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 LiZn 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 LiZn acceptor responsible for the OL band is 0.65±0.10 eV. The thermal emission of holes from the LiZn 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.