Abstract
Ge
20Te
80 films were deposited by thermal evaporation technique onto chemically cleaned glass substrates kept at different substrate temperatures (
T
sub=203, 233 and 273
K). The optical data indicated that the width of the localized states tails (
E
e) increases while the optical gap (
E
o) decreases with increasing the substrate and annealing temperature of the investigated films. From the electrical measurements, the activation energy for conduction and the density of localized states at the Fermi energy,
N(
E
F), were obtained. The effects of the substrate and annealing temperature on the width of localized states tails and on the density of localized states at the Fermi level have enhanced each other. The changes in the optical and electrical properties are correlated with the amorphous–crystalline transformations.