Shallow donor states of Ag impurity in ZnSe single crystals

The Hall coefficient, electrical conductivity and electron mobility are investigated in Ag-doped n-ZnSe single crystals at temperatures between 8 and 500 K immediately after doping the samples and after storing them for 5 years under normal room conditions in darkness. The formation of donor-type Agi interstitial defects stimulated by time is found for the first time. After 5 years storage, the samples show a dramatic increase in the electrical conductivity, free electron concentration and concentration of shallow donors. A model that explains these changes by the displacement of Ag ions into interstitial sites due to lattice deformation forces is proposed. The formation of an Ag-donor impurity band in n-ZnSe:Zn:Ag crystals stored at room temperature is also studied.