Effects of annealing on the optical bandgap of amorphous Ga₅Se_95-xSb_x during crystallization

Abstract

The optical bandgap of as-deposited and annealed films of amorphous Ga₅Se_95-xSb_x (a-Ga₅Se_95-xSb_x) (where x = 0, 5, 10 and 15) have been studied as a function of photon energy in the wavelength range 400–900 nm. Thin films were induced by thermal annealing for 1 h at a temperature below their crystallization temperatures. It has been found that the optical bandgap increases with increasing annealing temperature. For as-deposited films, it has been found that the optical bandgap and refractive index decrease while the extinction coefficient k increases on incorporation of antimony into the Ga-Se system. The temperature dependence (312–392 K) of dc conductivity of bulk samples of a-Ga₅Se_95-xSb_x has also been reported. It has been found that the decrease in activation energy may be due to the decrease in optical bandgap on adding antimony to the present system.