Dependence of effective doping on structural order in hydrogenated amorphous silicon

Abstract

Electrical and structural measurements have been made on intrinsic and phosphorus doped a-Si¦H films deposited by R.F. glow discharge at different substrate temperatures (T_s) in the range (50-400°C). Effective doping, parameterised as ratio of dark conductivity of the doped film to that of the intrinsic film deposited at the same temperature is maximum around 250°C. Gap state density inferred from DLTS results shows an increase beyond 250°C. The average bond angle deviation Δθ in the amorphous network, is also minimum around 250°C and increases for higher T_s. The results bring out a good correlation between effective doping and the bond angle deviation, an important element of the short range order in the amorphous network.