Variable range hopping in hydrogenated amorphous silicon

We study the effect of high-temperature annealing on the conductivity temperature dependence of a-Si:H films. Two types of films were studied: uniform and nanolayered prepared by cyclic repetition of CVD and hydrogen plasma treatment. It is shown that for annealing temperatures above 450C, the low-temperature conductivity obeys the law ln(sigma) = const - (T₀/T)ⁿ, where the exponent is n = 1/2 for uniform and n = 1/3 for layered films. It is argued that the measurements of the conductivity temperature dependence can provide information about the spatial distribution of defects produced by HTA and about the defect creation mechanism.