Blue Photoluminescence and Resonant Raman Scattering in Bulk CuAlSe2 Grown by THM

Blue band edge photoluminescence is observed for the first time in CuASe(2) single crystals grown by THM from the 5 % Cu2Se-rich polycrystalline raw materials. Exciting light energy dependence of the photo-luminescence and resonant Raman scattering exhibits a strong enhancement at 2.601 eV, close to the energy of a bound exciton. A model of the radiative recombination responsible for the newly observed emissions is proposed with a deep donor and a deep acceptor with unclarified origin yet. The value of a small band gap reduction, estimated from the energy shift in the luminescence spectrum, is found to be consistent with that of the In-alloying effect on band gap in the THM-grown CuAlSe2.