Molecular beam epitaxial growth of AlN on sapphire and 6H-SiC has been performed utilizing mono-energetic activated nitrogen ion beams (2-80 eV kinetic energies). The growth temperature of AlN in MBE is found to be limited by the sticking coefficient of incident reactants. The combination of elevated growth temperatures (1050-1150°C), high kinetic-energy reactive nitrogen (>40 eV) and post-growth thermal processing (1150-1350°C) produces high-quality AlN thin-f ilms with narrow rocking curve widths (<2 arcmin) and low dislocation densities (<∼3×108cm−2). In contrast, the use of in-situ step anneals during synthesis did not achieve similar quality materials.

Planar (001)Si/(0001) Si-terminated 6H-SiC interfaces were synthesized by UHV diffusion bonding of cleaned, on-axis and vicinal wafers at 1100°C for 5 hours, at MPa pressure. The interfaces were crystalline up to their defining plane, without nanospectroscopically detectable impurities. The crack opening tests showed the interfaces were stronger than the Si substrates. Oxygen on the substrate surfaces resulted in silicon carbide on insulator (SiCOI) interface formation.

Biaxially aligned film growth by dual-ion-beam sputtering method were studied for fluorite type (Zr0.85Y0.15O1.93(YSZ), Hf0.74Yb0.26O1.87, CeO2), pyrochlore type (Zr2Sm2O7), and rare-earth C type (Y2O3, Sm2O3) oxides on polycrystalline Ni-based alloy substrates. Cube-textured (all axes aligned with a <100> axis substrate normal) films were obtained for fluorite and pyrochlore ones by low energy (<300 eV) ion bombardment at low temperatures (< 300 °C). Besides, cube textured Y2O3 films were obtained in far narrow conditions with a quite low energy (150 eV)-ion bombardment at the temperature of 300°C. The assisting ion energy dependence was discussed in connection with lattice energies for these oxide crystals.

The residual stress and the microstructure associated with it were studied in connection with the Pd-Ge ohmic contact formation on GaAs. Evaporated Pd (20 nm) / Ge (150 nm) / Pd (50 nm) thin film stacks on GaAs were annealed at various temperatures and the resulting microstructures were investigated by transmission electron microscopy (TEM). Micro-cantilever beam structures were fabricated with a focused ion beam (FIB) workstation and the residual stress present was calculated from the deflection magnitude. It was found that Ge solid phase epitaxial (SPE) growth on GaAs is associated with a stress relaxation of the thin film system. A new model that suggests the tensile stress induced by the intermediate layer may play an important role in the SPE growth mechanism is proposed. Other cases of solid phase heteroepitaxial growth with an intermediate medium, such as Ge/Au/Si, Co/Ti/Si (the TIME method) and Co/SiOx/Si (the OME method) are discussed in light of this newly proposed model. Also, the possibility of using controlled stress to engineer new methods for growing SPE based heterostructures will be presented.

MBE growth of ZnO films for optical semiconductor devices was investigated on off-angled c-plane sapphire substrates. Twin crystal RHEED patterns and surface facetting observed with c-plane just-oriented substrates were suppressed by enlarging the offset angles from near-zero to 2.87 degrees. Though no significant changes were seen in optical characteristics, FWHM of XRC narrowed and surface morphology improved with larger offset angles, indicating that the offset angle is also a sensitive factor for ZnO film growth.

Electrical conduction and magnetic behavior of ferromagnetic SrRuO3 (bulk Tc= 160 K) were tuned systematically using the structural transitions of ferroelectric BaTiO3 as the growth template. Abrupt resistivity changes of SrRuO3 were observed at the structural transition temperatures of the BaTiO3substrate. The observed effect appears to originate from the lattice changes of BaTiO3 (cubic to tetragonal at 393K, tetragonal to orthorhombic at 278K, and orthorhombic to rhombohedral at 183K) induced by an expansion of spontaneous polarization axis. The observed phenomenon will be very useful for the fabrication of novel perovskite oxide devices.

The main unsolved problem in SiC technology is a high density of defects in substrate materials (micropipes and dislocations) propagating into device structures and causing device failure. Recently, significant progress in defect density reduction in semiconductor materials has been achieved using epitaxial lateral overgrowth techniques. In this paper, we describe a novel technique, which shows a high potential for defect reduction in epitaxial and bulk SiC. This technique is based on nano-scale epitaxial lateral overgrowth (NELOG) method, which employs porous substrate materials. Usually, the pores are from 50 to 500 nm in size and epitaxial material overgrowing these pores, forms continues high-quality layer. It is important that the NELOG method does not require any mask. This technique may be easily scaled for large area substrates.

In this work, SiC layers were grown on porous SiC by sublimation method, which is widely used for both epitaxial and bulk SiC growth. Porous SiC substrates were formed by surface anodization of SiC commercial wafers. It was shown that SiC layers grown on porous SiC substrates have smooth surface and high crystal quality. The surface of overgrown material was uniform and flat without any traces of porous structure. X-ray topography indicated significant defect density and stress reduction in SiC grown on porous material. Photoluminescence measurements showed a reduction of deep level recombination in SiC.

Strain relaxed graded SiGe buffer layers have been grown by low energy plasma enhanced chemical vapour deposition (LEPECVD). Due to the low ion energies involved in LEPECVD, exceptionally high plasma intensities can be applied without any ion damage of the epitaxial layers. Transmission electron microscopy and X-ray reciprocal space mapping show that relaxed buffer layers grown at rates exceeding 5 nm/s are of a comparable quality to buffer layers grown by standard techniques at much lower rates. Low temperature electric transport measurements on remotely doped tensilely strained Si quantum wells synthesized by LEPECVD show that also good electrical quality is achieved.