Open AccessStudy of spectral response for transmission-modeNEA GaN photocathodes
Author(s) -
Xiaohui Wang,
Benkang Chang,
Yunsheng Qian,
Pin Gao,
Yijun Zhang,
JianTian Qiao,
Xiaojiao Du
Publication year - 2011
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.60.057902
Subject(s) - photocathode , quantum yield , metalorganic vapour phase epitaxy , materials science , yield (engineering) , quantum efficiency , diffusion , optoelectronics , chemical vapor deposition , quantum well , layer (electronics) , electron , optics , physics , nanotechnology , epitaxy , fluorescence , laser , composite material , quantum mechanics , thermodynamics
Transmission-mode GaN photocathodes with the emission layer thickness of 150 nm and the doping concentration of 1.6×1017 cm-3 were grown by metal-organic chemical vapor deposition (MOCVD) and were activated in ultra-high vacuum system. The result was tested by Multi-information test system. The shape of transmission-mode NEA GaN photocathode quantum yield curves looks like the Chinese charocter 门 for "door", the photocathode had flat and high response between 255 and 355 nm, the highest quantum yield of 13% appeared at 290 nm. When the wavelength was less than 255 nm the quantum yield was decreased because of the high absorption coefficient of AlN buffer layer at short wavelengths. The quantum yield was also decreased beyond 355 nm and fell to 3.5% at the threshold of 365 nm, the quantum yield at 385 nm was reduced to 0.1% and the cut-off character of long wave was well shown. The quantum yield formula of transmission-mode GaN photocathode has been solved from diffusion equations, and the main factors affecting the quantum yield mostly, including electron diffusion length, electron escape probability, active-layer thickness and the back-interface recombination velocity, were analysed and discussed. The future work is optimizing the structure of the photocathodes.