MECHANISM OF PHOTOCURRENT MULTIPLICATION IN AMORPHOUS-SILICON CARBIDE SCHOTTKY CELLS

The mechanism of the photocurrent multiplication for both polarities of an applied voltage (two-way) observed in a simple structure of SnO 2/amorphous silicon carbide/Au has been explained by a model based on electron tunneling through the Schottky barriers. Photoholes trapped in the depletion layers at the electrodes of SnO2 and Au induce tunneling by enhancing the electric field applied to the barriers. The model has been in qualitative agreement with electrical properties measured in the steady state and transient state. The dark current at high applied voltages shows Fowler-Nordheim type conduction. The dependence of the steady-state photocurrent on temperature and light intensity indicates that the photocurrent is controlled by electron injection rather than by trap-controlled recombination in the bulk. The rise and decay properties in the transient photocurrent indicate that the trapping and detrapping rates of photoholes in the depletion layers depend on the light intensity and applied voltage but not on temperature. © 1995 American Institute of Physics.