Abstract

The influence of aluminum concentration in an ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ window layer on the performance of ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ 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 ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ photocathodes were obtained. Comparative studies show that a higher aluminum composition in the window layer is beneficial to improve the response of ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ photocathodes in the shortwave region. The surface photovoltage calculation formula of photocathode materials was put forward and used to obtain key performance parameters of ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ photocathodes by fitting calculations. Through calculations, the ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ 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 ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ interface recombination velocity, which is negative with the performance of photocathodes.

© 2015 Optical Society of America

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