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Published online by Cambridge University Press: 10 February 2011
To determine the effect of growth conditions on AlN film morphology, we investigated several AlN films grown on sapphire by MOCVD with various V/III ratios. Transmission electron microscopy was used to characterize the film's crystalline quality and defect morphology. TEM results show that the resulting film morphology depends on the V/III ratio. Films grown with NH3 flow rates below 170 sccm have high crystalline quality. In contrast, we observe columnar growth and secondary interfaces in films grown with NH3 flow rates at or above 170 sccm. The secondary interfaces are likely to be inversion domain boundaries (IDBs) and may be associated with strain relaxation. We discuss the V/III ratio's effect on crystalline quality, surface roughness, and IDB and columnar structure formation.