A sophisticated simulation model is developed based on the principle of ray-tracing to simulate the grazing-incidence synchrotron X-ray topographic contrast of dislocations lying on the basal plane including basal plane dislocations and deflected threading screw and mixed dislocations in off-axis 4H-SiC crystals. The model incorporates effects of surface relaxation as well as the photoelectric absorption to predict dislocation contrast. Compared to conventional ray-tracing images, surface relaxation effects dominate dislocation contrast for diffraction near the crystal surface. The simulated dislocation contrast gradually weakens with increasing depth of the diffracted beam position within the crystal due to photoelectric absorption. The distinctive features of the net simulated dislocation images obtained by aggregating through the effective penetration depth correlate well with contrast features observed on the experimental topographic images. Depth analysis reveals that in some cases the diffracted X-rays from regions below the dislocation can contribute additional contrast features previously not considered.

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A multi-energy implantation system has been developed for deep implantation of dopant atoms (Al, B, N, P) in 4H-SiC wafers to fabricate deep junctions for medium and high voltage devices. Energies used range from 13MeV to 66MeV, far higher than those used in conventional implantations. Therefore, lattice damage induced by the implantation process and the recovery by annealing must be characterized in detail for understanding the nature of damage, extent of recovery and its possible effect on device properties. To this end, 4H-SiC wafers with 12 um epilayer were implanted by 13.8 MeV to 65.7 MeV Al and N ions using the multienergy implantation system. Samples were implanted in the form of alternative Al and N pillars or blanket co-implanted with Al and N. The nature of strains induced by the implantation process in asimplanted and post-annealed samples were investigated using Synchrotron X-ray Rocking Curve Topography (SXRCT) and Reciprocal Space Map (RSM). As-implanted samples are characterized by tensile strains. By comparing samples implanted with different fluences, we have confirmed that implantation with higher total fluence introduces higher levels of strains in the 4H-SiC epilayer.

The study of defects and strain in GaN substrates and epilayers for vertical device development using synchrotron X-ray topography techniques is presented. Synchrotron monochromatic beam X-ray topography (SMBXT) studies show that ammonothermal-grown GaN substrate wafers have the lowest dislocation densities while patterned hydride vapor phase epitaxy (HVPE) GaN reveal a starkly heterogeneous distribution of dislocations with large areas containing low threading dislocation densities and HVPE GaN substrates contain high dislocation densities. Epitaxial growth does not nucleate new defects but interactions of dislocations with point defects can cause changes in dislocation configurations. Rocking curve Analysis by Dynamical Simulation (RADS) is shown to be effective in analysis of implantation by correlating the depth profile of strain with the doping profile. Removal of lattice damage induced by implantation requires annealing with proper capping or under high pressures to limit loss of material and lattice distortion. Inductively coupled plasma (ICP) etching may introduce strain in GaN material that can be partially recovered by TBCl etching. Diffusion doping does not introduce new strains in GaN material while neutron transmutation doping at low levels can lead to curing of defects while higher levels lead to irradiation damage and nucleation of new defects.