Alpha Particle Detection Using Highly Rectifying Ni/Ga₂O₃H/4H-SiC Heteroepitaxial MOS Junction

We demonstrate for the first time heteroepi-taxial 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-Ga(2)O(3 )on high-quality detector-grade 4H-SiC epitaxial layers followed by the deposition of Ni gate contacts. The heterojunction devices with beta-Ga(2)O(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 thick-ness; however, the energy resolution did not show any such trend. Capacitance-mode deep-level transient spec-troscopy (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(1/2)) in the 4H-SiC layer did not vary noticeably, the VO 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, y-/X-rays, and neutrons.