PHOTOLUMINESCENCE PROPERTIES OF DOPED-CUGASE2 AND UNDOPED-CUGASE2 SINGLE-CRYSTALS

The photoluminescence spectra of undoped- and doped-CuGaSe2 single cry stals have been investigated in the temperature range between 2 K and room temperature. Spectra of undoped crystals can be divided into two types. Type I exhibits only one emission line at 1.675 eV, whereas typ e II shows three mon lines at 1,725, 1.710, and 1.640 eV, which were i dentified as band-to-band and bound-to-fret transitions. Photoluminesc ence of samples doped with Si, Sn, Ge, Zn, Cd, Mg, and B is dominated by the presence of donor-acceptor-pair transitions, because of the for mation of extrinsic donor levels due to the dopants. Al-doped samples exhibited spectra similar to that of undoped samples with peaks shifte d to higher energies leading to the assumption of formation of the qua ternary alloy CuGa1-xAlxSe2 with no Al-related defect levels.