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Silicon carbide (SiC) is the only wide-bandgap semiconductor to possess native oxide layer thus favoring efficient fabrication of metal-oxide-semiconductor (MOS) devices. 4H-SiC MOS structure has recently been demonstrated as improved radiation detector compared to the conventional Schottky barrier architecture. We report the fabrication of vertical Au/SiO2/n-4H-SiC MOS capacitors for radiation detection, by dry-oxidation of 20 μm thick n-type 4H-SiC epitaxial layer in air at 1000°C. Charge-carrier traps (defects) are known to limit the performance of semiconductor devices. In order to characterize the defects, capacitance mode deep level transient spectroscopy (C-DLTS) was carried out. Apart from regular electron-traps e.g., Ti-impurity and Z1/2 sites, we have also observed the carbon-interstitial related hole traps HK3. While studying defect centers in these devices using a filling pulse peaking to 0 V from a quiescent reverse gate voltage VG = -4 V, we observed a robust positive peak centered around 650 K. Positive peaks in C-DLTS scan indicates minority-carrier trapping, although above-mentioned type of filling pulses does not populate minority-carrier trap centers normally. The activation energy of the observed trap, most likely a carbon vacancy (HK3), was calculated to be 1.27 eV above the valence band edge.
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