Photoemission characteristics of different-structure reflection-mode GaAs photocathodes

Abstract

The quantum yield formula for the reflection-mode GaAs photocathode is revised by taking into account the influencing factors of active-layer thickness and interface recombination velocity. By using the revised quantum yield formula, the experimental quantum yield data of three different-structure reflection-mode GaAs photocathodes grown by molecular beam epitaxy are well fitted to compare the cathode performance parameters. The fitted results show that the GaAlAs buffer layer–based gradient-doping reflection-mode GaAs photocathode can achieve a better photoemission capability in the long-wavelength response region than other reflection-mode uniform-doping ones, which is ascribed to the increased electron diffusion length and electron escape probability, due to the gradient-doping GaAs active-layer on one hand and the decreased interface recombination velocity due to the introduced GaAlAs buffer layer on the other hand.