Resolving decay-time dependent photoluminescence induced by phonon-dressed excitons in ZnO

Time-resolved photoluminescence (PL) experiments on ZnO crystals have been conducted at room temperature to elucidate the origins of a near-band edge (NBE) emission. A temporal profile of the PL spectra exhibits a two-curve structure with different decaying rates and is reproduced reasonably by a biexponential function, indicating that there are at least two origins with different decay times in the NBE emission. By taking free exciton (FX)-longitudinal optical (LO) phonon interactions into account in the analysis of the PL spectra, the faster and slower decaying emissions are found to be associated with stronger and weaker FX-LO phonon coupling, respectively. We propose that the NBE emissions with different decay times are related to crystal imperfections; the fast-decaying emission originates from the region with a higher density of defects or impurities, while the slower one is from the regions with better crystallinity.

Automated summary

Time-resolved photoluminescence experiments on ZnO crystals reveal the presence of at least two origins with different decay times in the near-band edge emission, which are associated with crystal defects and crystallinity.