Novel synthetic pathways to wide bandgap semiconductors in the Si-C-Al-N system

Epitaxial SiCAlN films with single-phase wurtzite structures were grown by molecular beam epitaxy via reactions of a specifically designed molecular precursor H₃SiCN and Al atoms at 750°C, considerably below the miscibility gap of SiC and AlN at 1900°C. The film growth was conducted directly on Si(111) despite the 19% lattice mismatch between the two materials. Commensurate heteroepitaxy was facilitated by the conversion of native and thermally grown SiO₂ layers into crystalline Si-Al-N-O interfaces in registry with the Si(111) surface. This crystalline interface acted as a template for nucleation and growth of SiCAlN. Integration of wide bandgap semiconductors including AlN and GaN with Si was achieved by this process. Perfectly epitaxial SiCAlN was also grown on 6H-SiC(0001) substrates and exhibited novel crystallographic and physical properties such as hexagonal structures with 2H/2H and 4H/2H SiC/AlN stacking, metastable cubic structures, wide bandgaps in the UV, and extreme mechanical hardness. These properties have been measured by a wide range of characterization techniques and ab initio density functional theory simulations have been used to elucidate the structural and spectroscopic behavior.