Electrical conduction studies of hot wall deposited CdSe xTe 1−x thin films

Abstract

CdSe x Te 1− x thin films of different compositions have been deposited on cleaned glass substrates using the hot wall deposition technique under conditions very close to thermodynamical equilibrium with minimum loss of material. The electrical conductivity of the deposited films has been studied as a function of temperature. All the films showed a transition from phonon-assisted hopping conduction through the impurity band to grain-boundary-limited conduction in the conduction/valence band at temperature around 325 K. The conductivity has been found to vary with composition; it varied from 0.0027 to 0.0198 Ω −1 cm −1 when x changed from 0 to 1. The activation energies of the films of different compositions determined at 225 and 400 K have been observed to lie in the range 0.0031–0.0098 and 0.0285–0.0750 eV, respectively. The Hall-effect studies carried out on the deposited films revealed that the nature of conductivity (p or n-type) was dependent on film composition; films with composition x=0 and 0.15 have been found to be p-type and the ones with composition x=0.4, 0.6, 0.7, 0.85 and 1 have been observed to exhibit n-type conductivity. The carrier concentration has been determined and is of the order of 10 17 cm −3. The majority of carrier mobilities of the films have been observed to vary from 0.032 to 0.183 cm 2 V −1 s −1 depending on film composition. The study of the mobility of the charge carriers with temperature in the range of 300–450 K showed that the mobility increased with 3 2 power of temperature indicating that the type of scattering mechanism in the studied temperature range is the ionized impurity scattering mechanism.