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 Y
₂
O
₃
film on n-type GaN substrate were studied. As-deposited Y
₂
O
₃
film was amorphous as no Y
₂
O
₃
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-Ga
₂
O
₃
phase for samples annealed beyond 400°C denoted the formation of interfacial layer (IL) consisting of an Y
₂
O
₃
and β-Ga
₂
O
₃
mixture. The formation of IL was revealed by cross-sectional energy-filtered transmission electron microscopy images. Metal-oxide-semiconductor characteristics of Y
₂
O
₃
/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.