Optical bias control of dispersive relaxations in α-Si:H

Relaxation of the photoinduced ir absorption band in α-Si:H was studied in the microsecond time domain as a function of cw bias illumination. The decays follow a power law t-α where the dispersion parameter a increases with bias illumination. At low temperatures, a increases linearly with the steady-state carrier density while at high temperatures it saturates at high illumination levels. These results are interpreted as evidence for the bias-controlled tunneling process at low temperatures and multiple trapping process with tail states under the saturation condition at high temperatures.