Compensation mechanism of bromine dopants in cadmium telluride single crystals

Publication date: 1 April 2015
Source:Journal of Crystal Growth, Volume 415
Author(s): I.V. Gorichok , P.M. Fochuk , Ye.V. Verzhak , T.O. Parashchuk , D.M. Freik , O.E. Panchuk , A.E. Bolotnikov , R.B. James
Cadmium telluride single crystals, doped by Bromine, were grown by Bridgman method and annealed under cadmium overpressure (P Cd=10²−10⁵ Pa) at 800–1100K. Their electrical properties at high- and low-temperature have been investigated. The influence of impurities on the crystal electrical properties has been analyzed by using the defective subsystem model, which includes the possibility of formation of point intrinsic (${\mathrm{V}}_{\mathrm{Cd}}^{2-}$, ${\mathrm{Cd}}_{\mathrm{i}}^{2+}$, ${\mathrm{V}}_{\mathrm{Te}}^{2+}$, ${\mathrm{Te}}_{\mathrm{i}}^{2-}$) and replacement defects (${\mathrm{Br}}_{\mathrm{Te}}^0$, ${\mathrm{Br}}_{\mathrm{Te}}^{+}$), and also point defects complexes (${\mathrm{Br}}_{\mathrm{Te}}^{+}{\mathrm{V}}_{\mathrm{Cd}}^{2-}$), (2Br⁺ Te VCd ⁻)⁰. It was established that the concentration dependence between free charge carriers and annealing process parameters (n(T), n(P Cd)) are determined by two dominant defects −BrTe ⁺ and (2Br⁺ Te V²⁻ Cd)⁰. Their content varies with the annealing temperature and the vapor pressure of the component; the concentration of other defects is much smaller and almost does not influence the electron density.