Thin films with thickness 100 nm of Ge10+xSe40Te50=x (I ranging from 0.0 to
16.65 at.%,) were formed by vacuum deposition at 1.33 x 10(-4) Pa. The cha
nge in electrical resistivity of the films has been measured using the copl
anar method. The measurements have been carried out in a temperature range
between 400 and 142 K. The values of the electrical activation energies lie
in the range of 0.18-0.38 eV. The optical absorption behavior of these ter
nary thin films was studied from the reflection and transmission. The optic
al band gap was found to be in the range of 0.90-1.11 eV and arose from ind
irect transitions. On the other hand, the width of the band tail E-e was fo
und in the range 0.19-0.32 eV and exhibits opposite behavior. This behavior
is believed to be associated with a defected bond of Te-Te and a cohesive
energy (CE).