GaZn-VZn acceptor complex defect in Ga-doped ZnO
Identification of complex defect has been a long-sought-after physics problem for controlling the defect population and engineering the useful properties in wide bandgap oxide semiconductors. Here we report a systematic study of (GaZn-VZn)- acceptor complex defect via zinc self-diffusion in Ga-doped ZnO isotopic heterostructures, which were conceived and prepared with delicately controlled growth conditions. The secondary ion mass spectrometry and temperature-dependent Hall-effect measurements reveal that a high density of controllable (GaZn-VZn)- is the predominant compensating defect in Ga-doped ZnO. The binding energy of this complex defect obtained from zinc self-diffusion experiments (~0.78 eV) well matches the electrical activation energy derived from the temperature-dependent electrical measurements (~0.82 eV). The compensation ratios were quantitatively calculated by energetic analysis and scattering process to further validate the compensation effect of (GaZn-VZn)- complex in Ga-doped ZnO. Meanwhile, its energy level structure was suggested based on the photoluminescence spectra, and the lifetime was achieved from the time-resolved photoluminescence measurements. The electron transitions between the (GaZn-VZn)- complex defect levels emit the light at ~650 nm with a lifetime of 10-20 nanoseconds. These findings may greatly pave the way towards novel complex defects-derived optical applications.