ELECTRICAL-CONDUCTIVITY AND THE EFFECT OF TEMPERATURE ON PHOTOCONDUCTION OF N-ZNSE P-SI RECTIFYING HETEROJUNCTION CELLS/

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).