Nonpolar GaN films on high-index silicon: Lattice matching by design

Abstract

We explore theoretically the possibility of growing GaN films in a nonpolar orientation on planar high-index Si($hhk$) substrates. Candidate substrates were identified by requiring that they are well lattice matched, on a length scale of several unit cells, to GaN in the nonpolar $m$-plane orientation. These candidate orientations were then used to construct atomistic models of the GaN/Si($hhk$) interface. Using density functional theory, we then computed the formation energies of these nonpolar interfaces and compared them to those of competing polar interfaces. We find that Si(112) and Si(113) offer potentially favorable substrates for the growth of nonpolar $m$-plane GaN.