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We report on the growth and crystal quality of CVD epitaxial layers grown on porous SiC (PSC) substrates. A layer of porous SiC was fabricated by surface anodization of commercial 4H and 6H-SiC (0001)Si face off-axis wafers. The 4H and 6H-SiC epilayers were grown on porous SiC (PSC) substrates using atmospheric pressure CVD at 1580°C and a Si to C ratio of 0.3. Results of X-ray diffraction, RHEED, SEM and AFM characterization demonstrated good surface quality of the films grown on porous material. PL data indicate a greatly improved defect structure in the epi layers grown on PSC as compared to control samples. Preliminary etch pit experiments to estimate the dislocation density indicate a three-fold reduction in defect density in the epi material grown on PSC substrates as compared to epi grown conventional substrates.

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The results of the initial experiments with halogenated carbon precursor chloromethane (CH3Cl) for epitaxial growth of 4H-SiC are presented. The growth rate for mirror-like morphology was easily increased up to about 7 µm/hr at C-rich conditions without detectable surface morphology degradation. Further increase of the silane flow resulted in island formation. The growth with the traditional silane-propane system at the same conditions (and optimized Si/C ratio) produced a very different result, with the growth rate decreasing from upstream to downstream, and morphology degradation taking place for much lower growth rate than in CH3Cl growth. Consequently, the epitaxial growth with chloromethane appears to have significantly different kinetics of the gas-phase precursor decomposition and different mechanisms of the surface reactions, which favors the step-flow growth. In addition, these preliminary data indicated that the maximum achievable growth rate corresponding to the good surface morphology may be noticeably larger for the CH3Cl+SiH4+H2 growth system.

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