Thermally stimulated current studies of the density of gap states in amorphous silicon

Abstract

Careful thermally stimulated current experiments were carried out on undoped amorphous hydrogenated silicon. We observe two peaks in the TSC profile, one at 120°K and the other at 300°K. We construct a theoretical framework based on the retrapping mechanism to understand this phenomena. The agreement between experiment and the theoretical prediction is good. In contrast the non-retrapping, high field formulation provides a poor fit to the experiment. We deduce that the density of states (DOS) in the gap has a maxima at 0.45 eV in broad agreement with the results of field effect measurements. Deep level transient spectroscopy (DLTS) measurements, which predict a minima in the DOS at 0.4 eV, find no support from our calculations.