The origin of shape, orientation, and structure of spontaneously formed wurtzite GaN nanorods on cubic Si(001) surface

Shetty, Satish and Kesaria, Manoj and Ghatak, J. and Shivaprasad, S. M. (2013) The origin of shape, orientation, and structure of spontaneously formed wurtzite GaN nanorods on cubic Si(001) surface. Crystal Growth and Design, 13 (6). pp. 2407-2412. ISSN 1528-7483

Abstract

We elucidate the atomistic level details of the formation of 1-D GaN nanostructures on Si(001) by molecular beam epitaxy. In a multitechnique study, we understand the epitaxy and role of the unintentional interfacial SiNx layer in determining the shape, structure, and organization of the nanofeatures. The 1-D GaN features are seen to be m-faceted and grow along the Si(111) planes and thus are tilted with a 4-fold symmetry on the cubic Si(100) surface. The interfacial mismatch induced dislocations are shown to provide the nucleation centers for the spiral 1-D growth, while their local density determines their evolution into solid rods, tubes, or c-tubes. The unintentional interfacial nitridation of the substrate forms discontinuous amorphous mounds that provide the epitaxial contact to the substrate and also laterally isolate the rods/tubes, enabling them to grow laterally in their equilibrium hexagonal wurtzite structures. We consolidate the results into a schematic model to unveil the underlying mechanism and demonstrate the subtle relationship between the kinetics of growth and the interfacial properties.