Drift mobility in n– and p–conducting a-Si: H

Abstract

The drift mobility of a series of undoped and doped a-Si: H films has been determined from their steady-state photoconductivity and response time. The drift mobilities at 300 K were 0·1 cm² V⁻¹ s⁻¹ and 5 × 10⁻⁴ cm² V⁻¹ s⁻¹ for electrons and holes, respectively. The activation energies were 0·13 and 0·27 eV. There is no influence of doping up to a doping level of 1000 ppm of either PH₃ or B₂H₆. The temperature dependence of the response time reflects changes in the dominant recombination path. At low temperatures tunnelling processes prevail, but with increasing temperature direct capture of free carriers by dangling bonds becomes predominant.