Annealing dependence of optical and electrical properties of Ga 8As 46Te 46 thin films

Abstract

Amorphous Ga 8As 46Te 46 thin films obtained by vacuum evaporation display an increase in optical energy gap E g with increase in the film thickness. The Ga 8As 46Te 46 film is annealed at different elevated temperatures from 413 to 463 K. The values of the optical gap E g are also found to increase with the annealing temperature up to 443 K, but decrease sharply after further increasing the annealing temperature. The effect of thickness and the annealing temperature up to 443 K on the optical energy gap E g of the film is interpreted in terms of the density of states model proposed by Mott and Davis. The electrical conductivity of as-prepared and annealed films were measured in the 80–300 K temperature range. The electrical results show two types of conduction channel that contribute two conduction mechanisms. The crystalline structures resulting from heat treatment at different temperatures have been identified by transmission electron microscopy (TEM). The electrical results obtained are discussed on the basis of the amorphous–crystalline transformation.