Theoretical revision of quantum efficiency formula for thin AlGaAs/GaAs photocathodes

摘要

There exist limitations of conventional quantum efficiency models for both reflection-mode (r-mode) and transmission-mode (t-mode) exponential-doped GaAs photocathodes in some cases. The revised quantum efficiency models of the r-mode and t-mode photocathodes are solved from the one-dimensional continuity equations, wherein the built-in electric field in the GaAs layer and the electrons generated from the AlGaAs layer are considered. According to the revised models, the effects of some relational performance parameters are analyzed, such as the thicknesses of GaAs layer and AlGaAs layer, and the interface recombination velocity on the quantum efficiency for t-mode and r-mode photocathodes in combination with the conventional models. The results show that the main contribution of photoelectrons generated from AlGaAs layer to quantum efficiency in the shortwave (i.e. high incident photon energy) region, depends on the factors including cathode thickness and interface recombination velocity.