Investigating 4H-SiC epilayer thickness variation in high-resolution Ni/Y₂O₃/4H-SiC MOS detectors

Abstract This study investigates the performance of Ni/Y₂O₃/4H-SiC metal–oxide–semiconductor (MOS) radiation detectors fabricated on 4H-SiC epilayers of 50, 150, and 250 µm thicknesses. The impact of epilayer thickness on electrical behavior, defect dynamics, and alpha particle response in Y₂O₃-gated 4H-SiC detectors is systematically examined. Leveraging the wide bandgap of 4H-SiC and the high dielectric constant and thermal stability of Y₂O₃, the devices are optimized for high-resolution radiation detection in harsh environments. A 40 nm Y₂O₃ dielectric layer, deposited via pulsed laser deposition, retained the Schottky-like behavior and efficient charge transport of the detectors. Device characterization included current–voltage and capacitance–voltage measurements to assess Schottky barrier properties, deep-level transient spectroscopy to analyze defect states, and alpha pulse height spectroscopy to evaluate detection response. The detector with a 250 µm epilayer exhibited lower leakage current and reduced concentrations and capture cross-sections of Z 1/2 and EH 6/7 traps—defects known to impair charge collection. However, despite these favorable electrical and defect characteristics, the 250 µm device showed a comparatively lower alpha detection response than thinner epilayer detectors. This behavior suggests an influence of the Y₂O₃/4H-SiC interface, particularly in thicker epilayers, where interfacial states or field distortions may hinder carrier transport. Overall, the findings provide new insights into optimizing thick epilayer MOS detector architectures and underscore the importance of interface engineering to advance robust, high-performance 4H-SiC-based radiation detectors for space, nuclear, and high-energy physics applications.