study of the 1.13eV photoluminescence(PL)band in GaAs epilayers grown on St by metal-organic chemical vapor deposition(MOCVD)was made at various temperatures and excitation intensities. The 1.13eV PL band can be explained in terms of the recombination luminescence of the donor-acceptor pair. Changes in PL emission energy and PL intensity as a function of temperature and excitation intensity lead to the identification of a 295meV deep acceptor and a smeV shallow donor.It was verified that the 1.13 eV PL band originates from the recombination luminescence of a St donor on Ga site and the nextnearest neighbor Ga vacancy acceptor.