Microstructure of GaN films grown by metalorganic chemical-vapor-deposition (MOCVD) onc-sapphire substrates has been accessed as a function of post-growth rapid thermal annealing (RTA) temperatures from 600 °C to 800 °C. The influence of the thermally modified, near-surface crystalline quality on sputtered WSi contact to GaN was also evaluated. Similar planar defects were observed in all heat treated samples; only their density differed. Our analyses demonstrated a strong relationship between the improved GaN crystal quality and postgrowth high-temperature thermal processing. The density of the near-surface defects was lowered by 61&percent; as the annealing temperature was raised from 600 °C to 800 °C. Depression of the near-surface defects encouraged development of the &bgr;-W2Ninterfacial phase and promoted metal-semiconductor interface smoothness. ©1997 American Institute of Physics.