Alpha Particle Detection Using Highly Rectifying Ni/Ga 2 O 3 /4H-SiC Heteroepitaxial MOS Junction

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Abstract
We demonstrate for the first time heteroepitaxial metal–oxide–semiconductor (MOS) structures as radiation detectors for harsh environment applications. The Ni/ $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ /4H-SiC MOS structure has been achieved by metal–organic chemical vapor deposition (MOCVD) of $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ on high-quality detector-grade 4H-SiC epitaxial layers followed by the deposition of Ni gate contacts. The heterojunction devices with $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ epitaxial layers in the thickness range 50–500 nm deposited on 20- $\mu $ m-thick 4H-SiC epilayers have shown excellent rectification with barrier height up to 1.5 eV without any thermal annealing. The charge collection efficiency (CCE) of the detectors in pulse-height detection mode decreased systematically with an increase in the oxide layer thickness; however, the energy resolution did not show any such trend. Capacitance-mode deep-level transient spectroscopy (C-DLTS) measurements showed the presence of a defect level situated 1.2 eV below the conduction band minimum (CBM) of 4H-SiC identified as ON1 center. While the concentration of the potential trap center ( $\textit{Z}_{\text{1/2}}$ ) in the 4H-SiC layer did not vary noticeably, the $\textit{V}_{\text{O}}$ center showed strong dynamics with the oxide layer thickness and has been identified as the key defect in defining the ultimate detector resolution. Overall, the novel Ni/ $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ /4H-SiC MOS devices showed excellent radiation response, and due to the ultrawide bandgap of $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ , they are poised to be excellent ultraviolet (UV) detector extended to the deep UV region—a very important addition to its versatility of detecting wide range of radiation, including charge particles, $\gamma $ -/X-rays, and neutrons.
Funding Information
  • National Science Foundation (2124624)
  • DOE Office of Nuclear Energy’s Nuclear Energy University Program (DE-NE0008662)
  • South Carolina National Aeronautics and Space Administration (NASA) Established Program to Stimulate Competitive Research (EPSCoR) Research Grant Program (10011935)
  • SC Space Grant Research and Education Awards Program (10013007)

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