Charge-Trapping Memory Characteristics and Stability Testing of Gd2O3-Based MOS Capacitors

Ag/Gd2O3/Si metal-oxide-semiconductor (MOS) capacitors incorporating RF-magnetron-sputtered Gd2O3 dielectric layers were fabricated to investigate the influence of dielectric thickness on their structural, optical, interfacial, and electrical properties. Films deposited for 2 and 4 h produced Gd2O3 layers of 16.57 and 33.46 nm, respectively. Increasing deposition time promoted partial structural ordering and increased surface roughness, while the optical bandgap decreased slightly from 5.1 to 5.0 eV. The thicker film’s greater roughness correlated with a higher interface-state density (∼1.02 × 1011 eV–1 cm–2) compared with the thinner film (9.07 × 1010 eV–1 cm–2). Frequency-dependent C–V and G–V measurements revealed clear deep-depletion, depletion, and accumulation regions for both devices; oxide thickness strongly influenced accumulation capacitance, series resistance, and interface behavior. Clockwise C–V hysteresis in both capacitors indicates electron trapping in the Gd2O3 layer. As the sweep voltage increased from ±1 to ±5 V, the memory window widened from 0.66 to 3.05 V for the thinner film and from 1.62 to 3.51 V for the thicker film. The thicker dielectric also had better charge retention, with an extrapolated charge loss of only 3.92% compared to 6.06% for the thinner film. These findings show that tuning Gd2O3 thickness via deposition time is an effective way to optimize interface properties and improve the memory performance of high-k MOS capacitors for future nonvolatile memory applications.