Alloys and compound in the C-Si-Ge-Sn system
 
A summary of recent work on synthesis of semiconductor alloys and compounds in the C-Si-Ge system involving epitaxial heterostructures and nanostructures which are intended for Si-based bandgap engineering and lattice matching will be presented. These materials are created heteroepitaxially on Si and include diamond cubic alloys and strain stabilized ordered phases in the C-Si-Ge-Sn system. Examples of new compound semiconductors include the Si₄C,Ge₄C,and (Si₂Ge)C_x compositions with diamond-cubic structures and the Si₃GeC₄ phase with a sphalerite-like structure. Random alloy systems include silicon-germanium-carbon solid solutions, monocrystalline and nanostructured (quantum dots and wires) Ge_1-xC_x hybrids of Ge and diamond and related Si_1-xC_x materials. Current work aimed towards synthesis of new ternary Si-Sn-C and Ge-Sn highly metastable phases will be highlighted. Perfectly epitaxial diamond-cubic Ge-Sn materials are created on Si (100) and exhibit unprecedented thermal stabilities superior crystallinities and unique crsyallographic and optical properties such as adjustable badngaps and lattice constants. The optical, vibrational and structural properties of these materials will be discussed. The presentation emphasizes an approach that combines novel precursor chemistries and modern deposition techniques (ultrahigh vacuum chemical vapor deposition) to develop thin films of new inorganic materials.

Development of group III nitrides and quaternary compounds in the SiCALN system
 
Growth and optical properties of epitaxial nitrides and related carbide nitride hybrids via novel chemical routes is presented. The first part of the presentation is focused on growth and characterization of GaN heterostructures and nanostructures on Si via low-temperature MBE/CVD methods utilizing new families of single source inorganic precursors of composition H₂GaN₃, D₂GaN₃ and H(Cl)GaN₃. This approach represents one of the simplest possible and most versatile synthetic routes to GaN.
The second part deals with epitaxial growth of metastable SiCAlN solid solutions on SiC and Si via reactions between a unimolecular source SiH₃CN and Al atoms. High hardness single phase SiCAlN that luminescences at 3.2 eV and displays an ordered hexagonal 2H/2H and 4H/2H structure is grown on 6H SiC at 750 °C. Commensurate heteroepitaxy of SiCAlN on Si (111) is facilitated by in situ formation of crysstalline oxide interfaces based on the Al-Si-O-N system. Integration of widebandgap semiconductors with Si is readily achieved by this method.