THE INFLUENCE OF NITROGEN ON THE OPTICAL AND ELECTRICAL-PROPERTIES OF SPUTTERED A-SI56GE44-N-H FILMS

The influence of nitrogen concentration below 10(22) cm-3 on the properties of a-Si56Ge44: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) (OMEGA cm)-1 which is one order above the value of nitrogen free films. This N content leads to an enhanced photoconductivity of eta-mu-tau = 5 x 10(-7) cm2/V at maximum compared with eta-mu-tau = 4 x 10(-8) cm2/V without nitrogen.