Measurements of the electron density in n-type a-Si: H

The density of band tail electrons in n-type a-Si: H, at doping levels between 10−3 and 10−6 PH3, has been measured using a transient-voltage technique on layered samples. At a doping level of 10−3 PH3 a density of 8 × 1016 cm−3 is found which agrees well with ESR data. The results confirm that occupied band-tail states account for only a small fraction of the dopant electrons.