Morphology and photoluminescence improvements from high-temperature rapid thermal annealing of GaN

Rapid thermal annealing of GaN in an Ar or N-2 ambient up to 1100 degrees C is shown to improve surface morphology and photoluminescence intensity. For both ambients the average rms surface roughness as determined by atomic force microscopy decreases from similar to 4 nm on the as-grown material to similar to 1 nm after a 1100 degrees C anneal. The band-edge luminescence intensity was increased by a factor of 4 after a 1100 degrees C anneal in a N-2 ambient and a factor of 2 for annealing at 1100 degrees C in an Ar ambient as compared to as-grown material. The 1100 degrees C anneal improves the ratio of band edge to deep-level luminescence and also reduces the electron concentration and mobility. The reduction in mobility can be explained in terms of a two-band conduction mechanism where defect band conduction dominates at the lower carrier densities or an increase in the free-carrier compensation ratio. (C) 1996 American Institute of Physics.