High-resolution radiation detection using Ni/SiO2/n-4H-SiC vertical metal-oxide-semiconductor capacitor

In this article, we demonstrate the radiation detection performance of vertical metal-oxide-semiconductor (MOS) capacitors fabricated on 20 mu m thick n-4H-SiC epitaxial layers with the highest energy resolution ever reported. The 100 nm SiO2 layer was achieved on the Si face of n-4H-SiC epilayers using dry oxidation in air. The Ni/SiO2/n-4H-SiC MOS detectors not only demonstrated an excellent energy resolution of 0.42% (Delta E/E x 100) for 5.48 MeV alpha particles but also caused a lower enhancement in the electronic noise components of the spectrometer compared with that observed for the best high-resolution Schottky barrier detectors. The MOS detectors also exhibited a high charge collection efficiency (CCE) of 96% at the optimized operating bias despite the presence of the oxide layer. A drift-diffusion model applied to the CCE vs gate bias voltage data revealed a minority (hole) carrier diffusion length of 24 mu m. Capacitance mode deep level transient spectroscopy (C-DLTS) scans in the temperature range 84-800 K were carried out to identify the resolution limiting electrically active defects. Interestingly, the C-DLTS spectra revealed both positive and negative peaks, indicating the simultaneous presence of electron (majority) and hole (minority) trap centers. It has been inferred that at the steady-state bias for the C-DLTS measurement, the MOS detector operates in the inversion mode at certain device temperatures, causing holes to populate the minority trap centers and, hence, manifests minority carrier peaks as well. Published under an exclusive license by AIP Publishing.

Automated summary

This article demonstrates the radiation detection performance of vertical metal-oxide-semiconductor (MOS) capacitors fabricated on n-4H-SiC epitaxial layers, achieving the highest energy resolution reported. The MOS detectors showed excellent energy resolution for alpha particles and lower enhancement in electronic noise compared to Schottky barrier detectors. Published under an exclusive license by AIP Publishing.