中国物理B ›› 2011, Vol. 20 ›› Issue (4): 47801-047801.doi: 10.1088/1674-1056/20/4/047801

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Spectral transmittance and module structure fitting for transmission-mode GaAs photocathodes

赵静, 常本康, 熊雅娟, 张益军   

  1. Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China
  • 收稿日期:2010-11-21 修回日期:2010-12-15 出版日期:2011-04-15 发布日期:2011-04-15
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 60678043) and the Research and Innovation Plan for Graduate Students of Jiangsu Higher Education Institutions of China (Grant No. CX09B_096Z).

Spectral transmittance and module structure fitting for transmission-mode GaAs photocathodes

Zhao Jing(赵静), Chang Ben-Kang(常本康)†, Xiong Ya-Juan(熊雅娟) and Zhang Yi-Jun(张益军)   

  1. Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China
  • Received:2010-11-21 Revised:2010-12-15 Online:2011-04-15 Published:2011-04-15
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 60678043) and the Research and Innovation Plan for Graduate Students of Jiangsu Higher Education Institutions of China (Grant No. CX09B_096Z).

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摘要： A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Ga1-xAlxAs and GaAs. A gradient-doping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectrophotometer from 600 nm to 1100 nm. The theoretical transmittance is derived and simulated based on the matrix formula for thin film optics. The simulation results indicate the influence of the transition layers and the three thin-film layers except glass on the transmittance spectra. In addition, a fitting coefficient needed for error modification enters into the fitted formula. The fitting results show that the relative error in the full spectrum reduces from 19.51% to 4.35% after the formula is modified. The coefficient and the thicknesses are gained corresponding to the minimum relative error, meanwhile each layer and total thin-film thickness deviation in the module can be controlled within 7%. The presence of glass layer roughness, layer interface effects and surface oxides is interpreted on the modification.

关键词: GaAs photocathode, transmission-mode, optical properties, matrix formula

Abstract: A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Ga1-xAlxAs and GaAs. A gradient-doping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectrophotometer from 600 nm to 1100 nm. The theoretical transmittance is derived and simulated based on the matrix formula for thin film optics. The simulation results indicate the influence of the transition layers and the three thin-film layers except glass on the transmittance spectra. In addition, a fitting coefficient needed for error modification enters into the fitted formula. The fitting results show that the relative error in the full spectrum reduces from 19.51% to 4.35% after the formula is modified. The coefficient and the thicknesses are gained corresponding to the minimum relative error, meanwhile each layer and total thin-film thickness deviation in the module can be controlled within 7%. The presence of glass layer roughness, layer interface effects and surface oxides is interpreted on the modification.

Key words: GaAs photocathode, transmission-mode, optical properties, matrix formula

中图分类号:  (III-V semiconductors)

  • 78.66.Fd
78.20.Ci (Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)) 78.40.Fy (Semiconductors)