Identification of the shallow donor state in Sb doped ZnO by photoluminescence excitation spectroscopy

Abstract

Photoluminescence excitation (PLE) spectroscopy was used to investigate the optical properties of the recently discovered 3364.3 meV antimony-related donor bound exciton (D0X) in zinc oxide. By suitable control of the growth conditions, we achieved samples in which the Sb-related donor emission was the dominant near-bandgap luminescence feature. Resonant excitation using a tunable UV source enabled the observation of the two electron transitions of the donor bound exciton, enabling the direct determination of the binding energy of the Sb donor at 42.2±0.5 meV, the lowest value yet reported for a donor in this material. The two electron transitions exhibit an unusual blue shift with increasing temperature, which is explained in terms of thermalization of excited states of the D0X initial state. The D0X excited states were probed by PLE and follow the trends of conventional shallow group III donors such as Al, Ga, and In.