JPH065199A - Photoelectron emitting surface - Google Patents

Abstract

PURPOSE:To improve the sensitivity of photoelectron emission by sealing the light generated by the plasma emission in a constant area. CONSTITUTION:When the light hnu1 is irradiated to an internal positive electrode 21, a positive hole 41 is excited, and in the case where the optical energy thereof is higher than the potential barrier, the positive hole 41 is filled from the positive electrode 21 to a semi-conductor 11. Internal electrodes 21, 22 are biassed by a power source 31. A large quantity of electron and positive hole are generated by the doubling of electrical collapse, which is generated by the filling of the positive hole 41, and the positive holes 41 are carried in the negative electrode 22 direction. At this stage, the semi-conductor 11 is filled with electron 42 from the negative electrode 22 to restrict the generation of space electric charge to raise the density of carrier in the semiconductor 11, and electronic positive hole plasma exists in the electrical collapse doubling area, and the light emission hnu2 is observed. The light hnu2 is absorbed by the semi-conductor 11 again to generate the photoelectron 43. As a result, the electron 42, which is filled from the negative electrode 22 by the irradiation of the light hnu1, and the photoelectron 43 are synthesized on the positive electrode side surface of the semi-conductor 11 to double the electron.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectron emitting surface which emits electrons into a vacuum in response to incident light.

[0002]

2. Description of the Related Art The existing photoelectron emission surface is based on the idea of emitting photoelectrons directly generated by light irradiation into a vacuum. Moreover, the existing photoelectron emission surface has almost no sensitivity outside the visible range.

[0003]

When the photoelectron emitting surface is applied to the detection of extremely weak light, it is important to increase its detection sensitivity. However, the conventional photoemissive surface is
It was not yet sufficient for these uses. The present invention solves the problems of the prior art by introducing a new principle that has never existed before.

That is, the photoelectron emitting surface of the present invention is not only sensitive to light irradiation to generate carrier electrons, but also has a mechanism for multiplying the carrier electrons incorporated therein, and electron holes generated by the multiplication. New photoelectrons generated by absorbing the light emitted from the plasma participate in the electron-hole plasma, and by further multiplying it, we have realized an unprecedented wide wavelength range, especially high photosensitivity in the infrared range. . In other words, the invention has invented improvement of photoelectron emission sensitivity by photon recycling, and no photoelectron emission surface has been invented based on such a concept.

[0005]

A photoelectron emitting surface according to the present invention comprises a pair of internal electrodes consisting of an internal cathode and an internal anode set in a semiconductor having a carrier concentration of 10 ¹² cm ^-3 or less, and a space between the internal electrodes. Means for applying an electric field to the semiconductor, light irradiation means for irradiating the semiconductor or internal electrode with light, internal cathode means for promoting electron injection from the internal cathode, and light for absorbing light generated from electron-hole plasma. Absorbing means, an optical configuration for reflecting light from a useless direction in order to effectively absorb this light, and photoelectrons generated by plasma emission absorption are allowed to participate in the electron-hole plasma, and electrons are absorbed. A radiation means that radiates into a vacuum after multiplying,
It is characterized by having a structure with an external cathode for trapping emitted photoelectrons.

[0006]

The photoelectron emitting surface according to the present invention is based on a completely different idea from the photoelectron emitting surfaces used so far. The photoelectron emission surface so far is the photoelectron itself generated by light irradiation,
It was realized to discharge in a vacuum. In the present invention, avalanche multiplication is caused by the photocarriers generated by light irradiation, a large amount of electron holes are generated, and not only this large amount of electrons are emitted in a vacuum, but also plasma emission generated at this time is absorbed. The photoelectron emission surface with higher sensitivity was realized by causing photocarriers generated by this light absorption to participate in electron-hole plasma, multiplying, and performing vacuum emission. In other words, a structure for confining light emitted by plasma emission in a certain region is provided (for example, by a reflection film), and photon recycling improves the photoelectron emission sensitivity.

[0007]

EXAMPLES The present invention will be described below with reference to specific examples.

FIG. 1 is an embodiment of a photoelectron emitting surface having the most basic structure of the present invention. The internal anode 2 ₁ is formed on the plate of the high resistance semiconductor 1 ₁ , and the internal cathode 2 ₂ is formed on the remaining surface of the semiconductor 1 ₁ . Is the internal anode 2 ₁ thinned so as to have a sufficient transmittance for light (hν ₁ ),
Alternatively, it is formed in a mesh shape. A potential barrier is formed at the interface between the internal anode 2 ₁ and the semiconductor 1 ₁ . The height of this potential barrier varies depending on the combination of the semiconductor 1 ₁ and the internal anode 2 ₁ , but is approximately 1/2 to 2/3 of the band gap energy of the semiconductor 1 ₁ .

The operation will be described with reference to the band diagram of FIG. First,
The internal anode 2 ₁ is irradiated with light (hν ₁ ). Internal anode 2 ₁
Then, the hole 4 ₁ is excited by the light (hν ₁ ). Since the excited holes 4 ₁ have the same energy as the photon energy of the irradiated light (nν ₁ ), the light (hν ₁ )
If the photon energy is higher than that of the potential barrier, holes 4 ₁ are injected from the internal anode 2 ₁ to the semiconductor 1 ₁ .

Power between the internal electrodes 2 ₁ and 2 ₂ is controlled by the power supply 3 ₁ .
The average electric field strength is 0.5 kV / cm or more and 2.5 kV /
Biased below cm. In this case, the electric field concentration is caused naturally into the vicinity of the inner anode 2 _1, internal anode 2 ₁
The electric field strength in the vicinity of is increased to near the avalanche threshold. When the holes 4 ₁ are injected into this region, the avalanche threshold is lowered and avalanche multiplication occurs. This decrease in the avalanche threshold can be interpreted as avalanche injection. In avalanche multiplication generated by the injection of holes 4 _1, a large amount of electrons and holes occurs. The holes are transported within the cathode 2 _{in two} directions.

At this time, electrons 4 ₂ are injected into the semiconductor 1 ₁ from the internal cathode 2 ₂ in order to suppress the generation of space charges. Therefore, the carrier concentration in the semiconductor 1 ₁ is increased, the electric field in the vicinity of the internal anode 2 ₁ is further increased, and the avalanche multiplication is maintained. In the avalanche multiplication region, electron-hole plasma is present and light emission (hν ₂ ) is observed. The spectrum of this emission depends on the energy of hot electrons, but has a broad spectrum from 500 nm to 900 nm.

Light emitted in the vicinity of the internal anode 2 ₁ (hν ₂ )
Are again absorbed by the semiconductor 1 ₁ and generate photoelectrons 4 ₃ . This photoelectron can also participate in electron multiplication and is further multiplied. As a result, on the surface of the semiconductor 1 _{1 on} the anode side, electrons 4 ₂ injected from the cathode 2 ₂ by irradiation with light (hν ₁ ) and photoelectrons 4 ₃ generated by absorption of light emission (hν ₂ ) are generated. Together, there will be more multiplied electrons.

[0013] As shown in FIG. 1, the semiconductor 1 ₁ surface, and then an alkali metal or an alkaline oxide 5 ₁ adsorption of Cs, etc., and reduces the electron affinity of the semiconductor 1 _1. Therefore, these large numbers of electrons are emitted into the vacuum across the surface barrier. That is, the electrons emitted from the semiconductor 1 ₁ are captured by the external anode 2 ₃ in this case and detected by the ammeter 3 ₃ . The above is the basic configuration and operating mechanism of the photoelectron emitting surface of the present embodiment.

The essence of the photoelectron emission surface of the present invention is not only to multiply and emit the carriers generated by light irradiation, but also to absorb the light from the electron-hole plasma generated at that time to further increase the carriers. And to realize a more sensitive photoemissive surface. Therefore, unlike the embodiment shown in FIG. 1, the control of electron plasma emission is not limited to the mechanism of hole injection from the anode and avalanche injection. However, in this case, it can be realized particularly in a low electric field region and with a simple structure, so that it is a very attractive realization means for application. Therefore, in the following example,
Only those using these means will be introduced.

The internal cathode 2 ₂ and the internal anode 2 ₁ used in these structures will be described. Internal cathode 2 _2, hole injection and from the internal anode 2 ₁ to the semiconductor 1 _1, the occurrence of holes due to avalanche multiplication in the semiconductor 1 within _1, controls the generation of the space charge it makes Therefore, the electrons 4 ₂ must be easily injected from the internal anode 2 ₁ into the semiconductor 1 ₁ . Therefore, the internal cathode 2 ₂ material taking the ohmic junction is suitable. Such materials include AuGe / Ni / Au
Alloys such as AuSn, AgInGe and NiGe are suitable. Furthermore, a semiconductor layer that is heavily n-doped can also be used as an equivalent ohmic electrode.

For the internal anode 2 ₁ , a Schottky electrode material is suitable in order to reduce the work function of the hole for light injection. For example, Al, Au, W, WSi, Ti /
Pt / Au, Ti, Ni, Cr, SnO, InSnO and the like. On the contrary, in order to suppress the thermal injection of holes when the light (hν ₁ ) is not irradiated and to reduce the noise, an ohmic material may be used in reverse. A thin p-type semiconductor layer may be positively inserted. Furthermore, it is also possible to use a pn junction, a Schottky junction, or the like, which can control the injection state of holes by bias.

[0017] For the electron injection from the internal cathode 2 _2, it keeps adding only another word. In the above description, electron injection from the internal cathode 2 ₂ has been made as easy as possible. However, conversely, it is possible to block the electron injection and release the blocking if necessary. In other words, keep the internal cathode 2 ₂ a Schottky electrode. At this time, not only the internal anode 2 ₁ but also the internal cathode 2 ₂ is irradiated with light at the same time, and the electron injection from the internal cathode 2 ₂ to the semiconductor 1 ₁ is to utilize the internal photoelectron emission by light. By doing so, the noise can be further reduced. Furthermore, by making the light irradiating the internal anode 2 ₁ and the light irradiating the internal cathode 2 ₂ different lights, a photoelectron emission current can be obtained as a result of the logical multiplication operation of these lights.

The embodiment of FIG. 3, unlike the previous embodiments, the light (hv _1), rather than being directly irradiated to the inside anode 2 _1, a semiconductor which is different from the surface provided with the internal anode 2 ₁ 1
₁ Irradiates the surface. If the wavelength of the irradiation light (hν ₁ ) is longer than the band edge wavelength of the semiconductor 1 ₁ , the irradiation light (hν ₁ ) can be easily emitted from the semiconductor 1 ₁
To reach the interface between the internal anode 2 ₁ and the semiconductor 1 ₁ . The mechanism after that is the same as described above.
As described above, the irradiation method of light (hν ₁ ) can have various changes. At this time, if the irradiation is performed of the light (hv ₁₎ via a cathode 2 _2, the cathode 2 _2, light h
It must be made to have sufficient transmittance for ν ₁ .

In the embodiment shown in FIG. 4, light (hν ₁ ) is irradiated from the surface on which the internal anode 2 ₁ is provided.
₁ is patterned in the shape of a mesh electrode, unlike the embodiment shown in FIGS. When the irradiation light (hν ₁ ) has a wavelength shorter than the band edge wavelength of the semiconductor 1 ₁ ,
Because the light is absorbed by the semiconductor 1 ₁ very shallow surface, the light (hv ₁₎ is not irradiated only at the interface between the semiconductor 1 ₁ 2 ₁ peripheral internal anode. However, when the wavelength of the irradiation light (hν ₁ ) is longer than the band edge wavelength of the semiconductor 1 ₁ , the light (hν ₁ ) passes through the semiconductor 1 ₁ and is reflected by the internal cathode 2 ₂ . Then, the interface between the internal anode 2 ₁ and the semiconductor 1 ₁ is irradiated. Therefore, the internal anode 2 ₁ be made a mesh instead of a thin film, it is possible to efficiently light irradiation.

The structure shown in FIG. 5 is an example of the case where irradiation of light (hν ₁ ) is performed from the side surface of the semiconductor 1 ₁ substrate. In this case also, the light (hv ₁₎ is a longer wavelength than the band short wavelength of the semiconductor 1 _1, reflected scattered sufficiently inside the anode 2 by using
Light (hν ₁ ) can be applied to the interface between ₁ and the semiconductor 1 ₁ .

As exemplified above, the light (hν ₁ )
The irradiation means to the anode 2 _1, there are various variations. By its approach, part of the light (hv ₁₎ is would be out exit from the semiconductor 1 _1, there is a case where the light use efficiency (hv ₁₎ is reduced. Needless to say, it is desirable to improve the trapping efficiency of plasma light (hν ₂ ).

In the embodiment of FIG. 6, as a device for extending the limit wavelength to the longer wavelength side, the internal anode 2 ₁ and the semiconductor 1 are
Between _1, it is inserted semiconductor 1 ₂ there is a band edge wavelength in a longer wavelength than that of the semiconductor 1 _1. By doing so, the potential barrier formed with the internal anode 2 ₁ is lowered, and it becomes possible to inject holes with light having a longer wavelength.

Finally, the resistivity of the semiconductor will be touched upon. According to the mechanism of the photoelectron emitting surface of the present invention, holes are injected by light irradiation, and electrons are injected for neutralization of the holes, so that the avalanche is maintained and light emission is generated due to the avalanche. It takes a certain amount of time to neutralize the charge, which is called a dielectric relaxation time. The dielectric relaxation time τ is determined by τ = εε ₀ / σ. Here, ε and ε ₀ are the relative permittivity of the semiconductor and the permittivity of vacuum. Further, σ is the conductivity of the semiconductor. Therefore, when the semiconductor has too high resistance, the response speed of this photoelectron emitting surface becomes extremely slow. In addition, increasing the conductivity to obtain the responsiveness does not make sense because the electric field concentration means for the anode applied in the present invention cannot be used. Therefore, the carrier concentration of the semiconductor used for the photoelectron emission surface of the present invention is preferably about 10 ¹² cm ^-3 or less. As another response speed improvement measure,
Injected holes travels to the inside cathode 2 _2, where it is mentioned to thin the semiconductor 1 ₁ of thickness so as to disappear.
In this case, charge neutralization is completed within the transit time of holes between the electrodes, so that the response becomes faster. This thickness is approximately 30 μm or less. Apart from the problem of response speed,
The high-resistance semiconductor used in the present invention may be semi-insulated, and is not affected by the impurities contained for carrier compensation. An example of a semi-insulated semiconductor is C
r: GaA _S , CrO: GaAs, V: GaAs, F
e: InP and the like can be mentioned.

Further, as a feature of the present invention, when light having a two-dimensional spatial distribution is irradiated, it is possible to perform electron emission while preserving the spatial distribution. This is because, since the semiconductor used in the present invention has a high resistivity and an electric field is applied in parallel, there is almost no exchange of charges in the lateral direction of the semiconductor wafer. Thus, the present invention is a completely different photoemissive surface from the previous one,
It is a photoelectron emitting surface that has a simple structure and is sensitive to long wavelengths.

[0025]

According to the present invention, a photoelectron emitting surface having unprecedentedly high photosensitivity to light irradiation, particularly infrared light irradiation, can be realized. Moreover, it is characterized by a simple structure and the ability to store a two-dimensional distribution. In addition, at present, a good photoelectron emission surface in the long wavelength region has not been realized, and its application range is wide.

[Brief description of drawings]

FIG. 1 is a structural diagram of an embodiment of a photoelectron emitting surface.

FIG. 2 is an energy band diagram of a photoelectron emitting surface in an operating state.

FIG. 3 is a structural diagram of an embodiment of a photoelectron emitting surface.

FIG. 4 is a structural diagram of an example of a photoelectron emitting surface.

FIG. 5 is a structural diagram of an embodiment of a photoelectron emitting surface.

FIG. 6 is a structural diagram of an embodiment of a photoelectron emitting surface.

[Reference Numerals] 1 ₁ ... high-resistance semiconductor, 1 ₂ ... semiconductor having a smaller band gap energy than the semiconductor 1 _1, 2 ₁ ... internal anode, 2 ₂ ... inside the cathode, 2 ₃ ... external anode, 3 ₁ ... semiconductor 1
Power supply for applying bias to ₁ 3 ₂ ... Bias power supply for trapping electrons to external anode 3 ₃ Ammeter 41 ₁
Holes injected from the internal electrode 2 _1, 4 ₂ ... injected photoelectrons from the inner cathode, 4 ₃ ... excited photoelectrons by the light hv _2, 5 1 _... alkali, alkaline oxide layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Iida 1 1126, Nomachi, Hamamatsu, Shizuoka Prefecture 1126 Hamamatsu Photonics Co., Ltd. (72) Inventor Sadahisa Warashi 1 1126, Nomachi, Hamamatsu, Shizuoka Prefecture Hamamatsu Photonics (72) Inventor Kenichi Sugimoto, 1126, Nomachi, Hamamatsu, Shizuoka Prefecture 1126 Hamamatsu Photonics Co., Ltd. (72) Inventor, Tomoko Suzuki, 1126, Nomachi, Hamamatsu, Shizuoka Prefecture 1 Hamamatsu Photonics Co., Ltd.

Claims (12)

[Claims] 1. A pair of internal electrodes consisting of an internal cathode and an internal anode set in a semiconductor having a carrier concentration of 10 ¹² cm ⁻³ or less, a means for applying an electric field between the internal electrodes, the semiconductor or the internal Light irradiation means for irradiating the electrode with light, internal cathode means for promoting electron injection from the internal cathode, light absorption means for absorbing light generated from electron-hole plasma, and effective absorption of this light The optical structure is designed to reflect light from a useless direction so that photoelectrons generated by plasma emission absorption are allowed to participate in the electron-hole plasma, the electrons are multiplied, and then emitted into a vacuum. A photoelectron emitting surface having a structure comprising an emitting means and an external cathode for trapping emitted photoelectrons. 2. The light irradiating means is configured to irradiate light on both the interface between the internal anode and the semiconductor and the interface between the internal cathode and the semiconductor. Item 1. The photoelectron emitting surface according to item 1. 3. The photoelectron emitting surface according to claim 1, wherein the semiconductor is a semi-insulating semiconductor. 4. The photoelectron according to claim 1, wherein an average electric field strength of an electric field applied between the internal electrodes is 0.5 kV / cm or more and 2.5 kV / cm or less. Radiating surface. 5. The semiconductor is GaAs or In
The photoelectron emitting surface according to claim 1, which is P or a mixed crystal semiconductor thereof. 6. The at least one of the internal cathode and the internal anode is an ohmic electrode.
2. The photoelectron emitting surface according to any one of 1 to 2. 7. The photoelectron emitting surface according to claim 1, wherein the photoelectron emitting surface is configured to have a pn junction immediately before the internal anode. 8. The photoelectron emitting surface according to claim 7, wherein the pn junction is formed by a heterojunction. 9. The photoelectron emitting surface according to claim 1, wherein the light from the light irradiating means is light having a wavelength longer than the band edge wavelength of the semiconductor. 10. The photoelectron emitting surface according to claim 1, wherein the external cathode as the emitting means and the internal anode are the same electrode. 11. The method according to claim 1, wherein the irradiation of light by the light irradiation unit and the emission of electrons by the emission unit are performed in the same plane of the semiconductor. Photoemission surface. 12. The light irradiation by the light irradiation means and the emission of electrons by the photoelectron emission means are performed in different planes of the semiconductor. Photoemission surface.