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

Overview & Synopsis

Dislocation densities in nonpolar GaN films were determined using atomic force microscopy (AFM) by counting pits in the GaN surface revealed by a SiH 4 surface treatment. This treatment increased the number of pits detected by a factor of 2 compared to the untreated surface. AFM and transmission electron microscopy analysis of a series of SiH 4 -treated calibration samples indicated that surface pit and dislocation densities corresponded well up to a dislocation density of ~6 x 10 9 cm -2, above which surface pit overlap meant that dislocation densities determined by AFM were underestimated. For all samples with dislocations densities below 6 x 10 9 cm -2, spatial analysis of the surface pit positions showed that dislocations typically accumulated in bands at island coalescence boundaries.