JPS61198530A - Electron emission cathode - Google Patents

Abstract

PURPOSE:To facilitate the control of an emitted electron flow and make it possible to reduce an electron emission area and perform integration, by providing an N channel region in the surface of at least a part of a P type semiconductor substrate, and providing a means for emitting electrons from the exposed portion of the substrate. CONSTITUTION:A source 2 of a high-concentration N type region for implanting electrons and an insulator layer 3 made of SiO2 or the like and having a thickness of 0.1mum are provided at one end of a P-Si substrate 1. An Al film, which becomes metal layers as gate electrodes G1.4 and G2.5, is provided. When a positive voltage of 5V or the like is applied to the gate electrode G1.4, an N channel 7 is produced on the boundary between the insulator layer 3 and the semiconductor substrate 1. When a high positive voltage of 10V or the like is applied to the gate electrode G2.5 in addition to the application of the positive voltage of 5V or the like, a potential well right under the gate electrode G2.5 is deepened to accelerate electrons in the N channel 7 so that the electrons reach a semiconductor surface 6 and are emitted into a vacuum. As a result, an electron flow 9 can be generated by applying an accelerating voltage to an anode 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electron emitting cathode that serves as an electron source for vacuum tubes, discharge tubes, and various other vacuum electronic devices.

[Technical background of the invention and its problems] Conventionally, electron emitting cathodes used as electron sources in vacuum electronic devices include:
Broadly speaking, there are hot cathodes and cold cathodes. The hot cathode is a tungsten metal cathode, a thorium tungsten monoatomic layer cathode,
Barium-strontium-calcium oxide cathodes and barium-impregnated cathodes are well known, relatively easy to handle, and widely used in practice.

However, these require heating to a temperature of 1,000 to 2,000°C, and have problems with heat dissipation, heat resistance, power consumption, lifespan, etc., and also have the drawback that the initial velocity dispersion of the extracted electrons is large.

On the other hand, cold cathodes include strong field electron emission cathodes, MgO type cathodes,
Various attempts have been made in the past to use tunnel cathodes, but few have been put to practical use, and they have problems such as large initial velocity dispersion of emitted electrons, noise, and electron beam focusing.

Negative electron affinity cathodes (hereinafter referred to as NEA cathodes), which have been developed in recent years, utilize the P-N junction of semiconductors to allow electrons injected from the N region to the P region to cross the low electron barrier (electron affinity) of the P-type surface. This method uses the phenomenon of radiation being emitted into a vacuum.
It is attracting attention because it can be used at room temperature and has a small initial velocity dispersion of electrons, but it is difficult to stabilize the cathode surface and make the thickness of the P region less than the electron diffusion length, and it requires a bias current. It has problems such as concentration near the cathode, so it has not yet been put into widespread use.

[Object 1-1 of the invention] This invention has been made in view of the above-mentioned points, and provides an electron-emitting cathode in which the emission current can be easily controlled, the electron-emitting area can be reduced, and the cathode can be integrated. It is something.

[Summary of the invention]

That is, the present invention forms an n-channel region on at least a part of the surface of a P-type semiconductor substrate, and provides a part of this n-channel with means for emitting electrons from the exposed portion of the P-type semiconductor substrate described in -I-, This is to obtain an electron emitting cathode.

The electron emitting cathode according to the present invention is a cold cathode, and is similar to the above-mentioned NEA cathode in that it utilizes the negative electron affinity (NEA) of a semiconductor or a state close to it.
The essential difference is that the cathode is not a P-N junction, so there is no need to thin the P region, and there is no concentration of bias current. It can be easily controlled and highly efficient.

Comparing the electron emitting cathode of the present invention with other cathodes, it can be operated at room temperature, has low power consumption, has a small initial velocity dispersion of electrons, and can emit electrons from minute parts of the cathode. It provides performance that could not be achieved in the past, such as the ability to be integrated, and can be manufactured using normal semiconductor technology.

[Embodiments of the invention]

An embodiment of the electron emitting cathode according to the present invention will be described with reference to FIG.

The substrate 1 is a P-type semiconductor, for example, p-3i.
A highly doped N-type region (n+ region) source 2 for injecting electrons is formed at one end of the wafer. An insulating layer 3, e.g. SiO2, is formed on the substrate 1-L and the source 2 to a thickness of e.g.
The insulating layer 3 is formed to have a thickness of 1 μm, and the gate electrode G 4 and the metal layer of the gate electrodes G2 and 5, for example, M
Forms a film. As shown in FIG. 1, these gate electrodes are formed partially overlapping or close to the periphery S of the source 2, and in principle, one gate electrode may be provided, but in the embodiment shown in FIG. 1, two gate electrodes are provided. .

The end 6 of the P-type substrate 1 opposite the source 2 is the surface exposed in vacuum. It is desirable that this surface be clean. The cleaning can be carried out by, for example, folding the crystal in a vacuum, or cleaning the surface 6 by heating in a vacuum, degassing, bombarding, etching, or the like.

Further, the crystal plane index of the surface 6 is preferably (100) in the case of Sl. Furthermore, the surface barrier can be lowered by forming a monoatomic layer of Cs and O or a polyatomic layer of alternating layers of Cs and O on the surface 6''.

When a positive voltage, for example 5V, is applied to the gate electrodes G1 and G4,
An n-channel 7 is formed at the boundary between the insulating layer 3 and the semiconductor substrate 1. Furthermore, when a high positive voltage, for example, IOV, is applied to the gate electrodes G2 and 5, the potential well just below it deepens, and the electrons in the n-channel 7 are accelerated to the right in the figure, reach the semiconductor surface 6, and enter the vacuum. By applying an accelerating voltage to the anode 8, an electron current 9 can be formed. Therefore, the surface 6 becomes an electron emitting surface.

Another embodiment of the electron emitting means according to the present invention is shown in FIG.
, (b) and (C). The same parts as in Fig. 1 are indicated by the same numbers. +21 figure shows gate electrode 10 as 1
The thickness of the insulating layer is made thinner as it approaches the electron emitting surface 6 to deepen the potential well and accelerate electrons toward the electron emitting surface 6. (1)) The figure shows a region 11 in which P-type impurities are ion-implanted into the interface with the insulating layer 3 of the P-type conductor substrate 1 near the electron emitting surface 6, instead of keeping the thickness of the insulating layer constant. This is an example of accelerating and radiating electric current r by forming an electric current r. C.C.
In FIG. 1, an n-channel is formed inside the interface between an insulating layer 3 and a semiconductor substrate 1, and a buried channel 13 is formed by making the semiconductor surface slightly N-shaped in order to increase transfer efficiency.

Another embodiment of the electron emitting cathode is shown in FIG. In this structure, since it is an MO5 structure provided with a source 14 and a drain 15, integration is easy, and a large-area electron-emitting cathode can be fabricated by integrating a large number of electron-emitting surfaces 31.

When applied to an actual electron tube, the electron emitting cathode having the structure shown in FIG. 4 is extremely effective. The same parts as in FIGS. 1 to 3 are designated by the same numbers. In this case, the P-type semiconductor is rod-shaped, needle-shaped, or blade-shaped. In the blade-shaped cathode, a source 14 and a drain 15 can be provided, and electrons can be accelerated by an electric field.

In the explanation of Embodiment 1 below, an example was described in which a DC voltage is applied to the gate electrode, but by applying an AC voltage or a pulse voltage to the gate electrode, the potential well is transiently deepened and electron emission is increased. It is also possible to apply a magnetic field to direct the electrons toward the electron emission surface, thereby increasing the radiation efficiency.

In addition, P-type layer 1 is used as a semiconductor material, and Si is used as an insulating layer material.
Although the example of O2 has been described, other semiconductor materials, especially IIT
It goes without saying that insulating layer materials such as -V group compound semiconductors and various oxides and nitrides can be used. It goes without saying that the device structure may be modified in various ways other than the embodiments described above without departing from the present invention.

Salt 1-1 The electron emitting cathode according to the present invention uses a P-type 16 conductor with low electron affinity and has an MIS or MO3 structure to form an n-channel and allow 1.minute of electric current r to flow on the surface of the P-type semiconductor. This makes it possible to emit electrons extremely efficiently.

Moreover, since electrons can be emitted from the tip of the n-channel, the emission area can be made extremely small. If a large area is required, it is easy to integrate a large number of cathodes having the MO8 structure. Furthermore, since the electron emitting cathode according to the present invention can be operated at room temperature, power consumption is low and the initial velocity dispersion of emitted electrons is small, so it provides a high performance electron emitting cathode for various vacuum electronic devices including vacuum tubes. be able to.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a novel electron-emitting cathode that allows easy control of the emitted electron flow, reduces the electron-emitting area, and facilitates the integration of a large number of cathodes as required. I can do it.

[Brief explanation of drawings]

FIG. 1 is a cathode sectional view for explaining an embodiment of the electron emitting cathode according to the present invention. Figure 2 (al (b) FC+ is the first
Another example explanatory diagram of the figure. FIG. 3 is an explanatory diagram of another embodiment of FIG. 1. FIG. 4 is an explanatory diagram of an embodiment suitable for the actual vacuum tube, vacuum electronic device, etc. shown in FIG. 1. P-type semiconductor substrate 20 + source electrode 3, insulating layer 4, gate electrode G1 5, gate electrode G2 6, electron emission surface 7, n-channel 8, anode 9, radiated electron current 10, gate electrode 11, P-type impurity ion Injection layer 12, N-type layer 13, buried n-channel 14, source electrode 15, drain electrode Figure 1 Figure 2 (α) (b) (C) Third
Figure 4

Claims (4)

[Claims] (1) An n-channel region is formed on at least a part of the surface of a P-type semiconductor, and a part of this n-channel is
1. An electron-emitting cathode comprising means for forming an exposed portion of a shaped semiconductor substrate and emitting electrons from the exposed portion. (2) The n-channel region formed on the surface of the P-type semiconductor substrate is formed by providing an insulator layer on the surface of the P-type semiconductor substrate, providing at least one electrode on the insulator layer, and applying a positive voltage to this voltage. An electron emitting cathode according to claim 1, which is formed by applying an electric current. (3) The means for emitting electrons from the exposed portion of the P-type semiconductor substrate is such that a potential well becomes deep in a portion of the n-channel region that engages with the exposed portion. 2. Electron-emitting cathode according to item 2. (4) The means for deepening the potential well in the portion that engages with the exposed portion of the n-channel region is the insulator layer below the electrode.
A method of dividing the electrode into a plurality of parts and applying a high voltage to the part of the electrode that engages with the exposed part; 4. The electron emitting cathode according to claim 3, which is any one or a combination of structures forming regions.