Relaxation to hopping conductivity in sulfur-doped hydrogenated amorphous silicon

Abstract

Hydrogenated amorphous silicon–sulfur alloy (a-SiSx:H) films were rapidly cooled to a temperature at which electrical conduction is normally achieved by a hopping process. In the rapidly cooled state of sulfur-doped hydrogenated amorphous silicon (a-SiS:H) with approximately 0.5 at.% S, the conductivity follows the activated process that dominates at higher temperatures. With time at low temperatures, the conductivity gradually increases and the mechanism is probably hopping conduction. The time dependence of this increase in conductivity is consistent with a stretched-exponential function with a thermal activation energy of about 0.2±0.1 eV and a stretched-exponential exponent of approximately 0.8 independent of temperature.