Abstract 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.
A PHOTOEMITTER WITH AN IMPROVED INFRARED RESPONSE COMPRISING A SEMICONDUCTIVE LAYER OF A GROUP III-V COMPOUND HAVING A BANDGAP EQUAL TO A DESIRED PHOTOELECTRIC THRESHOLD, A 10-100A THICK FILM OF A SECOND III-V COMPOUND ATOP SAID SUBSTRATE, SAID SECOND III-V COMPOUND NORMALLY HAVING A BANDGAP WIDER THAN THE BANDGAP OF SAID UNDERLYING LAYER, AND ELECTROPOSITIVE METAL IONS ABSORBED WITHIN THE SURFACE OF SAID FILM IN AN AMOUNT SUFFICIENT TO LOWER THE SURFACE WORK FUNCTION OF SAID FILM TO THE DESIRED PHOTOELECTRIC THRESHOLD.
Claim 2
Dependent Claim
82 words
A PHOTOEMITTER WITH AN IMPROVED INFRARED RESPONSE COMPRISING A SEMICONDUCTIVE LAYER OF A GROUP III-V COMPOUND HAVING A BANDGAP EQUAL TO A DESIRED PHOTOELECTRIC THRESHOLD, A 10-100A THICK FILM OF A SECOND III-V COMPOUND ATOP SAID SUBSTRATE, SAID SECOND III-V COMPOUND NORMALLY HAVING A BANDGAP WIDER THAN THE BANDGAP OF SAID UNDERLYING LAYER, AND ELECTROPOSITIVE METAL IONS ABSORBED WITHIN THE SURFACE OF SAID FILM IN AN AMOUNT SUFFICIENT TO LOWER THE SURFACE WORK FUNCTION OF SAID FILM TO THE DESIRED PHOTOELECTRIC THRESHOLD.
Claim 3
Dependent Claim
38 words
A photoemitter according to claim 1 wherein said Group III metals are selected from the group consisting of gallium and indium and said Group V materials are selected from the group consisting of phosphorus, arsenic, antimony and bismuth.