Abstract
Thin films of a-Si:H are deposited on substrates at 300°C by a conventional thermal evaporation technique. The electrical conductivity of these films is modified by the addition of antimony giving n-type films. The optical properties of the films are investigated using spectrophotometric measurements of the transmittance and reflectance in the wavelength range 200–3000 nm. Both the refractive index
n and the absorption coefficient
α increase when the Sb content is increased. The absorption edge shifts to lower energies for doped films. The optical gap
E
g is evaluated using three different plots for comparison, namely; (
αhν)
1/2, (
α/
hν)
1/2 and (
αhν)
1/3. The value of
E
g decreases with doping for the three expressions. The Urbach parameter
E
0 is calculated and found to increase with doping from 74 meV for the undoped film to 183 meV for concentrations of 9.4 at.% Sb.