A significant reduction in threading dislocations in GaN films grown by hydride vapour phase epitaxy onto AlN/sapphire templates was reported upon using CrN nano-islands on the AlN. High-quality GaN films with very small twist mosaic as well as small tilt mosaic were grown onto the AlN/sapphire templates, which had small tilt but very large twist mosaic. The CrN nano-islands 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 vapour 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 243arcsec for (00•2), (10•2), and (11•0) reflections, respectively, while those of the GaN film without the CrN were 129, 1130 and 1364arcsec, 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 x 108 from 6.4 x 109/cm2 by employing the CrN nano-islands. The CrN nano-islands play a key role in reducing the threading dislocations by masking the propagation of dislocations as well as by bending the dislocations.

Reduction of Dislocations in GaN Films on AlN/Sapphire Templates using CrN Nanoislands. J.S.Ha, H.J.Lee, S.W.Lee, H.J.Lee, S.H.Lee, H.Goto, M.W.Cho, T.Yao, S.K.Hong, R.Toba, J.W.Lee, J.Y.Lee: Applied Physics Letters, 2008, 92[9], 091906