Study on Gallium Nitride-Based Metal–Oxide–Semiconductor Capacitors With RF Magnetron Sputtered $\hbox {Y}_{2}\hbox {O}_{3}$ Gate

Effects of postdeposition annealing (PDA) temperatures (200°C-1000°C) in argon ambient on radio-frequency magnetron sputtered Y₂O₃ film on n-type GaN substrate were studied. As-deposited Y₂O₃ film was amorphous as no Y₂O₃ phase was detected by X-ray diffraction. A transformation of the amorphous to polycrystalline phase happened when PDA (≥ 200°C) was carried out. The detection of β-Ga₂O₃ phase for samples annealed beyond 400°C denoted the formation of interfacial layer (IL) consisting of an Y₂O₃ and β-Ga₂O₃ mixture. The formation of IL was revealed by cross-sectional energy-filtered transmission electron microscopy images. Metal-oxide-semiconductor characteristics of Y₂O₃/GaN structure annealed at different temperatures were correlated with structural and surface morphology analysis. The 400-°C-annealed sample demonstrated the highest electric breakdown field (~ 10.7 MV/cm) due to the attainment of the lowest effective oxide charge, semiconductor-oxide interface-trap density, and total interface-trap density.