Initial stage of GaN nucleation on [formula omitted]30°-Ga reconstructed 4H-SiC( [formula omitted]) Si by molecular-beam epitaxy

Abstract

Gallium nitride (GaN) initial nucleation kinetics by the influence of SiC(0 0 0 1) Si surface structure has been investigated. The Ga induced √3×√3 R 30° and 3×3 surface reconstructions are found to be more efficacious for GaN growth. During the initial stage of GaN/4H-SiC(0 0 0 1) Si growth by molecular-beam epitaxy, coherent polygon islands grow wide (∼40 nm) along the lateral directions. These coherent islands develop 2D growth through early coalescence as evidenced by the in situ reflection high-energy electron diffraction observation. The control of Ga-adatom migration and the adsorption of 1/3 and 1 monolayer (ML) of Ga-adatom govern the surface morphology of the GaN layers. The bulk surfaces of (1×1) and (2×1) introduces incoherent nuclei, resulting in a delay of GaN coalescence, exhibits rough growth front and poor surface morphology.