Ya. Goldberg et al., Field and temperature dependencies of the quantum efficiency of GaAs and GaP Schottky diodes, J PHYS-COND, 11(2), 1999, pp. 455-463
An experimental and theoretical study of GaAs and GaP Schottky photodiode q
uantum efficiency is reported. The quantum efficiency was investigated as a
function of temperature in the 80-360 K interval and as a function of elec
tric field in the space-charge region in the 15-50 kV cm(-1) interval. The
photocurrent is found to increase strongly with temperature, by a factor of
three for GaP diodes and by a factor of six for GaAs diodes. We believe th
at this is evidence of a high concentration of imperfections in the space-c
harge region. These imperfections manifest themselves only in photoelectric
properties. Such defects act as traps and capture both photoelectrons and
photoholes. At low temperatures, most of the pairs recombine, but some frac
tion of them escape from the traps due to thermal excitation and give an el
ectric current which rises with temperature. The time of the capture has to
be of the order of the carrier drift time, 10(-11) s. The electric field d
ependence of the quantum efficiency is also evidence of the high trap conce
ntration. We believe that this is due to a field-induced shift of the carri
er energy level in the trap. At high temperature, the photon energy and ele
ctric field dependencies of the photocurrent tend towards saturation.