Measuring dislocation densities in nonpolar a-plane GaN films using atomic force microscopy

Moram, M A and Johnston, C F and Kappers, M J and Humphreys, C J


Dislocation densities in nonpolar GaN films were determined using atomic force microscopy (AFM) by counting pits in the GaN surface revealed by a SiH4 surface treatment. This treatment increased the number of pits detected by a factor of 2 compared with the untreated surface. AFM and transmission electron microscopy analysis of a series of SiH4-treated calibration samples indicated that surface pit and dislocation densities corresponded well up to a dislocation density of \~6 × 109 cm−2, above which surface pit overlap meant that dislocation densities determined by AFM were underestimated. For all samples with dislocation densities below 6 × 109 cm−2, spatial analysis of the surface pit positions showed that dislocations typically accumulated in bands at island coalescence boundaries.

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Department of Materials
Imperial College London
Royal School of Mines
Exhibition Road
London, SW7 2AZ - UK