Group III-V compound photoemitters having a high quantum efficiency and long wavelength response

摘要

A photoemitter having a high quantum efficiency and a low work function for photoemission, i.e. photoelectric threshold, is formed by depositing a 10-100A film of a wide bandgap Group III-V compound, e.g. gallium phosphide, atop a 0.5-10 micron thick layer of a second Group III-V compound, e.g. gallium antimonide, having a bandgap matching the desired photoelectric threshold. The film surface then is treated with cesium (or cesium and oxygen) to reduce the surface work function of the composite structure to the desired photoelectric threshold. When the Group III-V layer forming the photoemitter is epitaxially grown atop an oriented substrate of a semiconductive material such as gallium arsenide having a bandgap wider than the bandgap of the overlying layer, the resulting photoemitter is transparent only in a range between the bandgap of the substrate and the bandgap of the overlying layer.