HOW TO INDUCE THE EPITAXIAL-GROWTH OF GALLIUM NITRIDE ON SI(001)

Electron cyclotron resonance plasma-assisted molecular-beam epitaxy ha s been used to grow hexagonal and cubic GaN crystal layers on Si(100). By a combined application of in-situ reflection high-energy electron diffraction, X-ray photoelectron spectroscopy and cross-sectional tran smission electron microscopy, the state of the Si(001) surface, the st ructure of GaN grown on this surface and the orientation relationship between substrate and layer were determined. Substrate cleaning, surfa ce reconstruction and carbon surface contamination were found to have a strong effect on GaN growth in the early stage of epitaxy (up to 200 0 Angstrom). While polycrystalline GaN in its hexagonal phase is obtai ned on a clean Si(001) surface, cubic GaN grows epitaxially on a Si(00 1)c(4 x 4) surface covered by small three-dimensional cubic beta-SiC c rystallites.