Gd-doping effects on properties of amorphous silicon films prepared by electron beam evaporations

Abstract

Gd-doped amorphous silicon films have been prepared by the electron beam evaporation technique, employing the experimental methods of dc conductivity temperature properties, ESR (electron spin resonance) spectra, and optical band gap E_opt measurements. We have investigated the optical and electrical properties of the films. The results show that at 290 K < T < 330 K, hopping conduction in Gd impurity states near Fermi level is predominant, and at 330 K < T < 500 K extended state conduction dominates due to electrons exited from the impurity states. At a Gd concentration of about 1.0 at.% spin density N_s, peak-peak width ΔB_pp and line-shape factor l of ESR spectra change their dependence on Gd contents. The optical gap of the films narrows with increasing Gd contents in the films from 1.68 eV to 0.42 eV. The results were explained on the basis of the partial compensation of Gd atoms for dangling bonds.