S. Darwish et al., ELECTRICAL-CONDUCTIVITY AND THE EFFECT OF TEMPERATURE ON PHOTOCONDUCTION OF N-ZNSE P-SI RECTIFYING HETEROJUNCTION CELLS/, Semiconductor science and technology, 11(1), 1996, pp. 96-102
Electrical and photoelectrical measurements are made at different temp
eratures on heterojunction photovoltaic cells fabricated by vacuum dep
osition of n-ZnSe thin films onto p-Si single crystals. A complete stu
dy of the current as a function of voltage and temperature is carried
out in order to gain fundamental information on trap depth, trap distr
ibution and position of the Fermi level. The results are consistent wi
th space-charge-limited conduction due to an exponentially decreasing
distribution of traps. At low voltages, the dark current in the forwar
d direction varies exponentially with voltage. Under reverse bias, the
conduction process is interpreted in terms of a transition from elect
rode-limited Schottky emission to the bulk-limited Poole-Frenkel effec
t, The values of thermal activation energy for photoconduction and eff
ective density of conducting states are determined and found to be 0.2
2 eV and 4.4 x 10(17) cm(-3), respectively. These values are estimated
from the dependence of photocurrent on temperature at constant illumi
nation with an input power density of 50 mW cm(-2).