Defect chemistry in CuGaS_2 thin films: A photoluminescence study

摘要

In this paper, the radiative recombination in CuGaS_2 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-stoichiometric layers, weak excitonic recombination at ～ 2.48 eV and a donor-acceptor line at ～2.4 eV are observed in the low temperature PL spectra. In Cu-rich layers, a donor-acceptor band at ～2.18 eV dominates, while a band at ～ 2.25 eV 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 2 eV in favour of a very broad band at ～1.8 eV. The PL response is discussed within the context of fluctuating potentials in compensated material and compared to available reports in literature.