Development of A^IIB^VI semiconductors doped with Cr for IR laser application

Electrical and optical measurements obtained with CdSe single crystals, doped with chromium from gas-source CrSe over a wide temperature range (500-1050 °C), are compared with ZnSe annealed in liquid metal (Zn). These annealing processes are intended to control the concentrations of the impurity and the intrinsic defects. Low temperature annealing of CdSe crystals in CrSe atmosphere allows to obtain a high electron mobility up to 9000 cm²/Vs at 80 K and demonstrates the low native defect concentration. A high temperature annealing gives rise to increased electron concentration with decreased mobility. Optical absorption measurements show that at the high annealing temperature effective doping with Cr takes place. The impurity absorption beyond the absorption edge is interpreted by the excitation of Cr⁺⁺ and Cr⁺ deep levels.