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The epitaxial growth of 4H-SiC on on-axis substrates is a very important process to meliorate in order to accelerate the development and improve the performance of bipolar SiC-based power devices, but until now, only relatively low growth rate processes have been achieved. The aim of this study is to demonstrate a high growth rate deposition process of high-quality 4H-SiC epilayers on on-axis substrates, free of 3C-SiC inclusions. Previous studies showed that silicon-rich gas-phase conditions, high Cl/Si ratios, or both were vital in order to avoid 3C-SiC inclusions in the epitaxial layers when grown on on-axis substrates. This study combines the knowledge of surface pretreatment with the chloride-based chemistry developed for off-axis growth. Two different precursor approaches were used, one adopting silane and ethylene with addition of hydrogen chloride and the other based on methyltrichlorosilane (MTS). In this study, we show that using a MTS-based chemical vapor deposition (CVD) process in combination with proper in situ silane etching and accurate optimization of the other process parameters results in homoepitaxial growth of high-purity and high-quality 4H-SiC layers on on-axis Si-face substrates at a growth rate of 100 μm/h. A higher efficiency of the MTS precursor chemistry was found and discussed.

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After low-energy electron irradiation of epitaxial n-type 4H-SiC with a dose of 5 Â 10 16 cm À2 , the bistable M-center, previously reported in high-energy proton implanted 4H-SiC, is detected in the deep level transient spectroscopy (DLTS) spectrum. The annealing behavior of the M-center is confirmed, and an enhanced recombination process is suggested. The annihilation process is coincidental with the evolvement of the bistable EB-centers in the low temperature range of the DLTS spectrum. The annealing energy of the M-center is similar to the generation energy of the EB-centers, thus partial transformation of the M-center to the EB-centers is suggested. The EB-centers completely disappeared after annealing temperatures higher than 700 C without the formation of new defects in the observed DLTS scanning range. The threshold energy for moving Si atom in SiC is higher than the applied irradiation energy, and the annihilation temperatures are relatively low, therefore the M-center, EH1 and EH3, as well as the EB-centers are attributed to defects related to the C atom in SiC, most probably to carbon interstitials and their complexes.

a b s t r a c tA systematic p-type doping study has been performed on 4H-and 6H-silicon carbide (SiC) epilayers grown at high growth rate using chloride-based chemical vapor deposition. The effect of temperature, pressure, growth rate, C/Si-, Cl/Si-ratios and dopant flow on the incorporation of the acceptor atoms aluminum and boron has been studied. The C/Si-ratio on the aluminum incorporation has similar behavior to what has been reported for the standard non-chlorinated low growth rate process, while no clear effect of C/Si-ratio was observed for the boron incorporation. A higher Cl/Si-ratio seems to lead to lower the aluminum and boron incorporation either due to more effective silicon supply at high Cl/Siratio or due to removal of dopant atoms from the surface by chlorine. The doping concentration is stable to the variations in silicon molar fraction, growth pressure and growth temperature for the aluminumdoped layers. Also p-type doping with gallium was tested.