中国物理B ›› 2009, Vol. 18 ›› Issue (10): 4541-4546.doi: 10.1088/1674-1056/18/10/074

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Distribution of carriers in gradient-doping transmission-mode GaAs photocathodes grown by molecular beam epitaxy

张益军, 常本康, 杨智, 牛军, 邹继军   

  1. Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China
  • 收稿日期:2009-01-11 修回日期:2009-04-07 出版日期:2009-10-20 发布日期:2009-10-20
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos 60678043 and 60801036).

Distribution of carriers in gradient-doping transmission-mode GaAs photocathodes grown by molecular beam epitaxy

Zhang Yi-Jun(张益军), Chang Ben-Kang(常本康)†, Yang Zhi(杨智), Niu Jun(牛军), and Zou Ji-Jun(邹继军)   

  1. Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China
  • Received:2009-01-11 Revised:2009-04-07 Online:2009-10-20 Published:2009-10-20
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos 60678043 and 60801036).

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摘要： The gradient-doping structure is first applied to prepare the transmission-mode GaAs photocathode and the integral sensitivity of the sealed image tube achieves 1420~μ A/lm. This paper studies the inner carrier concentration distribution of the gradient-doping transmission-mode GaAs photocathode after molecular beam epitaxy (MBE) growth using the electrochemical capacitance-voltage profiling. The results show that an ideal gradient-doping structure can be obtained by using MBE growth. The total band-bending energy in the gradient-doping GaAs active-layer with doping concentration ranging from 1× 10^19~cm-3 to 1×10^18~cm-3 is calculated to be 46.3 meV, which helps to improve the photoexcited electrons movement toward surface for the thin epilayer. In addition, by analysis of the band offsets, it is found that the worse carrier concentration discrepancy between GaAs and GaAlAs causes a lower back interface electron potential barrier which decreases the amount of high-energy photoelectrons and affects the short-wave response.

Abstract: The gradient-doping structure is first applied to prepare the transmission-mode GaAs photocathode and the integral sensitivity of the sealed image tube achieves 1420 μA/lm. This paper studies the inner carrier concentration distribution of the gradient-doping transmission-mode GaAs photocathode after molecular beam epitaxy (MBE) growth using the electrochemical capacitance-voltage profiling. The results show that an ideal gradient-doping structure can be obtained by using MBE growth. The total band-bending energy in the gradient-doping GaAs active-layer with doping concentration ranging from 1× 10 19 cm-3 to 1×1018 cm-3 is calculated to be 46.3 meV, which helps to improve the photoexcited electrons movement toward surface for the thin epilayer. In addition, by analysis of the band offsets, it is found that the worse carrier concentration discrepancy between GaAs and GaAlAs causes a lower back interface electron potential barrier which decreases the amount of high-energy photoelectrons and affects the short-wave response.

Key words: GaAs photocathode, gradient doping, molecular beam epitaxy, carrier concentration distribution

中图分类号:  (Photomultipliers; phototubes and photocathodes)

  • 85.60.Ha
61.72.uj (III-V and II-VI semiconductors) 73.50.Gr (Charge carriers: generation, recombination, lifetime, trapping, mean free paths) 73.50.Pz (Photoconduction and photovoltaic effects) 73.61.Ey (III-V semiconductors) 81.15.Hi (Molecular, atomic, ion, and chemical beam epitaxy)