Decay kinetics of the defect-based visible luminescence in ZnO

Photoluminescence spectra and decays under pulsed N2 (337 nm) laser excitation were measured for hydrothermally grown bulk and liquid-phase epitaxy (LPE)-grown film ZnO samples within 9-300 K. Temperature dependence of integrated spectra over the exciton and visible spectral regions was evaluated using a model involving standard energy barrier processes. Decay curves measured within a broad time window (10 ns-1 ms) and with extreme signal/background ratio (five orders of magnitude) point to complex decay mechanism in which the exponential and inverse power-law processes can coexist. There is no straightforward interconnection between the observed temperature dependence of integrated visible photoluminescence intensity and its decay shape over the 9-300 K temperature interval.