Optical Bias Control of Dispersive Relaxations in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>a</mml:mi></mml:math>-Si: H

Abstract

Relaxation of the photoinduced ir absorption band in $a$-Si: H was studied in the microsecond time domain as a function of cw bias illumination. The decays follow a power law ${t}^{\ensuremath{-}\ensuremath{\alpha}}$ where the dispersion parameter $\ensuremath{\alpha}$ increases with bias illumination. At low temperatures, $\ensuremath{\alpha}$ 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.