Photoluminescence of CuAlxGa1−xSe2 crystals grown by chemical vapor transport

The photoluminescence (PL) characteristics have been studied for the CuAlxGa1−x Se2 chalcopyrite quaternary crystals grown by an iodine transport technique. The PL measurements at 77 K reveal the existence of three types of emission bands, which are attributed to transitions involving localized states: shallow acceptors, deep donors, and deep acceptors, respectively. The origin of the shallow acceptors is tentatively assigned to Se interstitials and that of the deep donors to iodine impurities. All the measured crystals are p type and the hole mobility at room temperature decreases with x (≲0.3).