Carrier transport in SiC crystals and radiation detectors as affected by defect traps and inhomogeneities

Carrier trapping and transport were investigated in 4H-SiC single crystals and radiation detectors produced from bulk vanadium-compensated semi-insulating 4H-SiC. The defect levels were revealed by means of the Thermally Stimulated Currents in multiple heating mode. The following thermal activation energy values were deduced: 0.18–0.19 eV, 0.20–0.22 eV, 0.33–0.41 eV, and 0.63 eV. The maximum with activation energy of 0.33–0.41 eV appears below 125 K and most probably is caused by the thermal generation from defect levels. In contrast, the first two maxima with lowest activation energies appear at higher temperatures and are likely associated with material inhomogeneities causing potential fluctuations of the band gap. The existence of different polarization sources in different temperature ranges is also demonstrated by Thermally Stimulated Depolarization.