Dynamics of band tail holes in amorphous As2Se3: direct measurement of hopping relaxation time

The temperature-dependent hopping relaxation-times are evaluated directly f rom the experimental data of ac photoconductivity measured between 20 and 3 00 K in evaporated amorphous As2Se3. The relaxation time is a constant, 5 x 10(-2) s, between 20 and 150 K and then decreases with increasing temperat ure to 5 x 10(-5) s at 300 K. The dependence of the transport energy on tem perature is estimated by assuming exponential band tail states, is not cons istent with that expected from the de photoconductivity. The temperature va riation of the diffusion coefficient estimated from ac photoconductivity is found to be similar to that of de photoconductivity. (C) 2000 Elsevier Sci ence B.V. All rights reserved.