Thermally stimulated conductivity in a-Si:H doping superlattices

Abstract

Hydrogenated amorphous silicon doping superlattices are utilized to obtain a high metastable concentration of spatially separated electrons and holes trapped in their respective band tails. Thermally stimulated conductivity (TSC) experiments show that the thermal energy required to excite carriers to the transport path decreases with increasing concentration of metastable carriers (N meta). This is in contrast to IR-photoconductivity data which show a fixed threshold for the excitation of band tail carriers to the mobility edge which does not depend on N meta. A model is proposed in which the differences between thermal and optical excitation energies are due to potential fluctuations created by the trapped carriers themselves.