Ultraviolet-emitting ZnO thick layer grown by thermal oxidation with gallium

The ZnO layer with thickness of 1.6 μm in ZnO/ZnGa 2 O 4 composite structure was grown by the thermal oxidation of ZnS substrate with gallium. The optical property of the ZnO thick layer was investigated by time-resolved photoluminescence. A single UV emission around 375 nm with short lifetime was observed at room temperature while the visible emission was absolutely quenched. The UV emission band was composed of the neutral donor bound exciton (D 0 X) and donor-acceptor pair (DAP) emission peaks with large full-width at half-maximums (FWHMs) at 3.367 and 3.318 eV, respectively, at 10 K. However, the intensity of the D 0 X emission was stronger than that of the DAP emission at measuring temperatures of 10–300 K.