Photoemission Characteristics Of Transmissive Variable Composition Doped GaAs Photocathode

The transmission-mode graded-bandgap varied-doping GaAs photocathodes has high response ability in bule-green band,which has a good application prospect in ocean exploration,high energy physics and astronomical observation.In this paper,the optical properties,photoemisson performance,structure design and thickness-fitting software of the transmission-mode graded-bandgap varied-doping GaAs photocathodes,as well as the experimental analysis of different structured photocathodes grown by metel organic chemical vapor depostion method were studied.Firstly,the optical performance formula of transmission-mode graded-bandgap varied-doping GaAs photocathodes was derived based on the theory of thin-film optical matrix.And the influences of optical constants and thickness of films on the photocathodes's optical performance was analyzed.Secondly,based on the optical properties of the photocathode,the quantum efficiency model of the transmission-mode graded-bandgap varied-doping GaAs photocathodes was obtained by solving the one-dimensional continuum equation followed by photoelectron transport.And the influences of each film's thickness on the photo cathodes's quantum efficiency was analyzed.Then,based on the theoretical model of quantum efficiency,the difference of quantum efficiency in the shortwave between graded-bandgap window layer and uniform-bandgap window layer photocathodes was analyzed and compared.Finally,based on the calculation formula of optical properties and the theoretical model of the quantum efficiency,the software for the structural design and thickness fitting of the transmission-mode graded-bandgap varied-doping GaAs photocathodes was prepared by MATLAB GUI function.The photocathodes samples with different structures were designed and grown.The optical properties and the spectral response curves of the photocathode samples were measured,and the performance parameters of photocathode samples were obtained by fitting the experimental curves.The results show that the theoretical model has good experimental fitting effect.The research work in this paper has a guiding significance on the theoretical research and structural design of transmission-mode uniform-bandgap varied-doping GaAs photocathodes.