecule of the charge separation material 106 while the other charge remains in the semiconducting carbon nanotube 105. In Figure 7 the example shown, since the charge separation material 106 has a larger electron affinity than the semiconducting carbon nanotube 105, the negative charge e is extracted. As a result, a positive charge remains in the semiconducting carbon nanotube 105.

[0177] Separation of the charges occurs at a position where the semiconducting carbon nanotube 105 and the charge separation material 106 are close to each other. Therefore, if there is one or more molecules of the charge separation material 106 in the unit pixel cell 20 around one molecule of the semiconducting carbon nanotube 105, charge separation occurs in the pixel where the exciton is generated. In order for the generation of the exciton and the charge separation to occur in the same unit pixel cell, it is sufficient to increase the proportion of the charge separation material 106 contained in the photoelectric conversion layer 39.

[0178] The positive charge h remaining in the semiconducting carbon nanotube 105 and the negative charge e that has moved into the charge separation material 106 are not neutral macroscopically either. Therefore, the positive charge h and the negative charge e are each affected by the electric field represented by the arrow 502 caused by the voltage applied between the counter electrode 38 and the pixel electrode 32 and start to move.

[0179] The positive charge h remaining in the semiconducting carbon nanotube 105 moves not only in the direction of the arrow 502 but also strongly affected by the electric field component along the extending direction 503 of the semiconducting carbon nanotube 105 due to the anisotropy of the electrical conduction of the carbon nanotube. As a result, the positive charge h moves in the extending direction of the semiconducting carbon nanotube 105 and reaches the position 521. This positive charge h is trapped by the counter electrode 38 (not shown). Since the counter electrode 38 is formed across multiple pixels, the positive charge h can be trapped at any position.

[0180] On the other hand, the negative charge e that has moved into one molecule of the charge separation material 106 moves to an adjacent molecule of the charge separation material 106 by hopping conduction. To which molecule it hops is determined by the distance between the molecules, the direction and strength of the electric field. If the distances between the molecules are approximately equal, the molecule in the direction closer to being parallel to the electric field is selected as the hopping destination. Further, if the strength of the electric field is large, even if there is a difference in the distances between the molecules, the probability that the molecule in the direction closer to being parallel to the electric field is selected as the hopping destination is high.

[0181] Therefore, if there is no extreme bias in the distribution of the intermolecular distances of the charge separation material 106 and it is three-dimensionally distributed within the photoelectric conversion layer 39, the negative charge e moves macroscopically in the direction of the electric field. As a case where there is an extreme bias in the distribution of the intermolecular distances, for example, it is the case where the molecules of the charge separation material 106 are arranged only in a certain planar shape. As a result, it is trapped by the pixel electrode 32 within the unit pixel cell 20 where excitons are generated. That is, the pixel where light is incident coincides with the pixel that detects the incident light.

[0182] Even if the charge movement inside the charge separation material 106 is three-dimensional, the charge moves in the direction of the electric field macroscopically. In addition, by increasing the potential difference applied between the counter electrode 38 and the pixel electrode 32 and increasing the intensity of the electric field, the negative charge can be more reliably detected by the pixel where excitons are generated.

[0183] In Figure 10 an example where the negative charge e is trapped by the pixel electrode 32 is described, and the case where the positive charge h is trapped by the pixel electrode 32 can be similarly described. In addition, in Figure 10 one semiconductor-type carbon nanotube 105 is shown, but in the photoelectric conversion layer 39, two or more semiconductor-type carbon nanotubes 105 may be close to each other. In this case, in addition to the charge separation between the semiconductor-type carbon nanotube 105 and the charge separation material 106 in (i) above, and the charge movement between the molecules of the charge separation material 106 in (ii) above, charge separation between two or more semiconductor-type carbon nanotubes 105 in (iii) and charge movement from the semiconductor-type carbon nanotube 105 to the charge separation material 106 in (iv) may also occur. However, between semiconductor-type carbon nanotubes 105 with the same chirality, the electron affinity and ionization potential are equal. In addition, from the viewpoint of electron affinity or ionization potential, the case where the positive charge or negative charge to be detected as a signal moves from the semiconductor-type carbon nanotube 105 to the charge separation material 106 is energetically favorable. Therefore, it is not easy for the positive charge or negative charge to move from the charge separation material 106 to the semiconductor-type carbon nanotube 105. Therefore, the charge movements such as those shown in (iii) and (iv) are energetically less favorable than those in (i) and (ii) and are not likely to occur.

[0184] In addition, according to the above description, it can be seen that if even a little charge separation material 106 is included in the photoelectric conversion layer 39, the charge to be detected as a signal within the semiconductor-type carbon nanotube 105 can be extracted from the semiconductor-type carbon nanotube 105, and the charge to be detected as a signal is moved toward the pixel electrode 32 according to the electric field brought about by the voltage applied between the counter electrode 38 and the pixel electrode 32. Therefore, the imaging device of the present application can achieve the above effects according to the content of the charge separation material 106 in the photoelectric conversion layer 39.

[0185] Thus, according to the present embodiment, in addition to the effects described in the first embodiment, it is also possible to implement an imaging device that can suppress the mixing of detected charges between pixels and obtain a high-definition image, or an imaging device with a small pixel size.

[0186] The imaging device of the present embodiment, like the imaging device of the first embodiment, can be manufactured using ordinary semiconductor manufacturing processes. In particular, when a silicon substrate is used as the semiconductor substrate 62, the imaging device can be manufactured by utilizing various silicon semiconductor processes.

[0187] In addition, in the above embodiment, an example is described in which the amplification transistor 42, the address transistor 44, and the reset transistor 46 are each an N-channel MOS. However, the transistors of the embodiments of the present application are not limited to N-channel MOS. The amplification transistor 42, the address transistor 44, and the reset transistor 46 may also be P-channel MOS. In addition, it is not necessary for all of them to be unified into either N-channel MOS or P-channel MOS. As the transistor, in addition to the FET, a bipolar transistor may also be used.

[0188] In addition, in the above embodiment, an imaging device having a form in which charges to be detected by the pixel electrode are trapped is described. However, the imaging device may instead include an impurity diffusion region provided on the semiconductor substrate in place of the pixel electrode, and the impurity diffusion region traps one of the hole-electron pairs generated by the photoelectric conversion layer as the charge to be detected.

[0189] Industrial Applicability

[0190] The imaging device of the present application can be suitably used in various imaging devices capable of obtaining images in the visible region and the near-infrared region. In particular, it can be suitably used in imaging devices with high-speed operation, high frame rate, and / or high definition, high pixel count, and small pixel size.

[0191] Reference Numeral Explanation

[0192] 10 Voltage supply circuit

[0193] 20 Unit pixel unit

[0194] 22 Accumulation control line

[0195] 23 Power supply line

[0196] 24 Vertical signal line

[0197] 25 Address signal line

[0198] 26 Reset signal line

[0199] 27 Feedback line

[0200] 30 Photoelectric conversion section

[0201] 32 Pixel electrode

[0202] 38 Counter electrode

[0203] 39 Photoelectric conversion layer

[0204] 40 Signal detection circuit

[0205] 41 Charge storage node

[0206] 42 Amplification transistor

[0207] 42g, 44g, 46g Gate insulating layer

[0208] 42e, 44e, 46e Gate electrode

[0209] 44 Address transistor

[0210] 46 Reset transistor

[0211] 52 Vertical scanning circuit

[0212] 54 Horizontal signal readout circuit

[0213] 56 Column signal processing circuit

[0214] 58 Load circuit

[0215] 59 Inverting amplifier

[0216] 61 Substrate

[0217] 62 Semiconductor substrate

[0218] 62a - 62e Impurity regions

[0219] 62s Element isolation region

[0220] 63A - 63C Interlayer insulating layers

[0221] 65A, 65B Contact plugs

[0222] 66A, 68A, 68B Wiring

[0223] 67A - 67C Plugs

[0224] 72 Protective layer

[0225] 74 Microlens

[0226] 100 Imaging device

[0227] 101 Electron blocking layer

[0228] 103 Hole blocking layer

[0229] 105 Semiconducting carbon nanotube

[0230] 106 Charge separation material

[0231] 110 Conduction band

[0232] 111 Valence band

[0233] 113 Vacuum level

[0234] 150 Semiconducting carbon nanotube

[0235] 196 Charge separation material

[0236] Positions 501, 511, 512

Claims

1. An imaging device includes a plurality of pixels arranged one-dimensionally or two-dimensionally, characterized in that: Each pixel includes: A first electrode electrically connected among the plurality of pixels; A charge trapping portion divided for each of the pixels; and A photoelectric conversion layer located between the first electrode and the charge trapping portion and connected among the plurality of pixels; The photoelectric conversion layer includes semiconducting carbon nanotubes and a first substance having an electron affinity greater than that of the semiconducting carbon nanotubes; The charge trapping portion traps positive charges; At least one of the semiconducting carbon nanotubes is arranged across two pixels.

2. The imaging device according to claim 1, characterized in that: The first substance is a molecule having a fullerene skeleton.

3. The imaging device according to claim 1, characterized in that: It further includes a voltage supply circuit electrically connected to the first electrode; The voltage supply circuit supplies a voltage to the first electrode so that the potential of the charge trapping portion is lower than the potential of the first electrode.

4. An imaging device includes a plurality of pixels arranged one-dimensionally or two-dimensionally, characterized in that: Each pixel includes: A first electrode electrically connected among the plurality of pixels; A charge trapping portion divided for each of the pixels; and A photoelectric conversion layer located between the first electrode and the charge trapping portion and connected among the plurality of pixels; The photoelectric conversion layer includes semiconducting carbon nanotubes and a first substance having an ionization potential smaller than that of the semiconducting carbon nanotubes; The charge trapping portion traps negative charges; At least one of the semiconducting carbon nanotubes is arranged across two pixels.

5. The imaging device according to claim 4, characterized in that: It further includes a voltage supply circuit electrically connected to the first electrode; The voltage supply circuit supplies a voltage to the first electrode so that the potential of the charge trapping portion is higher than the potential of the first electrode.

6. The imaging device according to claim 1 or 4, characterized in that: It further includes a semiconductor substrate supporting the photoelectric conversion layer; Each pixel further includes a charge detection transistor provided on the semiconductor substrate and electrically connected to the charge trapping portion.

7. The imaging device according to claim 1 or 4, characterized in that: In the photoelectric conversion layer, the first substance and the semiconducting carbon nanotubes are dispersed in each other.

8. The imaging device according to claim 6, characterized in that: The charge trapping portion is an impurity diffusion region formed in the semiconductor substrate.

9. The imaging device according to claim 6, characterized in that: The charge trapping portion is a second electrode located on the semiconductor substrate.

10. The imaging device according to claim 1 or 4, characterized in that: The chirality of the semiconducting carbon nanotubes is controlled so that the photoelectric conversion layer has a specific resonance wavelength.

11. The imaging device according to claim 1 or 4, characterized in that: Two or more of the semiconducting carbon nanotubes are in contact with each other.

12. The imaging device according to claim 9, characterized in that: The density of the semiconductor-type carbon nanotubes is lower on the first electrode side than on the second electrode side described above.

13. The imaging device according to claim 1 or 4, characterized in that The photoelectric conversion layer has a double-layer structure, and the double-layer structure has a first layer of the semiconductor-type carbon nanotubes and a second layer of the first substance.

14. The imaging device according to claim 1 or 4, characterized in that The photoelectric conversion layer has a resonance wavelength in the near-infrared region.

15. The imaging device according to claim 14, characterized in that The chirality of the semiconductor-type carbon nanotubes is controlled so that the photoelectric conversion layer has the resonance wavelength in the near-infrared region.

16. A method of using the imaging device according to claim 1, characterized in that, comprising the following steps: incident light on the photoelectric conversion layer; and applying a voltage to the first electrode so that the potential of the charge trapping portion is lower than the potential of the first electrode.

17. A method using the imaging device according to claim 4, characterized in that, comprising the following steps: incident light on the photoelectric conversion layer; and applying a voltage to the first electrode so that the potential of the charge trapping portion is higher than the potential of the first electrode.

Images