Growth of GaN on a nanoscale periodic faceted Si substrate by metal organic vapor phase epitaxy

Abstract

Growth of GaN on a nanoscale periodic faceted Si substrate by metal organic vapor phase epitaxy is reported. The surface of the Si(001) substrate is patterned with a one-dimensional, 355-nm period array of grooves. Each groove consisted of two facing Si{111} stripe facets separated by upper and lower Si(001) surfaces. GaN deposition on this groove array shows a strong selectivity with epitaxial growth of the hexagonal phase on the Si {111} facets being dominant. The initial stage of GaN growth appears to be amorphous. This is followed by GaN containing a high-density of stacking faults to accommodate the large lattice mismatch strain but the defect density decreases as growth proceeds. Lateral overgrowth from the Si{111} facets toward neighboring Si(001) facets leads to coalescence between GaN from opposing Si{111} facets. These GaN regions have misaligned c-axes and the crystal structure becomes unstable as they merge, resulting in a phase transition from hexagonal to cubic at the coalescence region. Experimental results of GaN grown on a nanoscale faceted Si surface including: nucleation, crystal structure, and lateral growth depending on Si orientation are presented.