PHOTOLUMINESCENCE PROPERTIES OF CUINSE2 GROWN BY MOLECULAR-BEAM EPITAXY

Photoluminescence (PL) properties of CuInSe2 thin films with Cu/In rat io ranging from 0.81 to 1.81 grown by molecular beam epitaxy have been investigated for photovoltaic applications. The PL spectra of Cu-rich CuInSe2 epitaxial films unlike those of polycrystalline CuInSe, showe d well-defined emission lines, suggesting that high quality CuInSe2 ep itaxial films have been grown. Such fine PL spectra made the identific ation possible of phonon replicas, in other words, the separation of s uch phonon replicas from substantive emissions. PL properties are foun d to be very sensitive to the growth parameters such as Cu/In ratio an d substrate temperature. A broad peak at lambda similar to 1.45 mu m b ecomes dominant in In-rich films, and excitation power dependence of s uch a broad emission indicated a pair-type radiative recombination, mo st likely the emission due to donor-acceptor pair or their complex.