The Hall effect, electrical conductivity and electron mobility were investigated at temperatures between 55 and 500K in n-ZnSe crystals doped with Cu, Ag or Au. The presence of a small amount of Cu atoms leads to an inversion of the sign of the Hall coefficient at temperatures above 300K. Anomalous temperature dependence of the electron mobility was observed in the samples with low Cu concentration (<0.3at% in the melt). Different characters of the temperature dependences of kinetic coefficients were found for n-ZnSe doped with Ag and Au. These curves were typical for crystals having several donor levels at different energetic depths. Immediately after doping, Ag behaved like a usual compensating acceptor impurity while Au showed amphoteric properties. A model was proposed that explained the anomaly of the temperature dependences of the kinetic coefficients in Cu-doped crystals and the lack of the anomaly in Ag-doped and Au-doped crystals. In accordance with this model and the present experimental data, Cu in n-ZnSe had two charge states, CuZn+ (d10) and CuZn2+ (d9), and two acceptor levels near the valence band. The Ag and Au existed in single-charged states AgZn+ and AuZn+ with d10 electron configuration forming single energy levels near the valence band. Au atoms form mainly interstitial Aui donors at low doping concentrations and substitutional AuZn and AuZn-based acceptors at high doping concentrations. Time stimulation of the amphoteric properties of Ag was considered.

Electron Configuration and Charge State of Electrically Active Cu, Ag and Au Ions in ZnSe. N.D.Nedeoglo, V.P.Sirkeli, D.D.Nedeoglo, R.Laiho, E.Lähderanta: Journal of Physics - Condensed Matter, 2006, 18, 8113-27