Interstitial Cd doping CdTe films by co-sputtering

Abstract

A series of CdTe thin films were grown in a Cd enriched ambient by co-sputtering a Cd–CdTe target. Different concentrations were obtained by changing the relative area occupied by the metallic Cd pieces placed onto the CdTe target. It was observed that the process of electrical conduction is not the same for all the samples. For samples with Cd < 50 at% the electrical conductivity is due to the direct activation of charge carriers from the valence band or from impurity states to the conduction band. For samples with Cd > 50 at% electrical conduction is due to the hopping of carriers from state to state by optimizing the distance of tunneling. Conductivity ( σ) vs temperature ( T ) measurements indicate that electrical conductivity behaves as ln σ α ( T 0/ T ) [1, 4], the Mott law for variable range hopping (VRH) in disordered systems. We think that this change in conductivity occurs because Cd atoms place in interstitial sites, doping the CdTe lattice, after the Cd vacancy ( V cd) are filled.