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

We demonstrate for the first time heteroepitaxial metal-oxide–semiconductor (MOS) structures as radiation detectors for harsh environment applications. The Ni/ $\beta $ -Ga2O3/4H-SiC MOS structure has been achieved by metal-organic chemical vapor deposition (MOCVD) of $\beta $ -Ga2O3 on high-quality detector-grade 4H-SiC epitaxial layers followed by the deposition of Ni gate contacts. The heterojunction devices with $\beta $ -Ga2O3 epitaxial layers in the thickness range 50–500 nm deposited on 20- $\mu \text{m}$ -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 ( ${Z}_{\text {1/2}}$ ) in the 4H-SiC layer did not vary noticeably, the ${V}_{\text {O}}$ 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 $ -Ga2O3/4H-SiC MOS devices showed excellent radiation response, and due to the ultrawide bandgap of $\beta $ -Ga2O3, 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.