GB1335979A - Cold cathode structure - Google Patents

Abstract

1335979 Cathode materials; semi-conductor devices GENERAL ELECTRIC CO 6 Nov 1970 [19 March 1970] 53023/70 Headings H1D and H1K A cold cathode comprises an N-conductivitytype semi-conductor substrate 12 on which is formed an arrangement of conductors 18 delineating electron-emissive areas of the substrate surface between the conductors, and surfaceadjacent P-type regions 28 formed in the substrate underlying the conductors to provide a potential barrier to the flow of electrons to the conductors. Figs. 1, 2 (not shown) illustrate devices to which the above construction may be applied. Supported on an N-type substrate, e.g. zinc sulphide; gallium arsenide; gallium phosphide or silicon carbide; may be a conducting layer (14) of Au or Ag on an intermediate insulating layer (16) of silicon nitride, silicon dioxide or magnesium fluoride, and connecting the conducting layer (14) is an array of parallel conductors (18) forming a conducting layer with apertures (20) on the substrate surface. The conductors form a Schottky barrier and are of high work function metal, e.g. Pd, Au, Ag, Pt and the whole surface may be coated with a layer of low work function material such as caesium or Cs and oxygen alternating layers with a Cs excess. For high electron emission a thin metal film may be applied between the substrate surface and the Cs layer to reduce charge build-up. In Fig. 4 (not shown), region 28 of P-type conductivity is produced on the substrate surface underlying the conductors 18, e.g. by using conductors 18 of material which can be diffused into the substrate. In the Fig. 6 modification an additional surface layer 30 of P-type conductivity is provided over the upper surface of the substrate, e.g. by ion implantation and may be 10 to 300Š deep. Use may be in c.r.t.s; microwave generators, amplifiers, display devices and information processing devices.