JP3524249B2 - Electron tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron tube using a transmission type photocathode.

[0002]

2. Description of the Related Art As an example of an electron tube, there is a photomultiplier tube shown in FIG. In this photomultiplier tube, a glass face plate 10 is supported on one end of a vacuum tube 11, and light to be detected (hν) that is a detection target is incident as shown by an arrow.
Inside the vacuum tube 11, from the glass face plate 10 side, a transmission type photocathode 30 supported by a semiconductor substrate 60, a focusing electrode 70 for focusing photoelectrons (e ⁻ ), a dynode section 71 for multiplying photoelectrons by secondary electrons, and The anode 40 is sequentially arranged. Then, on the surface of the transmissive photocathode 30, a first electrode 50, which is capable of transmitting photoelectrons in a mesh shape or the like, is connected and formed, and a second electrode 51 is ohmic-connected to the rear surface side peripheral portion of the semiconductor substrate 60. Is formed. Further, one end of a stem pin 54a penetrating the end face of the vacuum tube 11 near the anode 40 is electrically connected to the first electrode 50 via the electric lead 53a, and similarly, one end of another stem pin 54b is the electric lead 53b. And vacuum tube 1
Second electrode 5 via metal wiring 52 extending from one side wall
It is connected to 1. Each stem pin 54a, the other end of the b is connected to a bias voltage V _B, and to be able to apply a bias voltage V _B to the transmission type photocathode 30. In FIG. 13, the anode 40, the focusing electrode 70, and the dynode portion 7
The electrical leads and the like connected to 1 are omitted.

FIG. 14 is an enlarged sectional view of the transmission type photocathode 30 shown in FIG. The transmissive photocathode 30 includes a light absorption layer 32 that absorbs light to be detected and generates photoelectrons, and a light absorption layer 3
An electron emission layer 31 for drifting photoelectrons from No. 2 to the surface of the transmission type photocathode 30 is sequentially stacked on the surface of the semiconductor substrate 60, and the first electrode 50 capable of transmitting photoelectrons is formed on the surface of the electron emission layer 31 by the Schottky. It is formed by joining.
In addition, the second electrode 51 is provided on the peripheral portion on the back surface side of the semiconductor substrate 60.
Are formed in ohmic contact.

When a reverse bias voltage V _B is applied to the transmissive photocathode 30 via the first electrode 50 and the second electrode 51, a depletion layer at the interface between the electron emission layer 31 and the first electrode 50. Expands. Since an electric field is formed from the first electrode 50 toward the electron emission layer 31 in the depletion layer, the light absorption layer 3
When the photoelectrons from 2 reach the electron emission layer 31 by diffusion, the photoelectrons are accelerated by the electric field and the first electrode 50
Diffuses and drifts toward and is easily released into a vacuum. The photoelectrons due to the incident light to be incident on the transmissive photocathode 30 are accelerated by the electric field of the depletion layer inside the transmissive photocathode 30, transition to a higher energy band, and then are emitted into a vacuum. Type photocathode, which is referred to as US Pat. No. 3958143 or JSEscher and
R. Sakaran Appl. Phys. Lett., 29, 2, 87 (1976).

[0005]

However, in the conventional transmission type photocathode, since the second electrode 51 is formed on the peripheral portion on the back surface side of the semiconductor substrate 60, incident light to be detected is small in this portion. It hinders it. Further, as shown in FIG. 13, since the transmission type photocathode 30 supported by the semiconductor substrate 60 is supported in the vacuum tube 11 by the metal wiring 52, a gap is generated between the glass face plate 10 and the semiconductor substrate 60. Here, multiple reflection occurs and the light intensity is attenuated. Further, since the semiconductor substrate 60 is relatively thick in order to maintain the mechanical strength of the transmissive photoelectric surface 30, the light intensity reaching the light absorption layer 32 is attenuated by the semiconductor substrate 60 itself.

Although the above-described light attenuation does not pose a serious problem in a normal photodetector or an image pickup device, extremely weak light such as a photomultiplier tube or a light intensifier tube (image intensifier) is not detected. This is a very important problem in a detection device. In particular, in a photon counting type apparatus for observing the detected light at a photon level, when the detected light is attenuated, the detection time becomes long, and a moving object (for example, a biological sample) cannot be observed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electron tube capable of detecting the detected light while suppressing the attenuation thereof.

[0008]

The electron tube according to the present invention comprises:
The glass face plate on which the light to be detected, which is the detection target, is incident, the vacuum tube whose inside is maintained in a vacuum state by supporting the glass face plate at the end of the side wall, and the glass face plate are provided so as to be in close contact with the inside surface of the glass face plate. An antireflection film that prevents reflection of light, a transmissive photocathode that is disposed on the antireflection film and that emits photoelectrons to the internal space of the vacuum tube by receiving the light to be detected, and a transmissive photocathode that is installed inside the vacuum tube. An electron tube having an anode for holding a positive voltage with respect to, a transmission type photocathode being a window formed of a p-type compound semiconductor on an antireflection film and blocking light having a wavelength shorter than that of the light to be detected. Layer, a p-type compound semiconductor having a bandgap energy smaller than that of the window layer, formed into a mesa shape on the window layer, and absorbing light to be detected to generate photoelectrons; Formed on the absorbent layer An electron emission layer to the drift photoelectrons from the light-absorbing layer, which is formed by connecting the metal or alloy in the electron emission layer, a first electrode photoelectrons can transmit,
And a second electrode formed by being connected to the upper surface of the peripheral portion of the window layer by a metal or an alloy. As a result, when the light to be detected enters the transmissive photocathode, there is no obstruction, and there is no gap between the glass face plate and the transmissive photocathode, and the attenuation of the light to be detected can be suppressed.

Further, the first electrode is characterized in that the metal or alloy is formed in a pattern shape by being substantially uniformly distributed on the electron emission layer, and the electron emission layer is exposed substantially uniformly. As a result, photoelectrons from the electron emission layer are uniformly emitted into the vacuum tube internal space.

Further, n is provided between the electron emission layer and the second electrode.
It is characterized in that a contact layer made of a type compound semiconductor is interposed. As a result, a depletion layer is formed by the pn junction between the electron emission layer and the contact layer, and an electric field is formed from the contact layer to the electron emission layer in the depletion layer.

The light absorption layer is made of In _x Ga _1-x As _y P _1-y (0 <x <1,0 <y <1) lattice-matched with the window layer and the electron emission layer, and the window layer is It is made of a compound semiconductor or a mixed crystal thereof having a bandgap energy larger than that of the light absorption layer. The lattice matching increases the diffusion length of photoelectrons, and the band gap energy can be arbitrarily changed by arbitrarily changing the atomic composition ratio of the light absorption layer.

Further, the light absorption layer is formed of a quantum well structure of at least two kinds of semiconductor multilayer films, and absorbs the detected light between subbands formed in the conduction band of the quantum well structure to generate photoelectrons. It is characterized by With this, the gap energy between the sub-bands can be arbitrarily changed by arbitrarily changing the type and thickness of the semiconductor multilayer film.

Further, the transmission type photocathode is characterized by being a transition electron type. As a result, photoelectrons can be accelerated by the electric field of the depletion layer inside the transmissive photocathode, transition to a higher energy band, and then emitted into a vacuum.

Further, a multiplication means for multiplying secondary electrons of photoelectrons emitted from the transmission type photocathode is provided between the transmission type photocathode and the anode. This allows the emitted photoelectron signal to be multiplied.

Further, between the transmission type photocathode and the anode, a multiplying means for multiplying secondary electron of a two-dimensional photoelectron image emitted from the transmission type photocathode corresponding to the two-dimensional optical image of the detected light. Is provided, and the anode is a fluorescent film that emits light by receiving a two-dimensional electron image that has been subjected to secondary electron multiplication by the multiplication means. This makes it possible to observe a two-dimensional optical image obtained by enhancing the two-dimensional optical image of the detected light.

Finally, the anode receives a two-dimensional electronic image corresponding to the two-dimensional optical image of the light to be detected incident on the transmission type photocathode and outputs an electric signal corresponding to the two-dimensional optical image. Is characterized in that. Thereby, the two-dimensional optical image can be converted into an electric signal.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described for each embodiment with reference to the drawings.

First Embodiment of Electron Tube FIG. 1 is a side sectional view of a so-called line-focus type photomultiplier tube. In FIG. 1, a glass face plate 10 is supported on one end of a cylindrical body that constitutes the main body of a vacuum tube 11, and light to be detected (hν) to be detected is incident as shown by an arrow. The other end of the tubular body forming the vacuum tube 11 is also hermetically sealed with glass to keep the inside of the vacuum tube 11 in a vacuum state. As will be described later with reference to FIG. 2, the antireflection film 2 is formed on the inner surface of the glass face plate 10.
0 is provided so as to be in close contact, and a transmissive photocathode 30 made of a semiconductor and having a mesa cross section is disposed on the antireflection film 20. Is formed by connecting the second electrode 51.

An anode 40 is installed at the other end of the vacuum tube 11, and photoelectrons (e ⁻ ) are converged between the transmission photocathode 30 and the anode 40 toward the transmission photocathode 30. The converging electrode 70 is installed, and the dynode section 71 (multiplication means) composed of a plurality of stages of dynodes 71a to 71h for sequentially multiplying the photoelectrons emitted from the transmission type photocathode 30 is curved near the anode 40. The electrodes are arranged in multiple stages. One end of a stem pin 54a penetrating the end surface of the vacuum tube 30 near the anode 40 is connected to the first electrode 50 via an electric lead 53a in the vacuum tube 11,
Further, one end of another stem pin 54b penetrates the end face of the vacuum tube 11 near the anode 40 and is connected to one end of the electric lead 53b, and the other end of the electric lead 53b is connected to the second electrode through the metal wiring 52 on the inner wall of the vacuum tube 11. It is connected to 51.
Each stem pin 54a, the other end of the b is connected to a bias voltage V _B, it is to be applied to the transmission type photocathode 30 a bias voltage V _B through a respective stem pins 54a, b. Although not shown in FIG. 1, the transmissive photoelectric surface 30,
For the focusing electrode 70, the dynode portion 71, and the anode 40,
Through the bleeder circuit and electrical leads, the transmission type photocathode 3
A positive bleeder voltage with respect to 0 is distributed and applied so as to increase step by step as it approaches the anode 40.

Next, the main part of this embodiment, that is, the installation state of the transmission type photocathode 30 on the glass face plate 10 will be described in detail with reference to FIG.

As shown by the arrow in FIG. 2, the detected light (h
ν) is incident from the lower surface side of the glass face plate 10. On the glass face plate 10, SiO ₂ and Si are formed with a film thickness according to the wavelength of the light to be detected.
_An antireflection film 20 in which ₃ N ₄ and ₃ N ₄ are sequentially laminated is provided so as to be in close contact with each other to prevent reflection of light to be detected. A window layer 33 made of p ⁺ type InAlGaAs is formed on the antireflection film 20 so as to be in close contact therewith, and blocks light having a wavelength shorter than that of the light to be detected. In this way, since the glass face plate 10 and the window layer 33 are in close contact with each other via the antireflection film 20, the light to be detected is not multiple-reflected and its intensity is not attenuated efficiently, and the transmission type photoelectric surface 30 is efficiently used. Is incident on the window layer 33 constituting the.

On the window layer 33, a light absorption layer 32 made of p--type InGaAs having a bandgap energy smaller than that of the window layer 33 is deposited in a narrower area than the window layer 33, and its cross-sectional shape is formed into a mesa shape. Has been done. Therefore, the upper surface of the peripheral portion of the window layer 33 is exposed, and thus the second electrode made of AuZn is attached to the glass face plate 10 and the window layer 33 with the antireflection film 20 interposed therebetween. The ohmic contact 51 can be formed easily and with good yield. Further, since the second electrode 51 does not interfere with the detected light traveling toward the light absorption layer 32, it is possible to efficiently absorb the detected light and generate photoelectrons.
The number of photoelectrons generated in the light absorption layer 32 forming the transmissive photocathode 30 is larger than that in the conventional case.

An electron emission layer 31 made of p-type InP is formed on the light absorption layer 32, and a first electrode 50 that is in Schottky contact with the electron emission layer 31 is provided on the electron emission layer 31. The first electrode 50 is connected to the electric lead 53a of FIG. 1 via a wire or the like (not shown), while the second electrode 5 described above is connected.
1 is connected to the electric lead 53b through the conductive pattern on the inner surface of the glass face plate 10 so that a bias is applied. Therefore, since an electric field is formed from the first electrode 50 toward the electron emission layer 31 in the depletion layer formed at the Schottky junction interface by applying this bias, photoelectrons from the light absorption layer 32 are generated. It can be diffused and drifted toward the first electrode 50 side through the electron emission layer 31. In addition, the first electrode 50 is formed in a very uniform and extremely thin distribution, so that the first electrode 50 is formed in an island-shaped pattern, and therefore the electron emission layer 3 is formed.
1 is exposed substantially uniformly, which allows the photoelectrons from the electron emission layer 31 to be uniformly emitted to the outside.

The photomultiplier tube of FIG. 1 having the features shown in FIG. 2 operates as follows.

Of the light that has entered the glass face plate 10 and has reached the window layer 33 with almost no attenuation, light of a shorter wavelength than the light to be detected is blocked, and only the light to be detected that has passed through the window layer 33 is blocked. The light absorbing layer 3 without being blocked by the second electrode 51.
Reach 2. Of the detected light that has reached the light absorption layer 32, the detected light having a bandgap energy of the light absorption layer 32 or more is absorbed, so that photoelectrons are generated. Further, since the reverse bias voltage V _B is applied to the transmissive photoelectric surface 30 via the first electrode 50 and the second electrode 51, photoelectrons diffuse and drift toward the first electrode 50 side, and
It is easily discharged into the internal space of the vacuum tube 11 through the gap of the pattern of the electrode.

The photoelectrons (e ⁻ ) emitted into the vacuum are converged by the converging electrode 70 and accelerated and incident on the first dynode 71a. Secondary electrons, which are several times as many as the number of incident photoelectrons, are emitted and are accelerated and incident on the second dynode 71b. In the second dynode 71b as well as in the first dynode 71a, 2
Secondary electrons are emitted. By repeating this eight times, the photoelectrons emitted from the transmission type photocathode 30 are finally multiplied by about 1,000,000 times and emitted in the eighth dynode 71h. And the eighth dynode 71
The multiplied secondary electrons emitted from h are collected by the anode 40 and taken out as an output signal current.

As described above, since the number of photoelectrons emitted from the transmission type photocathode 30 is large, the signal current finally outputted from the anode 40 is also large, which is larger than that of the conventional line focus type photomultiplier tube. Therefore, weaker light to be detected can be detected.

The transmission type photocathode 30 constituting the above photomultiplier tube will be described by a manufacturing method. 3 (a) to (i)
2A to 2C are sectional views taken along the line AA of FIG.

First, a semiconductor substrate 60 made of n-type InP is prepared. Next, using an epitaxial growth apparatus (not shown), a 1 μm thick etch stop layer 61 made of p − type InGaAs and a 1 μm thick electron emission layer 31 made of p − type InP on the n type InP semiconductor substrate 60. , A p-type InGaAs light absorbing layer 32 having a thickness of 2 μm, and p ⁺ -type InAlGaAs
A window layer 33 having a thickness of 4 μm is sequentially epitaxially grown to form a semiconductor multilayer film as shown in FIG. At this time, the etch stop layer 61 and the electron emission layer 3
1 and the carrier concentration of the light absorption layer 32 is 1 to 10 × 10 ¹⁶ cm
^-3 is desirable, and the carrier concentration of the window layer 33 is 1
It is desirable that the value is × 10 ¹⁸ cm ^-3 or more, but it is not necessarily limited to these values. Further, the thicknesses of the etch stop layer 61, the electron emission layer 31, the light absorption layer 32, and the window layer 33 are not limited to the above thicknesses.

Then, as shown in FIG. 3B, the window layer 3
On top of Si ₃ N ₄ , Si with a film thickness according to the wavelength of the detected light.
The antireflection film 20 is formed by depositing O ₂ in this order using the CVD method.

Next, the glass face plate 10 is heated to about 550 ° C. in vacuum or in an inert gas, thermocompression-bonded to the semiconductor multilayer film on the surface where the antireflection film 20 is formed, and the glass face plate 10 is cooled to room temperature. As shown in FIG. 3C, the antireflection film 20 is in close contact with the glass face plate 10 to suppress multiple reflection of the detected light. In this state,
As shown in (d), when the semiconductor substrate 60 is removed by etching using an HCl solution, the etching stop layer 61 automatically stops and the lower surface of the etch stop layer 61 is exposed.

Next, the etch stop layer 61 whose bottom surface is exposed is removed by etching using H ₂ SO ₄ , H ₂ O ₂ and H ₂ O solutions, and the electron emission layer 31 is automatically stopped.
As shown in (e), the lower surface of the electron emission layer 31 is exposed.

Next, a photoresist 80 is applied to the electron emission layer 31, and photolithography is performed using a predetermined mask to expose the lower surface peripheral portion of the electron emission layer 31 as shown in FIG. 3 (f). Form a pattern.

In this state, when the peripheral portions of the electron emission layer 31 and the light absorption layer 32 are removed by etching with aqua regia, the lower peripheral portion of the window layer 33 is exposed as shown in FIG. 3 (g). The electron emission layer 31 and the light absorption layer 32 have a mesa shape with respect to the window layer 33. After that, as shown in FIG. 3H, the photoresist 80 applied to the lower surface of the electron emission layer 31 is removed.

Next, the mesa-shaped portion is masked with a mechanical mask. Then, a second electrode 51 made of AuZn alloy having a thickness of 500 nm is vapor-deposited and formed on the exposed lower surface of the glass face plate 10, the antireflection film 20, and the window layer 33 by using a vapor deposition device (not shown). It often makes ohmic contact with the window layer 33. Finally, the first electrode 50 made of Al and having a thickness of 500 nm is formed on the electron emission layer 31 by using a predetermined mask.
It is vapor-deposited on the upper surface while being uniformly distributed in an island shape, and is in Schottky contact with the electron emission layer 31. Here, when the mechanical mask is removed, as shown in FIG. 3I, the electron emission layer 31 is exposed substantially uniformly, and the transmission type photocathode 30 having a pattern shape capable of transmitting photoelectrons is formed. Is
It is incorporated into the photomultiplier tube shown in FIG.

Second Embodiment of Electron Tube FIG. 4 is a side sectional view of a so-called proximity type photomultiplier tube. As described in the first embodiment of the electron tube, the transmission type photocathode 30 is provided in close contact with the inner surface of the glass face plate 10 through the antireflection film 20, and the glass face plate similar to that of FIG. 10 is a vacuum tube 1 using a sealing member composed of an In seal portion 13 and an In reservoir 14.
The light to be detected (hν), which is supported by the upper end of the cylindrical body that constitutes the main body of No. 1, is incident as indicated by the arrow.

The bottom plate 12 is supported at the lower end of the cylinder forming the main body of the vacuum tube 11, and the vacuum tube 11 is hermetically sealed to keep the inside of the vacuum tube 11 in a vacuum state. On the upper surface of the bottom plate portion 12, facing the transmissive photoelectric surface 30,
A photodiode 41 is provided which has a multiplication effect when photoelectrons are driven in. One end of the stem pin 54 connected to the photodiode 41 has a bottom plate portion 12
A reverse bias voltage is applied to the photodiode 41 via the same, and also a stem pin 54 and an electrical lead (not shown) connected to the transmissive photocathode. A voltage of + several kV is applied between the transmissive photocathode 30 and the photodiode 41 via the. The electrical leads and the like connected to the first electrode 50 and the second electrode 51 are not shown.

When the light to be detected enters the photomultiplier tube, the light to be detected efficiently enters the transmission type photocathode 30 as described in the first embodiment of the electron tube.
^- ) Is released. Then, the emitted photoelectrons are accelerated and driven into the photodiode 41,
Secondary electrons multiplied by several thousand times are generated for one photoelectron. Then, the secondary electrons generated in the photodiode 41 are taken out as an output signal via the stem pin 54.

Therefore, a large number of photoelectrons are emitted from the transmission type photocathode, so that a weaker signal can be detected as compared with the conventional electron implantation type photomultiplier tube. Also,
Since it does not require a dynode section and does not require a focusing electrode as compared with the electrostatic focusing photomultiplier tube described later,
Can be miniaturized.

Third Embodiment of Electron Tube FIG. 5 is a side sectional view of a so-called electrostatic focusing photomultiplier tube. This photomultiplier tube is different from the second embodiment in that the transmission type photocathode 30 and the photodiode 41 are different.
That is, a pair of focusing electrodes 70 is installed between and. Then, one end of each electric lead 53a, b connected to the pair of focusing electrodes 70 extends through the side wall of the vacuum tube 30, and a predetermined voltage can be applied to the focusing electrode 70 via these electrical leads 53a, b. I am trying.

According to the present embodiment, since the photoelectrons are converged by the converging electrode 70, the photodiode 41 smaller than the effective area of the transmission type photocathode can be used.
Moreover, since the photodiode 41 can be downsized, high-speed response is possible.

Fourth Embodiment of Electron Tube FIG. 6 is a side sectional view of an image intensifying tube. The present embodiment is different from the second to third embodiments in that the vacuum tube 1
A microchannel plate (hereinafter referred to as "MCP") (hereinafter referred to as "MCP") formed by bundling a large number of glass holes with a diameter of about 10 μm so that two-dimensional electrons can be multiplied by secondary electrons Double means) 72 is installed. Then, the transmissive photocathode 30 and the MCP 72
A voltage of + several 100V is applied between the transmissive photocathode 30 and the MCP 72 via each electric lead (not shown) connected to. Further, one end of each of the electric leads 53a and 53b connected to the MCP 72 extends through the side wall of the vacuum tube 11, and the upper surface side of the MCP 72 (hereinafter referred to as "input side") and the lower surface side of the MCP 72 (hereinafter referred to as "input side") are passed through them. A voltage for multiplication is applied between the “output side” and the “output side”.

Further, in the present embodiment, unlike the above-described embodiment, the fiber plate 42 is supported at the lower end of the cylindrical body constituting the main body of the vacuum tube 11, and the phosphor 43 (fluorescent film) is provided on the inner surface thereof. Are arranged. Then, through the electric lead 53c connected to the phosphor 43 and another electric lead (not shown) connected to the MCP 72, M
A voltage of about several kV with respect to CP 72 is applied to the phosphor 43. The first electrode 50 and the second
The electrical lead connected to the electrode 51 is omitted in the figure.

Therefore, the detected light is incident on the image intensifying tube as shown in FIG.
In this way, the two-dimensional photoelectron image (e ⁻ ) corresponding to the two-dimensional optical image is emitted from the transmission type photocathode 30 into the internal space of the vacuum tube 11, and is accelerated and incident on the input side of the MCP 72. The MCP 72 double-multiplies the two-dimensional photoelectron image by about one million times, and a two-dimensional electron image corresponding to the incident position is emitted from the output side of the MCP 72 and accelerated and enters the phosphor 43. On the phosphor 43, a two-dimensional image corresponding to the two-dimensional electron image is intensified and emitted for display. Two-dimensional image shows fiber plate 42 supporting phosphor 43
It is taken out through and observed.

In this embodiment, since the transmission type photocathode 30 described in the photomultiplier tube is used, the light to be detected can be taken in more efficiently than in the conventional case. More three-dimensional photoelectrons are emitted than before. Therefore, the light emitted from the phosphor 43 due to the multiplied two-dimensional electrons becomes stronger than before, so that a weaker two-dimensional optical image can be observed as compared with the conventional image intensifying tube, that is, the limit resolution is reduced. Improved high quality 2
Dimensional image characteristics can be obtained.

Fifth Embodiment of Electron Tube FIG. 7 is a side sectional view of a so-called proximity type image pickup tube. In this image pickup tube, instead of the photodiode 41 in the second embodiment, a charge storage element (hereinafter referred to as “CCD”) 44 which is an image pickup device is used. A voltage for multiplying the emitted photoelectrons is applied between the transmissive photocathode 30 and the CCD 44, and the accelerated photoelectrons enter the CCD 44 to multiply the photoelectron image. The charges accumulated in each pixel of the CCD 44 are output to the outside in time series via the stem pin 54.

Also in the present embodiment, more two-dimensional photoelectrons are emitted from the transmissive photocathode than in the conventional case.
The number of multiplication electrons stored in each pixel of the CCD 44 is also larger than in the conventional case. Therefore, it becomes possible to electrically detect a two-dimensional optical image that is weaker than in the past, and high-quality two-dimensional image characteristics with improved critical resolution can be obtained.

The first to third electron tubes of the present invention are used.
In the embodiment, the case where the dynode or the photodiode is used as the multiplication means has been described, but the multiplication means is not necessarily limited to the above, and other multiplication means such as MCP may be used. Further, although the proximity type image pickup tube has been described in the fifth embodiment of the electron tube, an electrostatic focusing type image pickup tube in which a focusing electrode is provided between the transmission type photocathode and the CCD may be used. Further, although the case where the CCD is used as the image pickup device in the fifth embodiment of the electron tube has been described, the present invention is not limited to this, and a solid-state detector having a position detection function, for example, a position detection photodiode or the like may be used. Of course not. Finally, in the present invention, the photomultiplier tube, the image intensifying tube, and the image pickup tube have been described as the electron tube, but it goes without saying that they can be applied to other photodetection devices such as a streak tube including these.

In the first to fifth embodiments of the electron tube according to the present invention, the transmissive photocathode has been described using the one shown in FIG. 2, but the transmissive photocathode is not necessarily limited to the above. Absent. Therefore, in the following, modifications of the transmission type photocathode included in the electron tube according to the present invention will be described.

First Modified Example of Transmissive Photocathode The first modified example of the transmissive photocathode is different from the above transmissive photocathode in that the Schottky junction is formed on the electron emission layer 31 as shown in FIG. That is, the first electrode 50 made of Al is formed in a substantially uniform mesh distribution, and has a pattern shape in which the electron emission layer 31 is exposed substantially uniformly. In the first modification, as shown in FIG. 8, since the first electrode 50 can be easily connected to the electric lead 53a at the end, photoelectrons are uniformly emitted to the outside from the transmissive photoelectric surface. It will be easy.

Next, a first modified example of the transmission type photocathode will be described by a manufacturing method. 9 (i) to 9 (n) are sectional views taken along the line AA of FIG. 8 in the order of steps. The steps similar to those of the transmission type photocathode described in the first embodiment of the electron tube are shown. Omitted. That is, as shown in FIG.
Illustration and description are omitted up to the step of removing the photoresist 80 applied to the electron emission layer 31 of the epitaxial multilayer film after etching the window layer 33 and the light absorption layer 32 into a mesa shape.

After the steps up to FIG. 3H, as shown in FIG. 9I, the first electrode 5 made of Al is formed on the lower surface of the electron emission layer 31.
0 is vapor-deposited to a thickness of about 20 μm to form a Schottky junction with the electron emission layer 31.

Next, a photoresist 80 is applied to the lower surface of the first electrode 50, and photolithography is performed using a predetermined mask. As shown in FIG. 9J, the first electrode 50 has a mesh-shaped mask. A pattern is formed. Next, in this state, the first electrode 50 is removed by etching using a H ₂ SO ₄ solution (see FIG. 9K), and the photoresist 80 applied to the lower surface of the first electrode 50 is removed (see FIG. 9). (1)), the pattern mesh-shaped first electrode 50 is formed so that the electron emission layer 31 is uniformly exposed.

Thereafter, the second electrode 51 made of AuZn alloy is used.
By performing the step of vapor-depositing on the peripheral portion of the lower surface of the window layer 33, as shown in FIG. 9 (m), a transmission type photocathode that can be incorporated into the electron tube described in each of the above-described embodiments is obtained.

Second Modified Example of Transmissive Photocathode A second modified example of the transmissive photocathode is different from the first modified example in that
As shown in FIG. 10, a contact layer 34 made of n ⁺ -type InP is formed in a mesh pattern on the electron emission layer 31 so as to form a pn junction with the contact layer 34. The contact layer 34 is made of AuGe in ohmic contact with the contact layer 34. The first electrode 50 is similarly formed in a mesh pattern, and as a result, the electron emission layer 31 is exposed substantially uniformly. Therefore, an electric field from the contact layer 34 to the electron emission layer 31 is generated in the depletion layer formed at the interface of the pn junction. Therefore, if a reverse bias voltage is applied to the transmissive photocathode 30 of the present modification via the first electrode 50 and the second electrode 51, the depletion layer is used as described in the first embodiment of the electron tube. The photoelectrons from the light absorption layer 32 are easily diffused and drifted toward the electron emission layer 31 side, and can easily jump out of the transmission type photocathode 30.

Next, a second modification of the transmissive photocathode will be described with a manufacturing method. 11 (a) to (g) and FIG.
2 (h) to (m) are sectional views taken along the line AA of FIG.

In this modification, the semiconductor multilayer film forming process is different from that of the first embodiment shown in FIG.
As shown in (a), the n-type InGaAs etch stop layer 61
A contact layer 34 made of n ⁺ -type InP and having a thickness of 0.5 μm
N ⁺ InP contact layer 3 after epitaxial growth
The p-type InP electron emission layer 31 is epitaxially grown on the surface of the semiconductor layer 4 so that both of them form a pn junction. At this time, the carrier concentration of the contact layer 34 is preferably 1 × 10 ¹⁸ cm ⁻³ or more, but is not necessarily limited to these values, and the thickness thereof is not limited to the above.

Next, as described in the first embodiment, the antireflection film 20 is formed (see FIG. 11B), and the semiconductor multilayer film and the glass face plate 10 are thermocompression bonded on the surface where the antireflection film is formed. , (See FIG. 11C), the semiconductor substrate 60 and the etch stop layer 61 are subsequently removed by etching (FIG. 1).
1 (d) and (e)), the lower surface of the contact layer 34 is exposed.

Then, by photolithography, a mask pattern in which the lower peripheral portion of the contact layer 34 is exposed is formed using the photoresist 80 (see FIG. 11F), and in this state, the contact layer is formed using aqua regia. When the peripheral portions of 34, the electron emitting layer 31, and the light absorbing layer 32 are removed by etching, the lower peripheral portion of the window layer 33 is exposed, and the electron emitting layer 3
1 and the light absorption layer 32, the contact layer 34 is a window layer 33.
On the other hand, it has a mesa shape (see FIG. 11 (g)). After that, the photoresist 80 on the lower surface of the contact layer 34 is removed (see FIG. 11 (h)).

Next, the first electrode 50 made of AuGe is vapor-deposited on the lower surface of the contact layer 34 to a thickness of about 80 μm to bring the contact layer 34 and the first electrode 50 into ohmic contact (FIG. 1).
2 (i)).

Next, in the step of forming the mesh-shaped mask pattern described in the first modified example, the mesh-shaped mask pattern is formed using the photoresist 80 (see FIG. 12 (j)). In this modification, the first electrode 50 and the contact layer 34 are removed by etching with an HCl solution (see FIG. 12 (k)), and the photoresist 80 is removed (see FIG. 12 (l)). A pattern in which the contact layer 34 has a mesh shape is formed, and the electron emission layer 31 is uniformly exposed.

After that, the second electrode 51 made of AuZn alloy is formed.
By performing the step of vapor-depositing on the peripheral portion of the lower surface of the window layer 33, as shown in FIG. 12 (m), a transmission type photocathode that can be incorporated into the electron tube described in each of the above-described embodiments is obtained.

Although the light absorption layer 32 made of p-type InGaAs is used in the above-mentioned embodiments of the transmission type photocathode and each modification, the present invention is not limited to this, and In _x Ga _1-x As. _y P
_The light absorption layer 32 made of _1-y (0 <x <1,0 <y <1) is a window layer made of a compound semiconductor having a band gap energy larger than that of the electron emission layer 31 and the light absorption layer 32 or a mixed crystal thereof. 33
It may be formed in lattice matching with. by this,
Since crystal defects are suppressed in the light absorption layer 32 and the diffusion length of photoelectrons is lengthened, an electron tube in which the sensitivity of the transmissive photoelectric surface 30 is improved can be provided. Then, if the atomic composition ratio is arbitrarily changed, the bandgap energy of the light absorption layer 32 can be arbitrarily changed, and the spectral sensitivity characteristic of the electron tube incorporating the transmission type photocathode 30 can be arbitrarily changed.

The light absorption layer 32 is formed of a quantum well structure of two or more kinds of semiconductor multilayer films, and absorbs light between subbands formed in the conduction band of the quantum well structure to generate photoelectrons. Good. As a result, the gap energy between the sub-bands can be arbitrarily changed in the semiconductor multilayer film of which type and thickness are arbitrarily changed, so that it is possible to provide the electron tube in which the spectral sensitivity characteristic of the transmission type photocathode 30 can be arbitrarily changed.

Further, since an alkali metal oxide such as Cs ₂ O or an alkali metal is formed on the exposed surface of the electron emission layer 31, the work function of the exposed portion of the electron emission layer 31 is reduced and photoelectrons are more easily transferred to the outside. Since it can be emitted, an electron tube in which the sensitivity of the transmissive photocathode 30 is improved can be provided.

[0066]

According to the electron tube of the present invention, the transmission type photocathode is disposed on the glass face plate supported at the end of the vacuum tube so as to be in close contact with the antireflection film, and the light absorption layer and Electrodes are formed on the upper surface of the peripheral portion of the window layer in which the electron emission layer is formed in a mesa shape. Therefore, there is no multiple reflection between the glass face plate and the transmissive photoelectric surface, and there is nothing that interferes when the detected light enters the transmissive photoelectric surface, so that the attenuation of the detected light is suppressed. , It is possible to provide an electron tube which can detect weaker light as compared with a conventional electron tube, and in particular,
It is possible to provide an electron tube with improved critical resolution when detecting a two-dimensional optical image.

The first electrode patterned by being evenly distributed on the electron emitting layer exposes the electron emitting layer almost uniformly, so that the photoelectrons from the transmission type photocathode are uniformly distributed inside the vacuum tube. It is possible to provide an electron tube that can be emitted into the air, and particularly an electron tube that can obtain high-quality two-dimensional image characteristics when detecting a two-dimensional optical image.

Further, by making the transmissive photocathode a transition electron type, photoelectrons can be easily emitted from the transmissive photocathode 30, so that the output signal finally output from the anode also becomes large, It is possible to provide an electron tube capable of detecting weaker light as compared with a conventional electron tube, and particularly to provide an electron tube having an improved limit resolution when detecting a two-dimensional optical image.

Further, by changing the composition of the light absorption layer to lattice-match with the window layer and the electron emission layer or to form a quantum well structure, an electron tube whose spectral sensitivity characteristic can be changed with arbitrarily high sensitivity can be obtained. Can be provided.

[Brief description of drawings]

FIG. 1 is a view showing a side cross section of a first embodiment of an electron tube according to the present invention.

FIG. 2 is a perspective view of a first embodiment of a transmission type photocathode provided in the electron tube according to the present invention, and a diagram showing a part thereof in a cross section.

FIG. 3 is a diagram showing a manufacturing process for the cross-sectional view taken along the line AA of FIG.

FIG. 4 is a view showing a side cross section of a second embodiment of an electron tube according to the present invention.

FIG. 5 is a view showing a side cross section of a third embodiment of the electron tube according to the present invention.

FIG. 6 is a view showing a side cross section of a fourth embodiment of an electron tube according to the present invention.

FIG. 7 is a diagram showing a side cross section of a fifth embodiment of an electron tube according to the present invention.

FIG. 8 is a perspective view of a first modified example of the transmission type photocathode included in the electron tube according to the present invention, in which a part thereof is shown in cross section.

FIG. 9 is a diagram showing a manufacturing process for the cross-sectional view taken along the line AA of FIG. 8.

FIG. 10 is a perspective view of a second modification of the transmission type photocathode provided in the electron tube according to the present invention, in which a part thereof is shown in cross section.

FIG. 11 is a diagram showing a manufacturing process for the cross-sectional view taken along the line AA of FIG. 10.

12 is a view showing the sequel to the manufacturing process of FIG. 11 with respect to the cross-sectional view taken along the line AA of FIG.

FIG. 13 is a view showing a side cross section of a conventional electron tube.

14 is an enlarged cross-sectional view of a transmission type photocathode provided in the electron tube shown in FIG.

[Explanation of symbols]

10 ... Glass face plate, 11 ... Vacuum tube, 12 ...
Bottom plate part, 13 ... In seal part, 14 ... In reservoir, 2
0 ... Antireflection film, 30 ... Transmission type photocathode, 31.
..Electron emission layer, 32 ... Light absorbing layer, 33 ... Window layer, 34 ... Contact layer, 40 ... Anode, 41.
..Photodiodes, 42 ... Phosphors, 43 ...
Fiber plate, 44 ... Charge storage element, 50 ...
..First electrodes, 51 ... Second electrodes, 53 ... Metal wiring, 53, 53a, b, c ... Electrical leads, 54, 5
4a, b ... Stem pin, 60 ... Semiconductor substrate, 6
1 ... Etch stop layer, 70 ... Focusing electrode, 71
... Dynode section, 71a ... First dynode, 7
1b ... 2nd dynode, 71c ... 3rd dynode, 71d ... 4th dynode, 71e ... 5th dynode, 71f ... 6th dynode, 71g ...
7th dynode, 71h ... 8th dynode, 72 ...
..Micro channel plates

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H01J 43/08 H01J 43/08 (72) Inventor Hirofumi Suga 1126-1 Nonomachi, Hamamatsu-shi, Shizuoka Prefecture 1 Hamamatsu Photonics Co., Ltd. (56 ) Reference JP 7-73801 (JP, A) JP 7-161288 (JP, A) JP 2-234323 (JP, A) JP 7-262909 (JP, A) JP 5-234501 (JP, A) JP-A-6-243795 (JP, A) JP-A-62-133633 (JP, A) JP-A-9-503091 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 40/06 H01J 1 / 34,1 / 35 H01J 31/26 H01J 31/50 H01J 40/16 H01J 43/08

Claims (9)

(57) [Claims] 1. A glass face plate on which light to be detected, which is a detection target, is incident, a vacuum tube whose inside is maintained in a vacuum state by supporting the glass face plate at an end of a side wall, and a glass tube is closely attached to an inner surface of the glass face plate. An antireflection film that is provided so as to prevent reflection of the light to be detected, and a transmissive photoelectric surface that is disposed on the antireflection film and that emits photoelectrons to the internal space of the vacuum tube by receiving the light to be detected. An electron tube provided inside the vacuum tube, the anode holding a positive voltage with respect to the transmission type photocathode,
The transmissive photocathode is formed of a p-type compound semiconductor on the antireflection film, and has a window layer that blocks light having a shorter wavelength than the light to be detected, and a p-type compound having a bandgap energy smaller than that of the window layer. A light absorption layer formed of a semiconductor in a mesa shape on the window layer and absorbing the detected light to generate the photoelectrons; and a light absorption layer formed of a p-type compound semiconductor on the light absorption layer,
An electron emission layer that causes the photoelectrons to drift from the light absorption layer, a first electrode that is formed by connecting a metal or an alloy on the electron emission layer, and is permeable to the photoelectrons, and a window layer that is made of a metal or an alloy. And a second electrode formed so as to be connected to the upper surface of the peripheral portion of the electron tube. 2. The first electrode is formed in a pattern by a metal or an alloy being substantially evenly distributed on the electron emission layer, and the electron emission layer is exposed substantially uniformly. The electron tube according to claim 1. 3. The electron tube according to claim 1, wherein a contact layer made of an n-type compound semiconductor is formed between the electron emission layer and the first electrode. 4. In _x Ga _1-x As _y P _1-y (0 <x <1,0 <y <1) in which the light absorption layer is lattice-matched with the window layer and the electron emission layer.
The electron tube according to any one of claims 1 to 3, wherein the window layer is made of a compound semiconductor having a bandgap energy larger than that of the light absorption layer or a mixed crystal thereof. 5. The photoabsorption layer is formed of a quantum well structure of at least two kinds of semiconductor multilayer films, and absorbs the detected light between subbands formed in a conduction band of the quantum well structure to generate photoelectrons. The electron tube according to any one of claims 1 to 4, wherein: 6. The electron tube according to claim 1, wherein the transmission type photocathode is a transition electron type. 7. A multiplication means for multiplying secondary electrons of photoelectrons emitted from the transmission type photocathode is provided between the transmission type photocathode and the anode. 7. The electron tube according to any one of 1 to 6. 8. A two-dimensional photoelectron image emitted from the transmissive photocathode corresponding to the two-dimensional optical image of the light to be detected is provided between the transmissive photocathode and the anode to enhance secondary electron enhancement. A multiplying means for multiplying is provided, and the anode is a fluorescent film which emits light by receiving a two-dimensional electron image obtained by multiplying secondary electrons by the multiplying means. 7. The electron tube according to any one of 7. 9. The solid which outputs an electric signal corresponding to the two-dimensional optical image by receiving a two-dimensional electronic image corresponding to the two-dimensional optical image of the detected light incident on the transmission type photocathode on the anode. The electron tube according to claim 1, wherein the electron tube is an imaging device.