Growth of wide band gap optical semiconductors on silicon via novel silicon-aluminum-oxygen-nitrogen and metal boride interfaces

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 band gap semiconductors including AlN and GaN with Si was achieved by this process. Crystalline SiCAlN exhibited novel crystallographic and physical properties such as hexagonal structures with 2H/2H and 4H/2H SiC/AlN stacking, metastable cubic structures, wide band gaps in the ultraviolet region, 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.; Growth of metallic and reflecting ZrB₂ films was conducted on Si substrates at 900°C using a single-source unimolecular precursor Zr(BH₄)₄ in a molecular beam epitaxy chamber. Epitaxial growth of ZrB₂(0001) was accomplished despite the very large lattice mismatch between ZrB₂ and Si(111). High-resolution cross-sectional transmission electron microscopy images of the sharp ZrB₂/Si interface revealed a heteroepitaxial relationship involving a “magic mismatch” of coincidence lattices. The GaN films grown on the ZrB₂ /Si template was virtually homoepitaxy because of the very small lattice mismatch, 0.6%, between the in-plane lattice parameters of ZrB₂(0001) and GaN(0001). The properties of ZrB₂ thin films deposited on silicon make it an ideal template for the incorporation of group III nitrides with current silicon-based technologies.