Comparative research on activation technique for GaAs photocathodes |
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| Authors: | Liang Chen Yunsheng Qian Benkang Chang Xinlong Chen Rui Yang |
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| Institution: | 1. Institute of Optoelectronics Technology, China Jiliang University, 310018, Hangzhou, China;2. Institute of Electronic Engineering & Optoelectronics Technology, Nanjing University of Science and Technology, 210094, Nanjing, China;1. Institute of Optoelectronics Technology, China Jiliang University, Hangzhou 310018, China;2. School of Materials Science and Engineering, Zhejiang University, Zhejiang 310027, China;3. Hengdian Group Tospo Lighting Co., Ltd., Dongyang 310007, China;4. Key Laboratory of Ecophysics and Department of Physics, Shihezi University, Xinjiang 832003, China;5. Department of Physics, The University of Alabama in Huntsville, Huntsville, AL 35899, USA;1. College of Aeronautical Engineering, Bingzhou University, Bingzhou, 256603, China;2. College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 211106, China;1. Institute of Optoelectronics Technology, China Jiliang University, Hangzhou, 310018, China;2. School of Materials Science and Engineering, Zhejiang University, Zhejiang, 310027, China;3. Hengdian Group Tospo Lighting Co., Ltd., Dongyang, 310007, China;4. Key Laboratory of Ecophysics and Department of Physics, Shihezi University, Xinjiang, 832003, China;1. Institute of Optoelectronics Technology, China Jiliang University, Hangzhou, 310018, China;2. School of Physics, Nanjing University, Nanjing, 210093, China;3. North Night Vision Technology Co. LTD., Nanjing, 211106, China;4. School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China;5. Department of Physics, The University of Alabama in Huntsville, Huntsville, AL, 35899, USA |
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| Abstract: | The properties of GaAs photocathodes mainly depend on the material design and activation technique. In early researches, high-low temperature two-step activation has been proved to get more quantum efficiency than high-temperature single-step activation. But the variations of surface barriers for two activation techniques have not been well studied, thus the best activation temperature, best Cs–O ratio and best activation time for two-step activation technique have not been well found. Because the surface photovoltage spectroscopy (SPS) before activation is only in connection with the body parameters for GaAs photocathode such as electron diffusion length and the spectral response current (SRC) after activation is in connection with not only body parameters but also surface barriers, thus the surface escape probability (SEP) can be well fitted through the comparative research between SPS before activation and SEP after activation. Through deduction for the tunneling process of surface barriers by Schrödinger equation, the width and height for surface barrier I and II can be well fitted through the curves of SEP. The fitting results were well proved and analyzed by quantitative analysis of angle-dependent X-ray photoelectron spectroscopy (ADXPS) which can also study the surface chemical compositions, atomic concentration percentage and layer thickness for GaAs photocathodes. This comparative research method for fitting parameters of surface barriers through SPS before activation and SRC after activation shows a better real-time in system method for the researches of activation techniques. |
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