Photoemission of Semiconductor Photocathodes for current quantization

The SI system was redefined, and the ampere was defined based on the elementary charge of a single electron. Different devices have been studied to conform to the new definition for practical application. In contrast with a single-electron transistor (SET) that can count individual electrons, a photocathode electron gun-based device that measures a group of electrons is being proposed, which can provide large current several orders higher than SET. A photocathode is an electron source that plays a critical role in the device. This paper studies the photocathodes' photoemission process and quantum efficiency (QE). A revised theoretical expression of QE has been obtained, which agrees well with the simulation and experimental data. It covers the photoemission situation from minimum to saturation with different thicknesses of the buffer layer.