Effect of composition on the electrical and structural properties of As–Te–Ga thin films

As30Te70−xGax (x=0.5, 1, 3, 6 and 10 at.%) chalcogenide thin films were studied. Specimens of thickness 2500 Å were used for resistivity (ρ) measurements as a function of temperature (T) in the temperature range from 300 to 443 K. The resistivity (ρ) exhibits an activated temperature dependence in accordance with the relation ρ(T)=ρ0 exp(ΔE/kT). It was found that the activation energy for conduction (ΔE) and room temperature resistivity (ρ300) decrease with increasing Ga content up to 3 at.%. For x greater than 3 at.%, it was found that ΔE and ρ300 increase with increasing Ga content. The results were discussed according to the valence alternation pair (VAP) model and the alloying effect. Thermal annealing above Tg was found to decrease ρ and ΔE. The decrease of ρ and ΔE after annealing at T>Tg was attributed to the amorphous–crystalline transformation. XRD, SAED, TEM and DSC were used to study the structure of the as-deposited and annealed films.