Defect chemistry in CuGaS2 thin films:: A photoluminescence study

In this paper, the radiative recombination in CuGaS2 thin films, deposited by metalorganic vapour phase epitaxy (MOVPE), is studied by photoluminescence (PL) spectroscopy. From PL studies of several series of layers grown under various growth conditions, a clear picture emerges of the radiative emission dominating for Cu-rich and Ga-rich layers. For near-stoichiom,etric layers, weak excitonic recombination at similar to 2.48eV and a donor-acceptor line at similar to 2.4eV are observed in the low temperature PL spectra. In Cu-rich layers, a donor-acceptor band at similar to 2.18 eV dominates, while a band at similar to 2.25eV dominates for slightly Ga-rich material. For Ga-rich layers, deviations from the ideal Cu/Ga ratio of more than a few percent strongly quenches the emission above 2eV in favour of a very broad band at similar to 1.8eV The PL response is discussed within the context of fluctuating potentials in compensated material and compared to available reports in literature. (C) 2006 Elsevier B.V. All rights reserved.