Study of the distribution of localized states in a-Si:Husing the thermally-stimulated-currents technique

Abstract

Thermally stimulated currents (TSC) in hydrogenated amorphous silicon (a-Si:H) are studied for different initial excitation conditions and various heating rates and are found to show two peaks: one at ≊120 K and another at ≊300 K. The peak near ≊300 K is resolved using two almost identical samples in a bridge configuration. From analysis of the heating rate it would appear that the TSC peaks near ≊120 and 300 K arise from states which lie within 2kT of 0.16 and 0.60 eV below the conduction-band edge, respectively. TSC is reduced considerably after light soaking (Staebler-Wronski effect). It is shown that a peak in the initial occupancy of states caused by the product of a fast-rising g(E) and an exponentially decaying occupancy function near ≊0.16 eV may be responsible for the TSC peak observed at ≊120 K and may not necessarily imply a structure in g(E).