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