Temperature effect on the electrical properties of undoped and vanadium-doped ZnTe thin films

Abstract

Vanadium-doped ZnTe films of composition 0 to 10 wt% V, were prepared onto glass substrate by e-beam evaporation of the element in vacuum at ∼8×10 −4 Pa. The effects of various deposition conditions on the electrical properties of the films have been studied in detail. The deposition rate of the ZnTe films was at about 2.05 nm s −1. X-ray diffraction (XRD) study shows that the as-deposited ZnTe films are amorphous in nature. The effects of temperature on the electrical properties of the ZnTe and ZnTe:V films were studied in details. The heating and cooling cycles of the samples are reversible in the investigated temperature range after successive heat treatments in air. Thickness dependence of electrical conductivity is well in conformity with the Fuchs–Sondheimer theory. Temperature dependence of electrical conductivity shows a semiconducting behavior with a spectrum of activation energy. The value of activation energy for undoped ZnTe films do agree well with earlier reported values. Dopant vanadium concentration increases the conductivity of the samples. The composition and thickness dependence of the activation energy as well as thermoelectric power studies were done in the 300–413 K temperature range. The results of d.c. conductivity and thermopower obey an activated conduction mechanism. The thermopower of undoped ZnTe films indicates a p-type conductivity. Thermopower results of ZnTe:V films also suggest that the simultaneous bipolar conduction of both carriers take place.