RESUMO
The transport mechanism of HfO2-based metal-ferroelectric-metal (MFM) capacitors was investigated using low-frequency noise (LFN) measurements for the first time. The current-voltage measurement results revealed that the leakage behavior of the fabricated MFM capacitor was caused by the trap-related Poole-Frenkel transport mechanism, which was confirmed by the LFN measurements. The current noise power spectral densities (SI) obtained from the LFN measurements followed 1/f noise shapes and exhibited a constant electric field (E) × SI/I2 noise behavior. No polarization dependency was observed in the transport characteristics of the MFM capacitor owing to its structural symmetry.
RESUMO
A normally-off ß-Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET) is proposed using a technology computer-aided design (TCAD) device simulation, which employs an epitaxial drift layer grown on an n-type low-doped body layer. The low-doped body layer under the MOS gate enabled normally-off operation, whereas the epitaxial drift layer determined the on-resistance and breakdown characteristics. The effects of the doping concentration of each layer and thickness of the drift channel layer on the device characteristics were investigated to design a device with a breakdown voltage of 1 kV. A threshold voltage of 1.5 V and a breakdown voltage of 1 kV were achieved by an n-type body layer with a doping concentration of 1 × 1015 cm-3 and an n-type drift layer with a doping concentration of 3 × 1017 cm-3, a thickness of 150 nm, and a gate-to-drain distance of 9.5 µm; resulting in an on-resistance of 25 mΩ·cm2.
RESUMO
In this study, we evaluated the temperature- and frequency-dependent ferroelectric characteristics of TiN/undoped HfO2/TiN metal-ferroelectric-metal (MFM) capacitors in which an undoped HfO2 film was deposited through atomic layer deposition (ALD). Successful ferroelectric characteristics were achieved after postdeposition annealing at 650 °C, which exhibited a remanent polarization of 8 µC/cm2 and a coercive electric field of 1.6 MV/cm at 25 °C (room temperature). The ferroelectric property was maintained at 200 °C and decreased as the temperature increased. The ferroelectric property was completely lost above 320 °C and fully recovered after cooling. The frequency dependency was evaluated by bias-dependent capacitance-voltage and s-parameter measurements, which indicated that the ferroelectric property was maintained up to several hundred MHz. This study reveals the ultimate limitations of the application of an undoped HfO2 MFM capacitor.
