ABSTRACT
CuGaSe2 bulk single crystals have been prepared by the solution method using a CuSe solvent. The top half of the products has the single chalcopyrite phase. The Cu/Ga ratio in this portion is a constant more than unity and the Se/metal ratio a constant less than unity. The electrical and optical properties of the intrinsic defects are investigated by annealing samples in vacuum and Se-atmosphere. Acceptors having activation energies of about 20 and 80 meV are presumably ascribed to Cu-vacancies or coppers in the Ga site, and Ga-vacancies, respectively. Donors having activation energies of about 60 meV are ascribed to Se-vacancies. The conduction band tail spreads with increasing the donor density of Se-vacancies.
