Papers by Author: Toshihiko Hayashi

Abstract: Thermal anisotropy in 4H-, and 6H-SiC bulk single crystal wafers was studied by the PPE method. The thermal diffusivities of the [1-100] and [11-20] orientations (^c-axis) samples were higher than those of the [0001] orientation (//c-axis) samples. Moreover, the thermal anisotropies of the lattice component and the carrier component were analyzed by Raman measurement.

Abstract: The advantage of room-temperature photoluminescence (PL) mapping was demonstrated for nondestructive detection of stacking faults (SFs) in off-oriented 4H-SiC epitaxial and bulk wafers. In mapping of the SF-related emission at 2.9 eV on the wafers, the SFs in the surface region appeared as a bar-shaped pattern with the long side perpendicular to the off-cut direction. The use of 266 nm light excitation is essential to detect the SF pattern in the bulk wafers because of its shallow penetration depth. The dark lines crossing the bar-shaped patterns in the epitaxial wafers are ascribable to the basal plane dislocation located close to the SF-planes.

Abstract: The effectiveness of room-temperature photoluminescence (PL) mapping was demonstrated for nondestructive detection of structural defects, such as dislocations, micropipes and stacking faults, in SiC wafers. PL spectra of bulk wafers were dominated by deep-level emissions due to Si vacancies, vanadium and undefined centers like UD-1 at room temperature, while those from epitaxial wafers involved near band-edge emission. We developed a whole-wafer PL intensity mapping system with a capability of zooming in on the area of interest with a spatial resolution as high as 1 μm, and showed that the mapping patterns agree well with the etch-pit patterns originating from the structural defects both on a wafer scale and on a microscopic scale. The intensity contrast around the defects varied depending on the emission band, suggesting differences in their interactions with impurities and point defects.

Abstract: Growth of 4H-SiC bulk crystals on 4H-SiC {03-38} seeds was done. 4H-SiC {03-38} is obtained by inclining the c-plane toward <01-10> at a 54.7 degrees angle. Growth on the 4H-SiC {03-38} seed has the potential to achieve high quality crystals without micropipes and stacking faults. Micropipe-free c-plane 4H-SiC wafers were achieved by growth on the 4H-SiC {03-38} seed. A transmission X-ray topograph image of the micropipe free c-plane wafer revealed that there are no macroscopic defects with displacements.