Activation experiments and quantum efficiency theory on gradient-doping NEA GaAs photocathodes

Abstract

Two gradient-doping GaAs photocathodes were designed and activated, the achieved highest integral sensitivity for the gradient-doping cathode is 2178μA/lm, which is much higher than that of uniform-doping cathode. The increase in the integral sensitivity is attributed to the electric field induced in the active layer of gradient-doping cathode. We analyze the transported mechanism of gradient-doping cathodes and solve the quantum efficiency equations of exponential-doping cathode, which is a special gradient-doping cathode with a constant induced electric field, from the one-dimensional continuity equations. According to these equations, we calculate the theoretical quantum yield of the exponential-doping cathodes, and compare the performance of exponential-doping cathodes with that of uniform-doping cathodes. The theoretical results show that the exponential-doping structure can increase the quantum yield of photocathodes evidently, for the transmission-mode cathodes the increase is even more pronounced.