High-temperature electrical conductivity of codoped ZnS and CdSe

Systems of binary compounds containing two types of foreign atoms are complicated. In this work we are interested in high-temperature electrical conductivity (HTEC) behaviour of ZnS and CdSe crystals codoped with two impurities (Cu and Cl or In). We tried to find common behaviour and common features in HTEC isobars of these systems. We were also interested in the temperature regions of forming associates between these dopants. At a temperature T=500degreesC, thermodynamic equilibrium between defects in ZnS:Cu:Cl is achieved. For HTEC isobars, three temperature regions with different dominating defects for ZnS:Cu:Cl, CdSe:Cu:In and CdSe:Cu:Cl can be observed. The low-temperature region characterizes the reactions between associates of dopants and single defects with an activation energy DeltaE=1.5 eV for ZnS:Cu:Cl and DeltaE=1.05 eV for CdSe:Cu:In. In the HTEC isobar region, the donor action of both dopants is observed with close to zero or even negative activation energy of HTEC isobars. (C) 2003 Elsevier B.V. All rights reserved.