Assessment of 4H-SiC Epitaxial Layers and High Resistivity Bulk Crystals for Radiation Detectors

We present results of structural, electrical, and defect characterization of 4H-SiC epitaxial layers and bulk crystals and show performance of the radiation detectors fabricated from these materials. The crystal quality was evaluated by x-ray diffraction (XRD) rocking curve measurements, electron beam induced current (EBIC) imaging, and defect delineating etching in conjunction with optical microscopy and scanning electron microscopy (SEM). Studies of the electrically active intrinsic defects and impurities were conducted using thermally stimulated current (TSC) measurements in a wide temperature range of 94 - 750K. The results are correlated with the capability of bulk crystals and epitaxial layers for the detection of α-particles, low to high energy x-rays and gamma rays. High barrier rectifying Schottky diodes have been fabricated and tested. The epitaxial 4H-SiC radiation detectors exhibited low leakage current (< 1 nA) at ~ 200 V operating voltage up to 200 C. The soft x-ray responsivity measurements performed at the National Synchrotron Light Source (NSLS) at Brookhaven National Lab (BNL) showed significantly improved characteristics compared to commercially-available SiC UV photodiode detectors.