Electrical transport and optical properties of Zn doped Bi–Se chalcogenide glasses

Abstract

We have investigated the electrical and optical properties of Bi 0.5Se 99.5− x Zn x ( x = 0.1, 0.2, 0.5 and 1) thin films. The temperature dependence of dc conductivity was measured in the temperature range 193–343 K in order to identify the conduction mechanism and to observe the doping effect of Zn on Bi–Se. It shows that the conduction in high temperature region (291–343 K) is due to thermally activated tunneling of charge carriers in the band tails of localized states; and in the low temperature region (193–290 K) conduction takes place through variable range hopping in the localized states near the Fermi level. The optical properties of the thin films have been studied in the wavelength range 300–900 nm, which exhibits that the optical band gap decreases with the addition of Zn to Bi–Se matrix. The decrease in optical band gap has been explained on the basis of density of states and the disorder in the system.