Surface C/Si ratio was demonstrated as a useful indicator for the control of in-wafer distribution of thickness and carrier concentration in 4H-SiC homo-epitaxial films on large-diameter wafers. Close investigation of the dependence of growth rate and carrier concentration on the radial distance from the center of the 150 mm wafer revealed that the actual C/Si ratio just above the wafer: surface C/Si ratio, is quite different to the introduced C/Si ratio. In-wafer distribution of thickness and carrier concentration in the epitaxial films can be explained by the surface C/Si ratio, which suggests that the surface C/Si ratio could be a useful indicator for the precise control of uniform growth on large-diameter wafers. It is also found that two types of SiC films, one with extremely low defect density and the other with low pit density, both with highly uniform growth rate and carrier concentration, could be grown by controlling of the surface C/Si ratio on the whole wafers.
An ex situ AlN seed layer was formed by physical vapor deposition (PVD) on a Si substrate, aiming at the production of high-quality GaN on Si by metal–organic vapor-phase epitaxy. A low density of initial GaN islands were obtained by reducing the trimethylgallium (TMGa) flow rate. The dislocation density of GaN was dramatically reduced with 3D growth compared with 2D growth, as indicated by measurements of XRD rocking curves (FWHM of 384 and 461 arcsec for 0002 and
diffractions, respectively) and cathodoluminescence (CL) mapping (dark-spot density of 3.4 × 108 cm−2) for 1-µm-thick crack-free GaN on a Si substrate. The values were almost equivalent to those of the layers grown on sapphire substrates.
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