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Title: The possibly important role played by Ga{sub 2}O{sub 3} during the activation of GaN photocathode

Three different chemical solutions are used to remove the possible contamination on GaN surface, while Ga{sub 2}O{sub 3} is still found at the surface. After thermal annealing at 710 °C in the ultrahigh vacuum (UHV) chamber and activated with Cs/O, all the GaN samples are successfully activated to the effective negative electron affinity (NEA) photocathodes. Among all samples, the GaN sample with the highest content of Ga{sub 2}O{sub 3} after chemical cleaning obtains the highest quantum efficiency. By analyzing the property of Ga{sub 2}O{sub 3}, the surface processing results, and electron affinity variations during Cs and Cs/O{sub 2} deposition on GaN of other groups, it is suggested that before the adsorption of Cs, Ga{sub 2}O{sub 3} is not completely removed from GaN surface in our samples, which will combine with Cs and lead to a large decrease in electron affinity. Furthermore, the effective NEA is formed for GaN photocathode, along with the surface downward band bending. Based on this assumption, a new dipole model Ga{sub 2}O{sub 3}-Cs is suggested, and the experimental effects are explained and discussed.
Authors:
 [1] ;  [2] ; ;  [3] ; ; ;  [1]
  1. School of Information Science and Engineering, Shandong Provincial Key Laboratory of Network based Intelligent Computing, University of Jinan, Jinan 250022 (China)
  2. (China)
  3. Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094 (China)
Publication Date:
OSTI Identifier:
22494736
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ADSORPTION; AFFINITY; ANNEALING; CESIUM; CLEANING; DEPOSITION; DIPOLES; GALLIUM NITRIDES; GALLIUM OXIDES; MATHEMATICAL SOLUTIONS; OXYGEN; PHOTOCATHODES; PRESSURE RANGE NANO PA; QUANTUM EFFICIENCY; SURFACES