High-resolution x- and γ-ray detection using 4H-SiC n-type epitaxial layer

Abstract

Schottky barrier diode (SBD) radiation detectors on n-type 4H-SiC epitaxial layer have been fabricated and evaluated for low energy x- and γ-rays detection. The detectors were highly sensitive to soft x-rays in the 50 eV to few keV range and showed 2.1% resolution in detecting low energy y-rays of 59.6 keV from 241Am x/γ ray source. The detector's response to soft x-rays was significantly higher than that of commercial off-the-shelf (COTS) SiC UV photodiode. The devices have been characterized by current-voltage (I-V) measurements in the 94-700 K range, thermally stimulated current (TSC) spectroscopy, x-ray diffraction (XRD) rocking curve measurements, and defect delineating chemical etching. I-V characteristics of the detectors at 500 K showed low leakage current (<; 2 nA at 200 V) revealing a possibility of high temperature operation. XRD rocking curve measurements revealed high quality of the epitaxial layer exhibiting full width at half maximum (FWHM) of the rocking curve - 3.6 arc sec. TSC studies in wide temperature range of 94 - 550 K revealed relatively shallow levels (0.25 eV) in the epi bulk with the density ~7×1013 cm-3 related to AI and B impurities and deeper levels located near the metal-semiconductor interface only. Our measurements showed no effect of charge trapping on detector's responsivity in the low energy x-ray range.