High-purity 6H-SiC single crystals were grown by the halide chemical-vapor deposition process. Growth was performed in a vertical hot-wall reactor with a separate injection of a silicon precursor (silicon tetrachloride) and a carbon precursor (propane). Typical growth rates were between 100 and 300μm∕h. The crystals contain very low concentrations of residual impurities. The main contaminants, namely, nitrogen and boron, are in the 1014atomscm−3 range. Crystals grown under Si-rich conditions were n type with low room temperature electron concentrations in the 1014–1015atomscm3 range and with room-temperature electron mobilities approaching 400cm2∕Vs. The resistivity of the material increased up to 1010Ωcm with increasing C∕Si ratio. Deep levels spectra show that the electron traps density decreases with increasing C∕Si ratio.

A novel halide chemical vapor deposition (HCVD) process has been developed for bulk growth of high purity, single crystal 6H SiC. The effects of major process parameters including furnace temperature over the range of 1900-2150°C, reactor pressure over the range of 20-400 torr, reactant concentrations, and flow rates on the growth rate, crystallinity, and electrical properties of the single-crystal 6H boules grown by HCVD are described. Typical growth rates for the 6H polytype are on the order of 100-125 µm/h with a maximum observed rate of 180 µm/h. Thicknesses up to 1 mm have been demonstrated. GDMS analyses of the purity of HCVD grown material is discussed and compared to 6H SiC produced by commercial PVT and HTCVD processes. Boron and aluminum concentrations less than 1.8 E 15 atoms/cm 3 were demonstrated.

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4H-SiC Schottky rectifiers with dielectric overlap edge termination were exposed to 40 MeV protons at fluences from 5×107–5×109 cm−2. The reverse breakdown voltage decreased from ∼500 V in unirradiated devices to ∼−450 V after the highest proton dose. The reverse leakage current at −250 V was approximately doubled under these conditions. The forward current at −2 V decreased by ∼1% (fluence of 5×107 cm−2) to ∼42% (fluence of 5×109 cm−2), while the current at lower biases was increased due to the introduction of defect centers. The ideality factor, on-state resistance, and forward turn-on voltage showed modest increases for fluences of ⩽5×108 cm−2, but were more strongly affected (increase of 40%–75%) at the highest dose employed.

A variety of defect-sensitive techniques have been employed to detect, identify, and quantify the residual impurities and native defects in high-purity (undoped) 6H-SiC crystals grown by halide chemical-vapor deposition technique. The incorporation efficiencies of N and B are determined by the site-competition effect. Most notably, material with low residual N levels (∼1014cm−3) can be produced. In addition, the nitrogen concentrations obtained from Hall-effect measurements and low-temperature photoluminescence are systematically lower than those determined from secondary-ion-mass spectrometry. The difference is ascribed to nitrogen forming complexes with native defects. The energy level of this complex is approximately 0.27eV below the conduction band. Four major electron traps with activation energies of 0.4, 0.5, 0.65, and 1eV and five hole traps with activation energies of 0.3, 0.4, 0.55, 0.65, and 0.85eV were observed by deep-level transient spectroscopy. The concentration of all traps decreased strongly with increasing C∕Si ratio during growth. Increasing the C∕Si flow ratio also led to increased resistivity of the crystals and change of conductivity from conductive n type to high-resistivity p type. The Fermi level in p-type material is pinned either to highly compensated shallow B acceptors or to deep B-related center at 0.6eV above the valence band. Electron paramagnetic resonance shows the presence of positively charged carbon vacancies in such high-resistivity material.