Formation mechanism of threading-dislocation array in AlN layers grown on 6H-SiC (0001) substrates with 3-bilayer-high surface steps

Abstract

We grew AlN layers on 6H-SiC (0001) substrates with three Si-C bilayer high (0.75 nm) steps. In the AlN layers, most of the threading dislocations (TDs) were arranged in rows. The TD row consisted of arrays of a half-loop dislocation, which was formed by an AlN/SiC interfacial dislocation along the step edges of the SiC substrate surfaces and a TD pair at both ends. The configuration of the interfacial dislocation was highly relevant with two-dimensional AlN nuclei at the initial stage of growth. We concluded that the half-loop dislocation arrays were generated in the AlN nucleus coalescence over the SiC step edges.