DECAY OF PHOTOCURRENT FROM THE STEADY-STATE IN A-SIH FILMS

Results are reported on the long-time decay of the photocurrent from the steady state in undoped a-Si:H films. The decay has been studied for various illumination intensities and over a wide temperature range, from 300 down to 50 K. It is found that the long-time photocurrent decay is a strong function of the steady-state illumination intensity when the intensity is low. As the light intensity is increased, the decay gradually approaches a power-law behavior I(ph) approximately t(-beta) and eventually becomes intensity independent. Beta is found to vary nonmonotonically with temperature; a peak appears between approximately 110 and approximately 150 K, depending on the history of the sample as well as on the sample itself. Some possible photocurrent decay models are examined.