Influence of defect traps and inhomogeneities of SiC crystals and radiation detectors on carrier transport

We present investigation of carrier traps and their transport in 4H-SiC single crystals and high energy radiation detectors. SiC detectors have been produced from bulk vanadium-compensated semi-insulating 4H-SiC single crystal. They were sup-plied with a nickel ohmic contact on the back surface and titanium Schottky contact on the front surface. The prevailing de-fect levels were revealed by means of thermally stimulated current (TSC) and thermally stimulated depolarization (TSD) methods and their advanced modification multiple heating technique. From I-V measurements of the samples a barrier height of ~ 1.9 eV was found. In 4H-SiC:Va, the following thermal activa-tion values were deduced: 0.180.19 eV, 0.200.22 eV, 0.330.41 eV, and 0.63 eV. The maximum with activation energy of 0.330.41 eV appears below 125 K and most probably is caused by the thermal carrier generation from defect levels. In con-trast, the first two maxima with the lowest activation energies, which nevertheless appear at higher temperatures, are likely associated with material inhomogeneities causing potential fluctuations of the band gap. The existence of different polariza-tion sources in different temperature ranges is also demonstrated by TSD