CRYSTAL-GROWTH AND CHARACTERIZATION OF CDTE DOPED WITH TRANSITION-METAL ELEMENTS

CdTe and Cd0.96Zn0.04Te crystals doped with vanadium, and with other transition elements like cobalt and nickel, have been grown by a vertical asymmetric Bridgman technique. The segregation coefficient of V, determined from the concentration profiles measured along the ingot growth axis, is found between 1.2 and 5.5X10(-2) depending on the initial concentration. SIMS imagery reveals the presence of vanadium precipitates of similar to 20 mu m diameter in the V-rich part of the ingots. As a result of the large V-concentration, the crystals present a mosic crystallographic structure, evidenced by a multipeak spectrum in X-ray double diffraction. An increase in the Vickers micro-hardness of CdTe:V beside pure CdTe was observed and interpreted by considerations upon the bonding lengths. A systematic investigation of the optical absorption, measured at 77 K, was conducted as a function of crystal growth parameters. The observed bands are attributed to d-->d* transitions of V2+ (3d(3)) and V3+ (3d(2)) ions on Cd sites.