Electrical and magnetic properties

Abstract

Considerable work has been done on doping ZnSe, ZnTe, MgSe, MgTe and Zn-MgSSe alloy [334, 405]. ZnSe, ZnS, CdSe, and CdS can be doped n}-type more easily than p}-type. Theoretical work shows that Al and Ga form stable deep centers in most II-VI semiconductors, similar to DX} centers in AlGaAs. Chlorine is an effective n-type dopant in ZnSe, and wider bandgap ZnMgSSe alloy[405, and references given there in] and BeMgZnSe alloy [406]–[408]. Chlorine doped ZnSe epilayers have been grown by conventional MBE as well as by GSMBE. In the recent growth of Cl doped ZnSe by GSMBE, Ho and Kolodziejski [405] used an effusion source of solid anhydrous ZnCl2. The effusion cell temperature was varied from 140°C to 320°C. The Cl concentration obtained at the highest effusion cell temperature was ~ 1021 cm–3. The growth rate remained constant at about 0.6 μm/hr up to 280∘C but decreased abruptly at 300∘C. The reason for the abrupt decrease is not understood. The PL of the Cl doped samples was dominated by donor bound excitons for Cl concentrations ⩽ 4 × 1018 cm–3. No deep level PL was observed. The intensity of the donor bound excitonic PL increased with Cl concentration up to 1 x 1017 cm–3 and then started decreasing. For Cl concentration of 8 × 1019 cm–;3, the donor bound excitonic PL disappeared and a broad band due to deep levels was observed. The broad band extended from 1.8 to 2.4 eV.