Research on quantum efficiency of exponential-doping GaN monolayer reflection-mode photocathode with ultra-thin emission layer

In this paper, we present an exponential-doping GaN monolayer reflection-mode photocathode whose emission layer is composed of few GaN monolayers with different doping concentrations. To understand its optoelectronic emission performance, the quantum efficiency formula of exponential-doping GaN photocathode with ultra-thin monolayers as the emission layer is obtained. Then, we simulate the impact of recombination velocity of AlGaN/GaN ML interface, recombination velocity of GaN ML/GaN ML interface, thickness of emission layer with GaN monolayers, surface escape probability and surface reflectivity on quantum efficiency based on the formula, respectively. The results imply that interface recombination velocity made a significant contribution to quantum efficiency of photocathode. When interface recombination velocity in AlGaN/GaN ML and GaN ML/GaN ML is appropriate, they will promote electrons' escape to the cathode surface and achieve higher quantum efficiency finally. Through our simulation results, a helpful reference can be given for design of exponential-doping GaN monolayer photocathode.