CuGaS2 films grown by physical vapour deposition have been studied by photoluminescence (PL) spectroscopy, using excitation intensity and temperature dependent analyses. We observe free and bound exciton recombinations, three donor-to-acceptor (DA) transitions, and deep-level transitions. The DA transitions at ~ 2.41 eV, 2.398 eV and ~ 2.29 eV are attributed to a common donor level ~ 38+-5 meV and three shallow acceptors at ~ 76 meV, ~ 90 meV and 210 meV above the valence band. This electronic structure is very similar to other chalcopyrite materials. The donor-acceptor transitions are accompanied by phonon replicas. Cu-rich and near-stoichiometric material is dominated by the transitions due to the acceptor at 210 meV. All films show deep-level transitions at ~ 2.15 eV and 1.85 eV due to broad deep defect bands. Slightly Cu-deficient films are dominated by intense transitions at ~ 2.45 eV, attributed to excitonic transitions and the broad defect transition at 2.15 eV.
@article{arxiv.2311.00645,
title = {Composition dependence of electronic defects in CuGaS2},
author = {Damilola Adeleye and Mohit Sood and Michele Melchiorre and Alice Debot and Susanne Siebentritt},
journal= {arXiv preprint arXiv:2311.00645},
year = {2025}
}