JPS6369118A - Electron emission element - Google Patents

Abstract

PURPOSE:To obtain with ease an element that functions as an optical switch by attaching electrodes to both ends of a P-type semiconductor substrate, and radiating light to the substrate while impressing voltage between the electrodes so as to emit electrons generated in the substrate by optical excitation from the electron emission surface on one end of the substrate. CONSTITUTION:A metal electrode 2 having an electron emission exit is attached to one end surface of a P-type semiconductor substrate 1, and a work function reducing material layer 4 made of Cs or CsO and the like is deposited to the end surface of the substrate 1 exposed in the emission exit. Then, a plane metal electrode 3 is fixed to the other end surface, and driving voltage to make the electrode 2 into higher potential is impressed between the electrodes 2 and 3. In this state, subsequently, light hv with relation between the light hv and bandgap Eg of the semiconductor made into hv >= Eg is radiated on the surface of the substrate 1. In this way, electrons in the substrate 1 and excited on a conduction band, and accelerated with electric field to cause their emission from the layer 4 surface. To stop the emission, light radiation is stopped to cause high-speed optical switching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron-emitting device that emits photo-excited electrons.

[Prior art and its problems] Conventional electron-emitting devices include those that use avalanche breakdown of a PN junction, those that apply a forward bias to a PM junction and inject electrons into the P layer, and those that use a thin insulating layer made of metal. Elements having a sandwiched structure (MI type), field emission type, surface conduction type, etc. have been proposed.

However, since these conventional electron-emitting devices use a system that generates and emits high-energy electrons in a gaseous manner, electron emission can only be controlled electrically. It was not possible to make a connection between light and electron emission.

[Means for Solving the Problems] An object of the present invention is to provide an electron-emitting device that has a simple configuration and can easily control electron emission using light.

In the electron-emitting device according to the present invention, electrodes are bonded to both ends of a P-type semiconductor substrate, a voltage is applied between the electrodes, and the P-type semiconductor substrate is irradiated with light, whereby the P-type semiconductor is excited by light. It is characterized in that electrons generated within the substrate are emitted from an electron emitting surface at one end of the P-type semiconductor substrate.

[Function] In this way, electron emission can be controlled by light, and since it has an extremely simple configuration consisting of only a P-type semiconductor and an electrode, it can be easily manufactured.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic cross-sectional view showing the structure of a first embodiment of an electron-emitting device according to the present invention.

In the figure, metal electrodes 2 are provided at both ends of the P-type semiconductor substrate l.
and 3 are joined to each other, and the metal electrode 2 has an electron emitting opening formed therein. Further, a work function reducing material layer 4 such as cesium Cs or CsO is formed on the surface of the P-type semiconductor substrate 1 at the electron emission port.

In such a configuration, a driving voltage is applied between the electrodes 2 and 3 to make the electrode 2 a high potential, and in this state, the P-type semiconductor substrate 1 is irradiated with light hυ. At this time, hυ≧Eg(Eg
is the bandgap of a semiconductor), then electrons are excited by light into the conduction band and accelerated by the electric field, resulting in
[! ] Released from the surface of the number-reducing material layer 4. However, high electron emission efficiency can be achieved by setting the work function lowering material layer 4 in a state in which the substantial work function is lower than the conduction band level of the semiconductor 1, that is, in a negative electron affinity (NEA) state.

Also, since electron emission does not occur unless light is irradiated, electron emission can be turned on/off by turning the light on/off.
A high-speed optical switching operation can be obtained.

FIG. 2 is a schematic sectional view showing the configuration of a second embodiment of the present invention.

As shown in the figure, one electrode bonded to the P-type semiconductor substrate 1 is a transparent electrode 5 made of ITO or the like, and light is incident from the transparent electrode 5 side. As a result, as described above, electrons are excited in the semiconductor substrate l, accelerated toward the electrode 2 side, and emitted from the surface of the work function-lowering material layer 4.

Note that although only one electron-emitting device is shown in this embodiment, the invention is of course not limited to this.

For example, a transparent electrode 5 is formed on a glass substrate, a plurality of P-type semiconductor substrates 1 are formed on the transparent electrode 5 in an island shape or insulated and separated, and then an electrode 2 having an electron emitting hole corresponding to each semiconductor substrate 1 is formed. By forming the work function lowering material layer 4, an electron emitting device in which a plurality of electron emitting elements are arranged can be manufactured extremely easily.

FIG. 3 is a schematic diagram of a third embodiment of the present invention.

In the same figure, the electron-emitting device shown in FIG. 2 is connected to a transparent substrate t.
and are separated by an insulating, light-opaque material layer 6. Therefore, by turning ON10 FF the light incident on each electron-emitting element, each electron-emitting element can be driven independently. Further, electron emission efficiency can also be controlled by adjusting the energy of incident light.

[Effects of the Invention] As described above in detail, the electron-emitting device according to the present invention can easily achieve electron emission control using light such as optical switch operation. Furthermore, since the structure is extremely simple, consisting only of a P-type semiconductor and an electrode, manufacturing is extremely easy even if a plurality of devices are arranged.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of a first embodiment of an electron-emitting device according to the present invention, and FIG. , FIG. 3 is a schematic configuration diagram of a third embodiment of the present invention. 1◆...P-type semiconductor substrate 2.3 Clarity/Metal electrode 4...
・Work function lowering material layer 5-... Transparent electrode agent Patent attorney Minoru Yamashita Tairaho 1 Figure 2 Figure 'nv

Claims (1)

[Claims] (1) By bonding electrodes to both ends of a P-type semiconductor substrate, applying a voltage between the electrodes, and irradiating the P-type semiconductor substrate with light, light excitation occurs within the P-type semiconductor substrate. An electron-emitting device characterized in that electrons are emitted from an electron-emitting surface at one end of the P-type semiconductor substrate.