Radiative recombination via intrinsic defects in CuxGaySe2

A detailed analysis of the radiative recombination processes in CuxGaySe2 e pitaxial layers is presented aiming at an investigation of the intrinsic de fect levels as a function of chemical composition. CuxGaySe2 is grown by me talorganic vapor phase epitaxy to allow a precise control of composition. T emperature and excitation intensity dependent photoluminescence is used to identify different recombination mechanisms and to determine the ionization energies of the defect levels involved. Defect-correlated optical transiti ons in Cu-rich epilayers are described in a recombination model consisting of two acceptor and one donor levels showing ionization energies of (60 +/- 10) meV, (100 +/- 10) meV, and (12 +/-5) meV, respectively. The identifica tion of a shallow compensating donor in CuxGaySe2 and the assignment of the 100 meV state to an acceptor are the most important new aspects in this mo del. Photoluminescence properties of layers showing Ga-rich compositions ar e discussed in a model of highly doped and highly compensated semiconductor s-the model of fluctuating potentials. (C) 2001 American Institute of Physi cs.