PHOTOLUMINESCENCE AND ANNEALING BEHAVIOR OF GA-DOPED CDTE CRYSTALS

Ga-doped CdTe crystals grown by the vertical gradient freeze method were studied by measuring high-resolution photoluminescence (PL) and electrical properties. Comparisons were made for as-grown and annealed samples under Cd saturation. The as-grown samples grown from slightly Te rich melt were of high resistivity (108 Ω cm) although gallium on the Te site alone in CdTe acts usually as a shallow donor. The Cd-annealed samples, on the other hand, were n-type with low resistivity. A new prominent PL line at 1.5841 eV was found in the high-resistivity as-grown crystals. Furthermore, the 1.5841 eV line completely disappeared after Cd annealing. These results suggest that the luminescence center related to the 1.5841 eV line is a Cd-vacancy/gallium associated and is responsible for high resistivity. This is direct evidence to explain the high-resistivity mechanism due to so-called self-compensation in CdTe(Ga). The two-electron transitions in Ga donors measured by PL are also reported. © 1989.