Hydrogenated amorphous silicon films prepared in cascaded glow discharge reactors

Abstract

Plasma decomposition of silane by glow discharge in cascade reactors, which we proposed earlier, yields highly resistive a-Si:H films with appreciable photoconductivity in the second reactor of the cascade. These films have since been characterized by transmission and scanning electron microscopy, Auger electron spectroscopy, infrared spectroscopy as well as by measuring conductivity, photoconductivity, thermoelectric power, optical gap, light-induced changes in conductivity (Staebler–Wronski effect) and density of gap states to see in what respect these two types of films differ. These investigations show that, deposition parameters remaining the same in the two reactors, the films obtained from the first reactor are in no way different from what other workers have reported. The films prepared in the second reactor of the cascade, however, have (i) low dark conductivity (10−13–10−12Ω−1 cm−1), (ii) higher activation energy (0.95–1.05 eV), (iii) higher photosensitivity, (iv) higher optical gap (2.0–2.1 eV), (v) less density of states in the gap, and (vi) are less prone to Staebler–Wronski effect.