Determination of frequency and voltage dependence of electrical properties of Al/(Er2O3/SiO2/n-Si)/Al MOS capacitor

In this study, we investigated the effects of applied voltage and frequencies on the electrical properties of Al/(Er2O3(150 nm)/SiO2(20 nm)/n-Si)/Al MOS capacitor. The e-beam deposited Er2O3/SiO2 films were annealed at 650 degrees C in N-2 ambient and the crystal and phase identification of the films were confirmed by X-ray diffractometry. The capacitance-voltage (C-V) and the conductance-voltage (G/omega-V) measurements of the MOS capacitor were carried out for voltage frequencies from 50 kHz to 1 MHz at several steps. The parameters of doping concentration, diffusion potential, built-in potential, barrier height, Fermi energy level, the image force barrier lowering and the depletion layer width were calculated by C-V and G/omega-V data. While the depletion layer width decreased with increasing frequencies, the diffusion potential and the barrier height increased a little with small frequencies (200 kHz <= f) first, then decreased insignificantly. We also studied the frequency effects on the series resistance (R-s) and the interface state density (D-it) through the C-V and G/omega-V curves, and found noticeable decreases in R-s and D-it values with increasing frequency. The measured and calculated results reveal that both R-s and D-it frequency dependence have significant impacts on Er2O3/SiO2/n-Si MOS capacitor properties. These effects are basically because of the interfacial charge behavior of thin SiO2 layer contained in between n-Si and Er2O3.