Abrupt and tunable quenching of photoluminescence in ZnO

The abrupt and tunable quenching of photoluminescence (PL) in bulk ZnO samples is reported, a phenomenon which has been previously observed only in GaN and a few phosphorescent materials. ZnO samples grown by the hydrothermal method contain Li defects responsible for the orange luminescence (OL) band with a maximum at 2.0 eV. The Li_Zn acceptor is well studied, but there is some disagreement in the literature on the value of its ionization energy. Here we show that the ionization energy of the Li_Zn acceptor responsible for the OL band is 0.65±0.10 eV. The thermal emission of holes from the Li_Zn acceptor to the valence band and their subsequent capture by unknown nonradiative centers causes the abrupt quenching of PL, the temperature of which is tunable by excitation intensity.