High temperature electrical properties of CdTe(Pb) crystals under Te saturation

Abstract

The point defect equilibrium of CdTe(Pb) single crystals under well-defined Te vapor pressure was investigated up to 1070 K. At 630-900 K these crystals showed p-type conductivity and at higher temperatures - native n-type one. During measurements the hole density reached up to ∼2 × 10 17 cm-3 at 800 K. The main acceptor dominant species, which determined the electrical properties of crystals, was supposed to be the (Pbcd+Vcd2- associate with its level in the gap located at Ev + 0.42-0.45 eV. Above 900 K native electrons began to influence the conductivity type. Three models of point defect structure were used to describe the galvanomagnetic data -(i) frozen defect structure, (ii) defect structure with shallow or deep acceptor levels fixed during thermal cycles and native defects being in three-phase solid-liquid-gas (SLG) equilibrium, and (iii) defect structure without any fixed energy level and defect densities being determined by the SLG equilibrium. The FWM technique confirmed p-type photoconductivity at 300 K, but also revealed bipolar carrier generation at high photoexcitation levels with very fast electron trapping. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.