Reduction of dislocations in GaN epilayers using templated three-dimensional coherent nanoislands

Low-dislocation-density GaN layers have been grown on 6H–SiC(0001) substrates by molecular-beam epitaxy using high-density (∼4×1011cm−2) self-assembled Stranski–Krastanov GaN nanoislands buffer. The density of dislocations determined from hot-wet chemical etching and atomic force microscopy show that the insertion of coherent nanoislands as a buffer reduces the defect migration from the interface to the GaN epitaxial layers. The dislocation density is dramatically dropped to ∼107cm−2 in GaN layers grown on coherent nanoislands as compared to ∼109cm−2 in the typical GaN layers grown on the AIN buffer.