The influence of nitrogen on the optical and electrical properties of sputtered a-Si56Ge44:N:H films

Abstract The influence of nitrogen concentration below 10 22 cm −3 on the properties of a-Si 56 Ge 44 :N:H films prepared by dc-magnetron sputtering has been investigated. Optical properties in the strong and weak absorbing region are described in terms of the Tauc-gap and the single-oscillator expression after Wemple and DiDomenico, respectively. All characteristic energies show a dependence on nitrogen content and, excepting the dispersion energy, a dependence on annealing after deposition. Films containing about 10 21 N atoms cm −3 have a dark conductivity of nearly 10 −6 (Ω cm) −1 which is one order above the value of nitrogen free films. This N content leads to an enhanced photoconductivity of ημτ = 5 × 10 −7 cm 2 /V at maximum compared with ημτ = 4 × 10 −8 cm 2 /V without nitrogen.