Effect of Enhanced Hole Transport on the Performance of Ni/Y2O3/n-4H-SiC Epilayer Radiation Detectors

A significant enhancement in the electrical and charge transport properties has been achieved in self-biased Ni/Y2O3/n-4H-SiC (NiYOSiC) epitaxial layer-based metal–oxide–semiconductor (MOS) radiation detectors compared to conventional Schottky barrier detectors (SBDs). Y2O3 epitaxial layers with thickness ranging from 10 to 120 nm have been deposited on the n-type 4H-SiC epitaxial layer using pulsed laser deposition (PLD) followed by the deposition of Ni gate. The MOS detectors showed excellent rectification behavior with high barrier height and leakage current densities (< 0.06 nA/cm2 at −500 V) lower by an order of magnitude compared to the benchmark Ni/4H-SiC SBDs. The MOS detectors also demonstrated a near 100% charge collection efficiency (CCE) at a much lower electric field compared to SBDs, which was found to be due to the improved hole diffusion length. Extraordinarily longer hole diffusion lengths have been calculated using a drift-diffusion model and alpha particle spectrometry. Energy resolution as high as 0.4% [22-keV full-width at half-maximum (FWHM)] for 5486-keV alpha particles has been observed at optimized operating conditions. The self-biased energy resolution of 1.5% was also found to be substantially higher than that observed in SBDs. While the optimum detector performance has been found to be limited by the presence of <inline-formula> <tex-math notation="LaTeX">${Z} _{1/2}$ </tex-math></inline-formula> and EH6/7 trap levels in the 4H-SiC epilayer, the unprecedented self-biased performance has been achieved for the first time due to the introduction of passivating Y2O3 epitaxial layers. The observed performance of the novel NiYOSiC MOS detectors demonstrated their prospect as radiovoltaics, UV photovoltaics, and self-biased radiation detectors for space missions and advanced nuclear reactors.