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Bulk single crystals of SiC can be grown by a sublimation method, and large-area 6H-SiC and 4H-SiC single crystals are obtained. The occurrence of SiC polytypes is affected by the growth condition, and can be controlled successfully by optimizing these conditions. 6H-SiC is grown on 6H-SiC (0001) Si-faces, and 4H-SiC on 6H-SiC (0001) C-faces. The crystallinity of bulk crystals is investigated by reflection high-energy electron diffraction (RHEED) and X-ray analysis, and characterization is carried out in detail by optical and electrical measurement.
Successful homoepitaxial vapor phase growth of SiC can be realized using off-axis (0001) substrates prepared by a sublimation method called “step-controlled epitaxy”. Since the crystallinity of epilayers is improved during the step-controlled epitaxy, this growth technique is a key for getting high-quality crystal surfaces. Impurity doping is controlled during homoepitaxial growth by employing impurity gases, such as N2, trimethylaluminum (TMA), and B2H6. A wide-range of carrier concentrations of 5 × 1013~3 × 1018 cm?3 for n-type and 5 × 1016~3 × 1020 cm?3 for p-type are realized. The impurity-incorporation mechanism in the step-controlled epitaxy is discussed based on the C/Si ratio dependence of impurity doping.
Electrical properties of SiC grown by step-controlled epitaxy are determined precisely. A high electron mobility of 720 cm2/Vs is obtained in an undoped 4H-SiC epilayer with an electron concentration of 2.5 × 10l6 cm?3 at 300 K. This electron mobility is about two times higher than that of 6H-Sic (~380 cm2/Vs). High breakdown fields of 1~5 × 106 V/cm are obtained for both 6H- and 4H-SiC, one order of magnitude higher than those for Si. A high saturation electron drift velocity of 1.6 × 107 cm/s is obtained in 4H-Sic, which may make possible high performance of high-frequency 4H-SiC power devices. Impurity levels and deep levels are investigated by Hall effect, admittance spectroscopy, and DLTS measurement. Metal/4H-SiC Schottky barrier heights are characterized and a strong dependence on metal work function without strong “pinning” is elucidated.
Device processes are described for ion implantation. Interface properties of SiO2/SiC are characterized in detail using metal-oxide-semicond. 相似文献