Improvement of photoemission performance of a gradient-doping transmission-mode GaAs photocathode |
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Authors: | Zhang Yi-Jun Niu Jun Zhao Jing Xiong Ya-Juan Ren Ling Chang Ben-Kang and Qian Yun-Sheng |
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Institution: | Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China |
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Abstract: | Two types of transmission-mode GaAs photocathodes grown by molecular beam epitaxy are compared in terms of activation process and spectral response, one has a gradient-doping structure and the other has a uniform-doping structure. The experimental results show that the gradient-doping photocathode can obtain a higher photoemission capability than the uniform-doping one. As a result of the downward graded band-bending structure, the cathode performance parameters, such as the electron average diffusion length and the surface electron escape probability obtained by fitting quantum yield curves, are greater for the gradient-doping photocathode. The electron diffusion length is within a range of from 2.0 to 5.4 μm for doping concentration varying from 1019 to 1018 cm-3 and the electron average diffusion length of the gradient-doping photocathode achieves 3.2 μm. |
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Keywords: | transmission-mode photocathode gradient-doping Cs-O activation quantum yield |
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