The role of Ga supersaturation on facet formation in the epitaxial lateral overgrowth of GaN

Abstract

In this paper, facet formation of (0001) {112¯0} {112¯2} facets during epitaxial lateral overgrowth (ELO) of GaN is investigated for different Ga vapor supersaturations. The ELO was conducted via metalorganic chemical vapor deposition on patterned GaN/sapphire templates with SiO2 masks aligned along the ⟨11¯00⟩ direction of GaN. Scanning electron microscopy was used to characterize the cross section shapes of the ELO GaN islands. A correlation of supersaturation, facet formation, and the shape of the ELO GaN islands is found. It is shown that {112¯2} facets are favored under high Ga vapor supersaturation, while {112¯0} facets are favored under low Ga vapor supersaturation. A qualitative model based on Wulff construction and density functional theory calculation is proposed to illustrate the mechanism of the facet formation of the ELO GaN islands.