Reduction of dislocations in GaN films on AlN/sapphire templates using CrN nanoislands

We report significant reduction of threading dislocations in GaN films grown by hydride vapor phase epitaxy on AlN/sapphire templates by employing CrN nanoislands on the AlN. High quality GaN films with very small twist mosaic as well as small tilt mosaic have been grown on the AlN/sapphire templates, which had small tilt but very large twist mosaic. The CrN nanoislands were formed by nitridation of a thin Cr film deposited by sputtering on the AlN/sapphire template, where the AlN/sapphire template was prepared by metal organic vapor phase epitaxy. The full width at half maximum values of x-ray rocking curves from the GaN film with the CrN were 114, 209, and 243 arc sec for (0002), (10-12), and (11-20) reflections, respectively, while those of the GaN film without the CrN were 129, 1130, and 1364 arc sec, respectively. Evaluation of total dislocation density of the GaN films by plan view transmission electron microscopy revealed that the dislocation density was reduced to 2.7× 108 from 6.4× 109 cm-2 by employing the CrN nanoislands. The CrN nanoislands play a key role in reducing the threading dislocations by masking the propagation of dislocations as well as by bending the dislocations.