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 y-rays detection. The detectors were highly sensitive to soft x-rays in the 50 eV to few keY range and showed 2.1 % resolution in detecting low energy y-rays of 59.6 keY from 24 1 Am x/y 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 -7xlO 1 3 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.

Wide-Bandgap Semiconductors for Radiation Detection: A Review

“…Using the various alpha emitters such as 148 Gd, 238 Pu, 225 Ac, 221 Fr, 217 At, and 213 Po in the 3.18–8.38 MeV energy range, an excellent energy resolution was achieved. Through the years, progress in energy resolution and efficiency has been reported by many authors [ 29 , 30 , 31 , 32 ]. Chaudhuri et al [ 32 ] achieved an excellent energy resolution of 0.29% at the full width at half maximum (FWHM) for 5.48 MeV alpha particles using a 20 µm thick 4H-SiC epitaxial layer.…”