Electrical and optical properties of gallium vacancy complexes in ammonothermal GaN

Bulk GaN crystals were grown by the acidic ammonothermal method and doped with oxygen at concentrations ranging from 1.5 × 1018 to 2.7 × 1019 cm−3. VGa complexes were detected by Fourier transform infrared (FTIR) spectroscopy. Quantitative comparison with secondary ion mass spectrometry (SIMS) and Hall measurements provides the first experimental evidence for VGa–H–O complexes and shows that these complexes are the dominant compensatory defects, the population of which is controlled by the oxygen concentration. The energy level of these complexes was determined by correlating oxygen concentration with optical absorption and with sub-band-gap cathodoluminescence peaks. The effect of these complexes on device performance is discussed.