Growth and properties of CdTe:Bi-doped crystals

CdTe:Bi crystals were grown by the vertical Bridgman method, varying the nominal Bi-dopant concentration in the range of 1×1017–1×1019 at/cm3. Bi and Bi1.8−2.3Te precipitates are the most characteristic structural defects in these crystals. Raman spectroscopy studies have shown that Bi traps Te from the CdTe host lattice. Low-temperature photoluminescence in the 1.2–1.6 eV energy region is presented. Several new emissions related to the incorporation of Bi are observed. Semi-insulating CdTe was obtained (ρ=2×1010 Ω cm) for dopant concentration of the order of 1×1017 at/cm3. The resisitivity decreased to values as lower as 1×105 Ω cm for higher concentrations. Photosensitivity studies show an evolution from typical conductivity to shallow acceptor defects-related conduction when the Bi concentration is increased.