Donor-acceptor pair recombination in non-stoichiometric ZnO thin films

The stoichiometry of pulsed-laser deposited, nominally undoped ZnO thin films can be controlled via oxygen partial pressure during growth. Samples grown under zinc-rich conditions at pressures below 0.02 mbar show the formation of a donor-acceptor pair recombination at 3.104 eV. Temperature- and excitation-dependent photoluminescence studies revealed structural defects, namely zinc interstitials and zinc vacancies, with donor and acceptor binding energies of E-D = 40 meV and E-A = 320 meV, respectively, to be accountable for this recombination. The findings were confirmed via calculations within the quantum defect model. (C) 2009 Elsevier Ltd. All rights reserved.