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Proceedings Paper

Surface cleaning for negative electron affinity GaN photocathode
Author(s): Jianliang Qiao; Yingpeng Yin; Youtang Gao; Jun Niu; Yunsheng Qian; Benkang Chang
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Paper Abstract

In the preparation process for negative electron affinity (NEA) GaN photocathode, the surface cleanness is very important to activation, it influences the sensitivity and stability of NEA GaN photocathode. The traditional corrosion methods based on oxidizing and dissolving can't remove oxygen (O) and carbon (C) on GaN surface effectively. How to get an ideal atom clean surface is still an important question at present. The cleaning techniques for GaN photocathode was studied by using NEA photocathode activation system and XPS surface analysis system. The experiment sample is p-type GaN doped with Mg, doped concentration is 1.37×1017 cm-3, the transfer rate is 3.08 cm2/V-S, and the thickness of activation layer is 0.51 μm, the substrate is 300 μm thick sapphire. The sample was dealed with chemical cleaning depuration at first. And to get the atom clean surface, the vacuum heat cleaning process was needed. The methods of chemical cleaning and the vacuum heating cleaning were given in detail. According to the X-ray photoelectron spectroscopy of GaN surface after chemical cleaning and the vacuum degree curve of the activation chamber during the heat cleaning, the cleaning effect and the cleaning mechanism were discussed. After the effective chemical cleaning and the heating of 700 Centigrade degree about 20 minutes in ultrahigh vacuum system, the oxides and carbon contaminants on cathode surface can be removed effectively, and the ideal atom clean surface can be obtained. The purpose of heating depuration process is that not only to get the atom clean GaN surface, but also to guarantee the contents of Ga, N on GaN surface stabilize and to keep the system ultra-high vacuum degree. Because of the volatilization of oxide and carbon impurity on the cathode surface, the vacuum degree curve drops with the rising of temperature on the whole.

Paper Details

Date Published: 15 October 2012
PDF: 6 pages
Proc. SPIE 8419, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Sensing, Imaging, and Solar Energy, 841920 (15 October 2012); doi: 10.1117/12.977891
Show Author Affiliations
Jianliang Qiao, Nanyang Institute of Technology (China)
Nanjing Univ. of Science and Technology (China)
Yingpeng Yin, Nanyang Institute of Technology (China)
Youtang Gao, Nanyang Institute of Technology (China)
Jun Niu, Nanyang Institute of Technology (China)
Yunsheng Qian, Nanjing Univ. of Science and Technology (China)
Benkang Chang, Nanjing Univ. of Science and Technology (China)


Published in SPIE Proceedings Vol. 8419:
6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Sensing, Imaging, and Solar Energy
Yadong Jiang; Junsheng Yu; Zhifeng Wang, Editor(s)

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