EFFECTS OF GA ADDITION TO CUINSE2 ON ITS ELECTRONIC, STRUCTURAL, AND DEFECT PROPERTIES

Using a first-principles band structure method we have theoretically s tudied the effects of Ga additions on the electronic and structural pr operties of CuInSe2. We find that (i) with increasing x(Ga) the valenc e band maximum of CuIn1-xGaxSe2 (CIGS) decreases slightly, while the c onduction band minimum (and the band gap) of CIGS increases significan tly, (ii) the acceptor formation energies are similar in both CuInSe2 (CIS) and CuGaSe2 (CGS), but the donor formation energy is larger in C GS than in CIS, (iii) the acceptor transition levels are shallower in CGS than in CIS, but the Ga-Cu donor level in CGS is much deeper than the In-Cu donor level in CIS, and (iv) the stability domain of the cha lcopyrite phase increases with respect to ordered defect compounds. Ou r results are compared with available experimental observations. (C) 1 998 American Institute of Physics.