Excited-state spectroscopy of an effective-mass-like level in Cu-rich CuGaSe2

CuGaSe2 (CGS) epitaxial layers grown by MBE on GaAs substrates are characte rized using photoluminescence (PL). The PL spectra of Cu-rich samples have been shown to display relatively well-resolved near-band-edge transitions. A recombination path appearing at 1.62 eV has been studied in detail using selective excitation of the photoluminescence (SPL). These measurements lea d to the resolution of different transitions to excited states, following a resonant excitation of donor-acceptor pairs. The identification of these s tates is made using the ground state binding energy deduced from the temper ature dependence of the photoluminescence and the acceptor excited states i n ZnSe, the binary II-VI analogue of CuGaSe2. From the binding energies ext racted the excited states are ascribed to the 2s(3/2), 2p(5/2)(Gamma 8) and 3p(3/2) states, respectively. These observations clearly establish the acc eptor nature of the 107 meV center involved in the recombination observed a t 1.62 eV, with an effective-mass-like behavior. (C) 2000 Elsevier Science S.A. All rights reserved.