Influence of varied doping structure on the photo-emission of reflection-mode photocathode

The built-in electric fields formed in varied doped GaAs photocathode may promote the transport of electrons from the bulk to the surface, thus the quantum efficiency of varied doped cathode can be enhanced remarkably. But the really reason of this enhancement, which may be either the increase in the amounts of electrons reaching the surface, or the increase in the energy of the electrons arriving at the surface, is not clear at present. In this paper, the electrons energy distributions in varied doped photocathode and uniformed doped photocathode before and after the electrons escape from the cathode surface were analyzed, and the amounts of the electrons escaped from the surface in different case were calculated for the two kinds of photocathode. The analysis results according to the experimental result indicate that, the varied doping structure may not only increase the amounts of the photoelectrons arriving at the surface, but also cause an offset of the electrons energy distribution to high energy, and which is the root reason for the enhancement of the quantum efficiency.