JPS6057173B2 - cold electron emission cathode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A cold electron emitting cathode can be obtained by activating the surface of a P-type layer in a PN junction semiconductor with cesium and oxygen to give it negative electron affinity.

When such a cold electron emitting cathode is used, for example, as a source of a scanning electron beam for an image pickup tube, a control mechanism for electron flow is required. Accordingly, the present invention provides a cold electron emitting cathode in which the emitted electron flow can be easily controlled without consuming power and with a low voltage.
FIG. 1 is a cross-sectional view of Example υ of the present invention, in which an ohmic contact metal thin film 2 is provided on the back surface of an N-type silicon semiconductor substrate 1, and a P layer having a circular cutout 3 in the center is provided on the front surface. A type semiconductor layer 4 is formed.

This P-type semiconductor layer 4 is formed by diffusing appropriate impurities from the surface of the substrate 1, and furthermore, an N-type epitaxial semiconductor layer 5 and a P-type epitaxial semiconductor layer 6 are sequentially grown thereon. I have let you. The peripheries of the epitaxial layers 5 and 6 in the semiconductor described above are etched away, and conductive films such as ohmic contact metal thin films 7 and 8 are formed on the peripheries of the P-type semiconductor layer 4 and the P-type epitaxial semiconductor layer 6, respectively, in an annular shape. In addition, the thin film 2 and the above-mentioned thin film 7 are deposited in an appropriate shape and deposited on the substrate 1;
8 are connected to terminals 9, 10, and 11, respectively. Such a semiconductor device is housed in a vacuum container, an anode 12 is provided opposite to the P-type epitaxial semiconductor layer 6, and cesium and oxygen are adsorbed onto the surface of the semiconductor layer 6 to activate it, thereby generating negative electrons. An electron emitting surface 13 having affinity is formed. In addition, the terminal 9 and the anode 12 and the terminal
Voltage sources 14 and 15 are connected between terminals 9 and 11, respectively, and a variable voltage source 16 is connected between terminals 9 and 10. That is, with respect to the N-type semiconductor substrate 1, a sufficiently high positive potential is applied to the anode 12, an appropriate positive potential is applied to the P-type epitaxial semiconductor layer 6, and a negative potential is applied to the P-type semiconductor layer 4. , the potential can be adjusted arbitrarily. In the above-mentioned device, since a forward voltage is applied to the PN junction formed by the N-type and P-type epitaxial semiconductor layers 5 and 6, the P-type epitaxial Electrons are injected into layer 6.

In addition, since the P-type semiconductor layer 4 acts as an insulating layer for this injected electron flow, the injected electrons are concentrated in the cutout part 3 of the P-type semiconductor layer from a wide range of the N-type substrate 1, and the P-type epitaxial layer is Electrons injected into the layer 6 are emitted from the surface 13 having a negative electron affinity into the vacuum as shown by the arrows and captured by the anode 12. In this case, if a negative potential is applied to the P-type semiconductor layer 4 from the terminal 10, a depletion layer 17 is formed around the periphery of the cutout 3, and the injected electrons are restricted.
Furthermore, as the negative potential is increased, the area where the depletion layer 17 is formed gradually expands and eventually spreads over the entire surface of the cutout 3, so that the injected electrons are completely blocked. Therefore variable voltage source 16
The amount of electrons injected from the N-type semiconductor substrate 1 into the N-type epitaxial semiconductor layer 5 and emitted from the surface of the P-type epitaxial semiconductor layer 6 can be controlled by adjusting the amount of electrons, and does not involve power consumption. , when the negative voltage applied to the P-type semiconductor layer 4 by the voltage source 16 is e, and the emitted electron flow is i, it is possible to obtain the control characteristics as shown in FIG.
can. Furthermore, since the depletion layer 17 described above gradually expands from the periphery of the circular cutout 3 toward the center, its diameter d changes at the same time as the emitted electron flow 1 is controlled. In other words, the density of the electron flow does not change much, and the electron flow is controlled by changing its diameter. Therefore, it can also be used for adjusting the resolution of an image pickup tube, etc. In the above embodiment, the shape of the cutout 3 of the P-type semiconductor layer 4 was circular, but it is obvious that it can be square, rectangular, or any other desired shape. Furthermore, in the drawing, the N-type epitaxial semiconductor layer 5 and the P-type epitaxial semiconductor layer 6 are formed in a wide range outside the cutout 3, but this can be further expanded or reduced. . However, in any case, epitaxial semiconductor layers 5 and 6 are formed on the N-type semiconductor substrate in the above-mentioned cutout.
This requires that a As described above, the cold electron emitting cathode of the present invention has a simple structure and can control the emitted electron flow and the size of its cross section without consuming power. For example, when used as a scanning electron beam source such as an image pickup tube or a cathode ray tube, the electrode structure of the electron gun can be simplified and the beam diameter can be prevented from expanding due to dimensional errors in electrode assembly. .

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, and FIG. 2 is a characteristic curve of the cathode of the embodiment of the present invention.

Claims (1)

[Claims] 1. A central P-type semiconductor layer is formed on an N-type semiconductor substrate, and an N-type epitaxial semiconductor layer and a P-type epitaxial semiconductor layer are sequentially provided on the N-type semiconductor substrate in the cutout part. to form a PN junction, the surface of the P-type epitaxial semiconductor layer becomes an electron emitting surface, and a positive potential is applied to the P-type epitaxial semiconductor layer with respect to the N-type semiconductor substrate, and the center An ohmic contact conductive film for applying a negative potential for controlling the emitted electron flow to the P-type semiconductor layer is connected to the N-type semiconductor substrate and the P-type semiconductor layer.
A cold electron emitting cathode characterized in that it is formed in a type epitaxial semiconductor layer and a P type semiconductor layer.