Phase control of GaN on Si by nanoscale faceting in metalorganic vapor-phase epitaxy

Abstract

Phase stability of GaN on (1 1 1)–(0 0 1) nanoscale faceted Si is investigated. Nanoscale faceting (nanofaceting) is accomplished on a Si(0 0 1) substrate with interferometric lithography and anisotropic wet etching. By relying on the nucleation and associated lateral growth depending on orientation and crystal structure, spatial separation of a cubic-phase region from hexagonal-phase GaN regions which initiate on the facing Si(1 1 1) sidewalls of a 355-nm period V-grooved Si surface is achieved. The appearance of cubic-phase region is associated with a rapid surface planarization with its principal crystal axes parallel to those of the Si(0 0 1) substrate. The boundary between cubic and hexagonal phases is revealed along the Si(1 1 1) sidewalls and extends from each V-groove to the GaN surface for a 600-nm deposition. The phase separation of GaN selectively grown on a nanoscale faceted Si surface and the comparison of its material properties (photoluminescence and Raman scattering for stress measurement) with those of GaN grown on wide-area Si(1 1 1) and Si(0 0 1) imply that nanofaceting can be utilized for phase control of GaN on a Si(0 0 1) substrate.