Comparative study of Al(x)Ga(1-x)As/GaAs photocathodes with different aluminum concentrations by surface photovoltage spectroscopy.

The influence of aluminum concentration in an Al(x)Ga(1-x)As window layer on the performance of Al(x)Ga(1-x)As/GaAs photocathodes was investigated. Three types of transmission-mode photocathode materials with different aluminum concentrations were designed for the comparative research. The surface photovoltage technique was applied to prepare samples. After the Cs-O activation process, spectral response curves of Al(x)Ga(1-x)As/GaAs photocathodes were obtained. Comparative studies show that a higher aluminum composition in the window layer is beneficial to improve the response of Al(x)Ga(1-x)As/GaAs photocathodes in the shortwave region. The surface photovoltage calculation formula of photocathode materials was put forward and used to obtain key performance parameters of Al(x)Ga(1-x)As/GaAs photocathodes by fitting calculations. Through calculations, the Al(x)Ga(1-x)As/GaAs interface recombination velocity, the minority carrier diffusion length of the window layer, and the emission layer were deduced, and there is a positive correlation between the aluminum composition in the window layer and the Al(x)Ga(1-x)As/GaAs interface recombination velocity, which is negative with the performance of photocathodes.