Donor-acceptor pair transitions in ZnO substrate material

We investigate the state-of-the-art ZnO substrate material grown by seeded chemical vapour transport. The low-temperature photoluminescence (PL) spectra are dominated by very sharp bound exciton lines, which are followed by two-electron satellite transitions. This identifies the major bound exciton lines as donor related and allows us to derive a binding energy of approximate to40meV for the very similar donors observed here. From a donor-acceptor pair transition at approximate to3.22 eV and its associated band-acceptor line emerging at sample temperatures above 40 K, we calculate the acceptor binding energy as approximate to195 meV. Hall data confirm these findings. (C) 2001 Elsevier Science B.V. All rights reserved.