Photodetector

Abstract

To provide a photodetector capable of reducing the crosstalk between channels.SOLUTION: A photodetector 1 comprises: a tabular incident surface plate 2 on which a photoelectric surface 2s for emitting photoelectrons in accordance with incident light is formed; and a semiconductor element 10 for detecting the photoelectrons emitted from the photoelectric surface 2s, the semiconductor element being disposed to face the photoelectric surface 2s. The semiconductor element 10 has a first portion 11 having an electron incident surface 11s facing the photoelectric surface 2s, the electron incident surface including a plurality of channels ch that are arranged separated from each other. A distance b between the photoelectric surface 2s and the electron incident surface 11s, an interval Δch between the channels ch, and a voltage V applied between the photoelectric surface 2s and the electron incident surface 11s satisfy the formula (1): distance b [mm] / interval Δch [mm]<14.4×voltage V [kV]+60.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a photodetector.

Background Art

[0002] Patent Document 1 describes an electron tube. This electron tube includes an input faceplate provided on one side of a side tube and having a photocathode that emits electrons in response to incident light, a stem provided on the other side of the side tube and defining a vacuum region together with the input faceplate, and a semiconductor element fixed to the vacuum side of the stem and having an electron incident portion for injecting electrons emitted from the photocathode. The semiconductor element is configured as a back-illuminated semiconductor element in which the front surface is positioned on the stem side, the back surface is positioned on the input faceplate side, and the electron incident portion is formed in a thin plate shape with respect to a peripheral portion disposed on the outer periphery of the electron incident portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Currently, in a photodetector such as the electron tube described in Patent Document 1, for the purpose of detecting a plurality of wavelength components spectrally separated by, for example, a spectroscope, there is a requirement to configure an electron incident portion including a plurality of channels for the semiconductor element. On the other hand, since the trajectory of electrons from the photocathode toward the electron incident portion has a certain spread, a configuration for suppressing crosstalk between channels is required.

[0005] An object of the present disclosure is to provide a photodetector capable of suppressing crosstalk between channels.

Means for Solving the Problems

[0006] The photodetector according to the present disclosure is a "photodetector comprising: an incident panel on which a photocathode for emitting photoelectrons in response to incident light is formed; and a semiconductor element disposed to face the photocathode along a first direction and for detecting the photoelectrons emitted from the photocathode, the semiconductor element having a first portion having an electron incident surface including a plurality of channels arranged while being spaced apart from each other along a second direction intersecting the first direction, the incident panel being flat, with the distance between the photocathode and the electron incident surface in the first direction being distance b, the interval between the channels in the second direction being interval Δch, and when the voltage applied between the photocathode and the electron incident surface is voltage V, satisfying the following formula (1)". Distance b [mm] / Interval Δch [mm] < 14.4 × Voltage V [kV] + 60…(1)

[0007] In this photodetector, the semiconductor element for detecting the photoelectrons emitted from the photocathode has a first portion having an electron incident surface including a plurality of channels arranged while being spaced apart from each other. And in this photodetector, with the distance between the photocathode and the electron incident surface being distance b, the interval between the channels in the arrangement direction of the channels (second direction) being interval Δch, and the voltage applied between the photocathode and the electron incident surface being voltage V, the above formula (1) is satisfied. Thereby, the interval Δch between the channels is appropriately set according to the spread of the electron trajectories according to the voltage V between the photocathode and the electron incident surface and the distance b from the photocathode to the electron incident surface, so that crosstalk between the channels is suppressed. In particular, in this photodetector, since the incident panel is flat, it is easy to manufacture and it is easy to set the distance b between the photocathode and the electron incident surface so as to satisfy each formula.

[0008] Here, in a photodetector such as the electron tube described in Patent Document 1 above, in the semiconductor element, when a relatively thick portion (the above-mentioned peripheral portion) is formed around the electron incident portion, there is a possibility that distortion may occur in the equipotential surface between the photocathode and the electron incident portion from the electron incident portion to the peripheral portion. In that case, the electron collection efficiency of the channel in the region where the equipotential surface is distorted (for example, the channel near the peripheral portion) may be lower than that of the channel in the region where the equipotential surface is not distorted (for example, the channel other than near the peripheral portion). Therefore, even when distortion occurs in the equipotential surface near the peripheral portion, it is desirable to suppress a decrease in the electron collection efficiency of the channel located on the peripheral portion side.

[0009] Therefore, the photodetector according to the present disclosure may be the photodetector element described in [1] above, which "[2] has a second portion provided on both end sides of the electron incident surface at least in the second direction and formed thicker than the first portion by protruding toward the photocathode side from the electron incident surface, and when the distance from the end of the electron incident surface on one side in the second direction to the end of the second portion is defined as distance e and the distance from the end of the outermost channel on one side in the second direction to the start of the second portion is defined as distance w, satisfies the following formula (2) or the following formula (3)". Distance b [mm] / 4 < Distance e [mm] < Distance b [mm]... (2) Distance b [mm] < Distance e [mm], and Distance w [mm] > 0.2 [mm]... (3)

[0010] In this photodetector, the semiconductor element has a second portion provided on both end sides of the electron incident surface at least in the channel arrangement direction and formed thicker than the first portion by protruding toward the photocathode side from the electron incident surface. And when this photodetector defines the distance from the end of the electron incident surface to the end of the second portion as distance e and the distance from the end of the outermost channel to the start of the second portion as distance w, it satisfies the above formula (2) or the above formula (3). Thereby, even when distortion occurs from the electron incident surface to the second portion with respect to the equipotential surface between the photocathode and the electron incident portion, a decrease in the electron collection efficiency in the outermost channel is suppressed.

[0011] The photodetector according to the present disclosure may be "[3] the photodetector described in [1] or [2] above that satisfies the following formula (4)". In this case, crosstalk between channels can be surely suppressed. Distance b [mm] / interval Δch [mm] < 13.2 × voltage V [kV] + 55…(4)

[0012] The photodetector according to the present disclosure may be "[4] the photodetector described in [3] above that satisfies the following formula (5)". In this case, crosstalk between channels can be more surely suppressed. Distance b [mm] / interval Δch [mm] < 12.4 × voltage V [kV] + 51.5…(5)

[0013] The photodetector according to the present disclosure may be "[5] the photodetector described in [4] above that satisfies the following formula (6)". In this case, crosstalk between channels can be even more surely suppressed. Distance b [mm] / interval Δch [mm] < 12 × voltage V [kV] + 50…(6)

[0014] The photodetector according to the present disclosure may be "[6] the photodetector according to any one of [1] to [5] above, comprising a side tube sealed at one end by the incident panel, a stem sealing the other end of the side tube, and an insulating base member provided on the stem, wherein the semiconductor element is provided on the base member such that the electron incident surface faces the photoelectric surface side". In this case, by setting the dimensions of each part of the side tube, the incident panel, and the base member, it becomes possible to realize, for example, a distance b that satisfies the above formula.

[0015] The photodetector according to the present disclosure may be "[7] the photodetector according to any one of [1] to [6] above, provided with an insulating film having a thickness of 100 nm or less on at least the surface facing the photoelectric surface in the semiconductor element". In this case, the insulating film formed at least on the surface of the semiconductor element suppresses the return of the gas ionized by the photoelectrons being implanted into the semiconductor element to the photoelectric surface (ion feedback).

Advantages of the Invention

[0016] According to the present disclosure, it is possible to provide a photodetector capable of suppressing crosstalk between channels.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

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Figure 5

Figure 6

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Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0018] Hereinafter, a photodetector according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements may be denoted by the same reference numerals, and redundant descriptions may be omitted. In each figure, a rectangular coordinate system may be shown that consists of an axis defining a first direction D1, an axis defining a second direction D2 intersecting the first direction D1, and an axis defining a third direction intersecting the first direction D1 and the second direction D2.

[0019] FIG. 1 is a schematic cross-sectional view of the photodetector according to this embodiment. FIG. 2 is a top view showing a part of the photodetector shown in FIG. 1. In FIG. 1, hatching is omitted. The photodetector 1 shown in FIGS. 1 and 2 is, for example, an HPD (Hybrid Photo Detector), and can be used, for example, in a fluorescence microscope, a flow cytometer, a time-resolved measurement device, etc.

[0020] The photodetector 1 includes an incident panel 2, a photocathode 2s, a side tube 3, a stem 4, a base member 5, a pin 6, an insulating film 7, and a semiconductor element 10. The incident panel 2 includes a front surface 2a and a back surface 2b on the side opposite to the front surface 2a. It is made of a light-transmissive material such as glass, for example, and transmits the light incident from the front surface 2a toward the back surface 2b. The incident panel 2 is formed, for example, in a circular flat plate shape (i.e., a disk shape). That the incident panel 2 is in a flat plate shape means that, for the direction (first direction D1) from the front surface 2a to the back surface 2b of the incident panel 2, for example, the thickness of a relatively thick portion is within the range of about 130% of the thickness of a relatively thin portion.

[0021] The photocathode 2s is provided on the back surface 2b of the incident panel 2. The photocathode 2s includes a photoelectric conversion layer made of a thin film of a compound semiconductor such as GaAs, and emits photoelectrons in response to the incident light that has passed through the incident panel 2.

[0022] The side tube 3 is formed into a tubular shape (here, a circular tubular shape) with both ends open by an insulating material such as ceramic. One end of the side tube 3 is sealed by the incident surface plate 2. The stem 4 is formed into a plate shape (here, a circular plate shape) by an insulating material such as ceramic and seals the other end of the side tube 3. Thereby, a vacuum region can be formed in the side tube 3. A metal member that also serves as a connecting member made of, for example, Kovar is interposed between one end of the side tube 3 and the incident surface plate 2, and between the other end of the side tube 3 and the stem 4. A voltage can be applied through the metal member such that the stem 4 side becomes the GND potential with respect to the photoelectric surface 2s (the photoelectric surface 2s has a negative potential and the stem 4 side becomes the ground potential).

[0023] The base member 5 is provided on the stem 4 so as to be located inside the side tube 3. The base member 5 has a top surface 5a that is a surface facing the photoelectric surface 2s, and is formed into a rectangular parallelepiped block shape that protrudes convexly from the stem 4 toward the photoelectric surface 2s by an insulating material such as ceramic. A plurality (for example, the same number as the channels ch described later) of pins 6 are provided penetrating the base member 5 so that each can output an electrical signal detected by the semiconductor element 10 to the outside. For example, one end of the pin 6 reaches the surface (top surface 5a) of the base member 5 on the side opposite to the stem 4, and the other end of the pin 6 protrudes outside the side tube 3 from the surface of the base member 5 on the stem 4 side. Note that the base member 5 may be formed integrally with the stem 4, and the pin 6 and the semiconductor element 10 may be electrically connected via other conductive members such as wiring.

[0024] The semiconductor element 10 is for detecting the photoelectrons emitted from the photocathode 2s. The semiconductor element 10 is disposed on the top surface 5a of the base member 5 so as to face the photocathode 2s along the first direction D1. More specifically, the semiconductor element 10 includes a back surface 10r and a front surface 10s, and is provided on the top surface 5a of the base member 5 such that the back surface 10r (i.e., the electron incident surface 11s described later) faces the photocathode 2s (such that the front surface 10s faces the top surface 5a side of the base member 5). The semiconductor element 10 is electrically connected to the pin 6 by bump connection as an example. The semiconductor element 10 is, for example, an AD (Avalanche diode). In this case, the semiconductor element 10 receives the incidence of photoelectrons from the photocathode 2s, causes multiplication by electron injection, and causes further multiplication by avalanche multiplication. Note that the semiconductor element 10 may be a PD (Photo diode), a SiPM (Silicon photomultiplier), or a SPAD (Single photon avalanche diode). Further, in the present embodiment, a back-illuminated semiconductor element is used as the semiconductor element 10.

[0025] The semiconductor element 10 has a first portion 11 and a second portion 12. The first portion 11 has an electron incident surface 11s which is a surface facing the optoelectronic surface 2s. The electron incident surface 11s includes a plurality of channels ch arranged while being spaced apart from each other along a second direction D2 intersecting the first direction D1. In other words, the electron incident surface 11s is a photoelectron detection surface in the semiconductor element 10, and includes a sensitivity region which is a plurality of channels ch, and an insensitive region surrounding the periphery of each channel ch. Note that the insensitive region includes a partition portion for adjacent channels ch (a portion corresponding to a region indicated by an interval Δch described later), and a region provided between the outermost channel ch and the second portion 12 described later (a region corresponding to a region indicated by a distance w described later). The semiconductor element 10 detects photoelectrons in each of the plurality of channels ch. The second portion 12 is provided at least on both end sides of the electron incident surface 11s in the second direction D2. In the present embodiment, the second portion 12 is formed in a rectangular frame shape so as to surround the electron incident surface 11s when viewed from the first direction D1. The second portion 12 is formed thicker than the first portion 11 by protruding toward the optoelectronic surface 2s side from the electron incident surface 11s. A potential is applied between the optoelectronic surface 2s and the electron incident surface 11s such that photoelectrons emitted from the optoelectronic surface 2s travel toward the electron incident surface 11s with a desired acceleration. In the present embodiment, a voltage is applied such that the electron incident surface 11s side is at the GND potential (such that the optoelectronic surface 2s has a negative potential and the electron incident surface 11s side has a ground potential).

[0026] The insulating film 7 is provided on at least the surface of the semiconductor element 10 facing the photoelectric surface 2s. In the present embodiment, the insulating film 7 is formed on the surfaces of the semiconductor element 10, the base member 5, the stem 4, and the pin 6. The insulating film 7 is preferably formed to a thickness of about 100 nm or less, for example, by a metal oxide (e.g., aluminum oxide), and in the present embodiment, it is formed to a thickness of about 30 nm or less. Thereby, the insulating film 7 does not affect the incidence of photoelectrons on the electron incident surface 11s and the electrical connection of the pin 6. The insulating film 7 can be formed, for example, by performing film formation by ALD (Atomic Layer Deposition) on a unit composed of the semiconductor element 10, the base member 5, the stem 4, and the pin 6.

[0027] Subsequently, the relationship between the respective parts of the photodetector 1 will be described. FIG. 3 is a partially enlarged view of the photodetector shown in FIG. 1. FIG. 4 is a partially enlarged view of the semiconductor element shown in FIG. 2. FIG. 4(a) is an enlarged perspective view of region A1 in FIG. 2, and FIG. 4(b) is a schematic enlarged cross-sectional view of region A2 in FIG. 2. In FIG. 4(b), an equipotential surface Sv corresponding to the voltage applied between the photoelectric surface 2s and the electron incident surface 11s is shown.

[0028] As shown in FIGS. 3 and 4, in the following description, the distance between the photoelectric surface 2s and the electron incident surface 11s in the first direction D1 is defined as distance b, and the interval between the channels ch in the second direction D2 is defined as interval Δch. Also, the voltage applied between the photoelectric surface 2s and the electron incident surface 11s is defined as voltage V, the distance from the end of the electron incident surface 11s on one side in the second direction D2 (the end on one side in the second direction D2) to the end of the second portion 12 (the end on one side in the second direction D2) is defined as distance e, and the distance from the end of the outermost (the outermost end) channel ch on one side in the second direction D2 (the end on one side in the second direction D2) to the start of the second portion 12 (the end on the electron incident surface 11s side of the portion of the first portion 11 located on one side in the second direction D2) is defined as distance w.

[0029] Note that the distance w is the distance from the end of the outermost channel ch (the end on one side in the second direction D2) to the rising part of the second portion 12. Also, when a member (such as a wiring) having the same potential (or substantially the same potential) as the electron incident surface 11s is provided further outside the end of the second portion 12, the distance e can be the distance to that end. Furthermore, regarding the distance e and the distance w, they may be set in the same manner for the other side in the second direction D2, or when the channels ch are arranged along the third direction D3, they may be set in the same manner for the third direction D3. Also, the channel ch is an electron collection part which is a semiconductor region inside the semiconductor element 10, and the interval Δch is the interval between the electron collection parts. The interval Δch may be the distance between guard rings when guard rings, which are another semiconductor region, are formed at the edges of the electron collection parts.

[0030] In the photodetector 1, the distance b, the voltage V, the distance e, and the distance w set as described above satisfy a certain relationship from the viewpoints of suppressing crosstalk between the channels ch and suppressing a decrease in the electron collection efficiency of the outermost channel ch.

[0031] FIG. 5 is a graph showing the relationship between the voltage V and the distance b when the crosstalk between the channels is 0% for each value of the interval Δch between the channels. FIG. 6 is a graph showing the relationship between the voltage V and the distance b when the interval Δch between the channels is 50 μm for each value of the crosstalk. Further, FIG. 7 is a graph showing the relationship between the voltage V and the distance b when the interval Δch between the channels is 100 μm for each value of the crosstalk. Note that the crosstalk between the channels ch means that the photoelectrons emitted from the region facing one channel ch in the first direction D1 on the photoelectric surface 2s enter another channel ch adjacent to the one channel ch.

[0032] As shown in Fig. 5, when suppressing the crosstalk between channels ch to 0%, it was found that there is a certain relationship between the voltage V and the distance b for each interval Δch. Also, as shown in Figs. 6 and 7, the relationship between the voltage V and the distance b shown in Fig. 5 has a similar tendency even when the allowable crosstalk is set to each value from 0% to 20%. Therefore, in the photodetector 1, when suppressing the crosstalk to about 20%, the following formula (1) is satisfied. In other words, in the photodetector 1, by satisfying the following formula (1), the crosstalk between channels ch can be suppressed to about 20%. Distance b [mm] / Interval Δch [mm] < 14.4 × Voltage V [kV] + 60…(1)

[0033] On the other hand, Fig. 8 is a graph showing the relationship between the distance b normalized by the distance e and the collection efficiency of the outermost channel for each distance e. As shown in Fig. 8, even when the distance e is 1 [mm], which is the case where the condition of the collection efficiency is the most severe, it was confirmed that a collection efficiency of 80% or more can be obtained in the range where the distance b is about 1 [mm] to 4 [mm]. Therefore, in the photodetector 1, when the collection efficiency of the electrons in the outermost channel ch is 80% or more and the distance e is smaller than the distance b, the following formula (2) is satisfied. In other words, in the photodetector 1, by satisfying the following formula (2), the collection efficiency of the electrons in the outermost channel ch is ensured to be 80% or more. Distance b [mm] / 4 < Distance e [mm] < Distance b [mm]…(2)

[0034] On the other hand, Fig. 9 is a graph showing the relationship between the distance e and the collection efficiency when the distance e is larger than the distance b for each value of the distance w. In Fig. 9, each case where the distance W = 0 [mm], 0.2 [mm], 0.4 [mm], 0.5 [mm], 0.6 [mm], 0.8 [mm], 1 [mm] is shown. As shown in Fig. 9, in the photodetector 1, when the distance e is larger than the distance b, when the distance w is 0.2 [mm] or more, a collection efficiency of 95% or more is obtained for each distance e. Therefore, in the photodetector 1, by satisfying the following formula (3), a decrease in the collection efficiency of electrons is suppressed. Distance b [mm] < distance e [mm], and distance w [mm] > 0.2 [mm]…(3)

[0035] Note that the above formula (1) is required to suppress the crosstalk between channels ch to about 20%. Therefore, in the photodetector 1, in order to suppress the crosstalk between channels ch lower, the following formulas (4) to (6) can be satisfied. In the photodetector 1, by satisfying the following formula (4), the crosstalk can be suppressed to about 10%, by satisfying the following formula (5), the crosstalk can be suppressed to about 3%, and by satisfying the following formula (6), the crosstalk can be suppressed to about 0%. Distance b [mm] / interval Δch [mm] < 13.2 × voltage V [kV] + 55…(4) Distance b [mm] / interval Δch [mm] < 12.4 × voltage V [kV] + 51.5…(5) Distance b [mm] / interval Δch [mm] < 12 × voltage V [kV] + 50…(6)

[0036] Note that the distance b can be, for example, 0 [mm] to 20 [mm]. The distance b is preferably 0.5 [mm] to 10 [mm], and more preferably 1 [mm] to 6 [mm]. The voltage V can be, for example, 0.1 [kV] to 8 [kV]. The voltage V is preferably 1 [kV] to 7 [kV], and more preferably 2 [kV] to 6 [kV]. The interval Δch can be, for example, 0.01 [mm] to 0.5 [mm]. The interval Δch is preferably 0.01 [mm] to 0.3 [mm], and more preferably 0.03 [mm] to 0.2 [mm].

[0037] The distance e can be, for example, from 0.1 [mm] to 10 [mm]. The distance e is preferably from 1 [mm] to 5 [mm], and more preferably from 1 [mm] to 3 [mm]. The distance w can be, for example, from 0 [mm] to 10 [mm]. The distance w is preferably from 0 [mm] to 1 [mm], and more preferably from 0 [mm] to 0.3 [mm]. The crosstalk can be about 20%, preferably about 10%, and more preferably about 3% or about 0%.

[0038] As described above, in the photodetector 1 according to the present embodiment, the semiconductor element 10 for detecting the photoelectrons emitted from the photoelectric surface 2s has a first portion 11 having an electron incident surface 11s including a plurality of channels ch arranged while being separated from each other. In the photodetector 1, the distance b between the photoelectric surface 2s and the electron incident surface 11s, the interval Δch between the channels ch in the arrangement direction (second direction) of the channels ch, and the voltage V applied between the photoelectric surface 2s and the electron incident surface 11s satisfy the above formula (1). Thereby, the interval Δch between the channels ch is appropriately set according to the spread of the electron trajectories according to the voltage V between the photoelectric surface 2s and the electron incident surface 11s and the distance b from the photoelectric surface 2s to the electron incident surface 11s, so that the crosstalk between the channels ch is suppressed. In particular, in the photodetector 1, since the incident panel 2 is flat, it is easy to manufacture and it is easy to set the distance b between the photoelectric surface 2s and the electron incident surface 11s so as to satisfy each formula. Further, when the incident panel 2 is not flat, for example, by protruding the formation region of the photoelectric surface 2s toward the semiconductor element 10 (for example, making only the formation region of the photoelectric surface 2s thick and convex), it is also conceivable to adjust the distance b. In that case, as the incident panel 2 becomes thicker, the possibility that the incident light itself undergoes crosstalk within the incident panel 2 increases. Therefore, the incident panel 2 is preferably flat and has a thickness that can maintain mechanical strength (for example, 1 mm or more).

[0039] In addition, in the photodetector 1, the semiconductor element 10 is provided on both end sides of at least the electron incident surface 11s in the arrangement direction of the channel ch, and has a second portion 12 formed thicker than the first portion 11 by protruding toward the photocathode surface 2s side from the electron incident surface 11s. In the photodetector 1, the distance e from the end of the electron incident surface 11s to the end of the second portion 12 and the distance w from the end of the outermost channel ch to the start of the second portion 12 satisfy the above formula (2) or the above formula (3). Thereby, even if distortion occurs from the electron incident surface 11s to the second portion 12 with respect to the equipotential surface Sv between the photocathode surface 2s and the electron incident surface 11s, a decrease in the electron collection efficiency in the outermost channel ch is suppressed. As described above, according to the photodetector 1, it is possible to suppress crosstalk between the channels ch and a decrease in the electron collection efficiency.

[0040] In addition, the photodetector 1 can satisfy the above formulas (4) to (6). In this case, it is possible to reliably suppress crosstalk between the channels.

[0041] In addition, the photodetector 1 includes a side tube 3 whose one end is sealed by the incident surface plate 2, a stem 4 that seals the other end of the side tube 3, and an insulating base member 5 provided on the stem 4. The semiconductor element 10 is provided on the base member 5 such that the electron incident surface 11s faces the photocathode surface 2s side. Therefore, by setting the dimensions of each part of the side tube 3, the incident surface plate 2, and the base member 5, it is possible to realize a distance b that satisfies, for example, the above formula.

[0042] Furthermore, the photodetector 1 includes an insulating film 7 provided on at least the surface of the semiconductor element 10 facing the photocathode surface 2s and having a thickness of 100 nm or less. Therefore, at least by the insulating film 7 formed on the surface of the semiconductor element 10, the return of the gas ionized by the incident of photoelectrons onto the semiconductor element 10 to the photocathode surface 2s (ion feedback) is suppressed.

[0043] The above embodiments describe one aspect of the photodetector according to the present invention. Therefore, the photodetector according to the present invention is not limited to the above embodiments and can be arbitrarily modified.

[0044] For example, the photodetector 1 may not have the insulating film 7. Further, when only focusing on the aspect of suppressing crosstalk between the channels ch, the above formulas (2) and (3) do not have to be satisfied. In this case, the semiconductor element 10 may not have the second portion 12. That is, in the present embodiment, the semiconductor element 10 is a back-illuminated semiconductor element, but a front-illuminated semiconductor element may also be used.

[0045] Further, in the present embodiment, the photoelectric surface 2s is exemplified as including a photoelectric conversion layer made of a thin film of a compound semiconductor, but the photoelectric surface 2s may include a photoelectric conversion layer containing an alkali metal. Further, in the present embodiment, the base member 5 is exemplified as being formed in a rectangular parallelepiped block shape that protrudes convexly from the stem 4 toward the photoelectric surface 2s by an insulating material such as ceramic, but the base member 5 may be a plate-like member formed of an insulating material such as ceramic. In this case, a fixing portion for fixing the base member 5 at a desired position may be provided on the stem 4.

Description of Reference Numerals

[0046] 1... photodetector, 2... incident panel, 3... side tube, 4... stem, 5... base member, 7... insulating film, 10... semiconductor element, 11... first portion, 11s... electron incident surface, 12... second portion, b, e, w... distance, ch... channel, V... voltage.

Claims

1. an incident face plate having a photocathode that emits photoelectrons in response to incident light; a side tube having one end sealed by the entrance faceplate; an insulating base member provided so as to protrude toward the photocathode; a semiconductor element having an electron incident surface and provided on the base member such that the electron incident surface faces the photocathode along a first direction, the semiconductor element detecting the photoelectrons emitted from the photocathode; an insulating film provided on at least a surface of the semiconductor element facing the photocathode; Equipped with The insulating film is formed of a metal oxide. Photodetector.

2. An incident faceplate having a photocathode that emits photoelectrons in response to incident light; a side tube having one end sealed by the entrance faceplate; an insulating base member provided so as to protrude toward the photocathode; a semiconductor element having an electron incident surface and provided on the base member such that the electron incident surface faces the photocathode along a first direction, the semiconductor element detecting the photoelectrons emitted from the photocathode; an insulating film provided on at least a surface of the semiconductor element facing the photocathode; Equipped with The insulating film is formed on a surface of the base member. Photodetector.

3. The insulating film is formed of a metal oxide.

3. The photodetector of claim 2.

4. The metal oxide includes aluminum oxide.

4. The photodetector according to claim 1 or 3.

5. The thickness of the insulating film is 100 nm or less. The photodetector according to any one of claims 1 to 3.

6. The thickness of the insulating film is 30 nm or less.

6. The photodetector of claim 5.

7. a pin that penetrates the base member so as to protrude outside the side tube and that outputs an electrical signal detected by the semiconductor element to the outside; the insulating film is formed on a surface of the pin; The photodetector according to any one of claims 1 to 3.

8. a stem that seals the other end of the side tube and on which the base member is provided; the insulating film is formed on a unit including the semiconductor element, the base member, the stem, and the pin; 8. The photodetector of claim 7.

9. The base member is made of ceramic. The photodetector according to any one of claims 1 to 3.

10. The base member is located within the side tube. The photodetector according to any one of claims 1 to 3.

11. the semiconductor element has a first portion having the electron incident surface, the first portion being a surface facing the photocathode and including a plurality of channels arranged at a distance from each other along a second direction intersecting the first direction; The photodetector according to any one of claims 1 to 3.

12. the semiconductor element has a second portion provided on at least both ends of the electron incident surface in the second direction, protruding further toward the photocathode than the electron incident surface and formed to be thicker than the first portion; a distance b between the photocathode and the electron incident surface in the first direction and a distance e from an end of the electron incident surface to an end of the second portion on one side in the second direction satisfying distance b>distance e.

12. The optical detector of claim 11.

13. The semiconductor element is a back-illuminated semiconductor element. The photodetector according to any one of claims 1 to 3.

14. The entrance plate is formed in a flat plate shape. The photodetector according to any one of claims 1 to 3.

Images