Comprehensive Research of Total Ionizing Dose Effects in GaN-Based MIS-HEMTs Using Extremely Thin Gate Dielectric Layer.

The device performance deterioration mechanism caused by the total ionizing dose effect after the γ-ray irradiation was investigated in GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) for a 5 nm-thick SiN and HfO gate dielectric layer. The γ-ray radiation hardness according to the gate dielectric layer was also compared between the two different GaN-based MIS-HEMTs. Although HfO has exhibited strong tolerance to the total ionizing dose effect in Si-based devices, there is no detail report of the γ-ray radiation effects in GaN-based MIS-HEMTs employing a HfO gate dielectric layer.

Charging Effect by Fluorine-Treatment and Recess Gate for Enhancement-Mode on AlGaN/GaN High Electron Mobility Transistors.

An enhancement-mode AlGaN/GaN metal-insulator-semiconductor high-electron- mobility-transistor was fabricated using a recess gate and CF plasma treatment to investigate its reliable applicability to high-power devices and circuits. The fluorinated-gate device showed hysteresis during the DC current-voltage measurement, and the polarity and magnitude of hysteresis depend on the drain voltage. The hysteresis phenomenon is due to the electron trapping at the AlO/AlGaN interface and charging times longer than milliseconds were obtained by pulse I-V measurement.

Channel Defect Profiling and Passivation for ZnO Thin-Film Transistors.

The electrical characteristics of Zinc oxide (ZnO) thin-film transistors are analyzed to apprehend the effects of oxygen vacancies after vacuum treatment. The energy level of the oxygen vacancies was found to be located near the conduction band of ZnO, which contributed to the increase in drain current (I) via trap-assisted tunneling when the gate voltage (V) is lower than the specific voltage associated with the trap level. The oxygen vacancies were successfully passivated after the annealing of ZnO in oxygen ambient.

Operation Mechanism of a MoS₂/BP Heterojunction FET.

The electrical characteristics and operation mechanism of a molybdenum disulfide/black phosphorus (MoS₂/BP) heterojunction device are investigated herein. Even though this device showed a high on-off ratio of over 1 × 10⁷, with a lower subthreshold swing of ~54 mV/dec and a 1fA level off current, its operating mechanism is closer to a junction field-effect transistor (FET) than a tunneling FET. The off-current of this device is governed by the depletion region in the BP layer, and the band-to-band tunneling current does not contribute to the rapid turn-on and extremely low off-current.

Wafer-Scale Integration of Highly Uniform and Scalable MoS Transistors.

Molybdenum disulfide with atomic-scale flatness has application potential in high-speed and low-power logic devices owing to its scalability and intrinsic high mobility. However, to realize viable technologies based on two-dimensional materials, techniques that enable their large-area growth with high quality and uniformity on wafer cale is a prerequisite. Here, we provide a route toward highly uniform growth of a wafer-scale, four-layered MoS film on a 2 in.

Characteristics of a pressure sensitive touch sensor using a piezoelectric PVDF-TrFE/MoS2 stack.

A new touch sensor device has been demonstrated with molybdenum disulfide (MoS2) field effect transistors stacked with a piezoelectric polymer, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE). The performance of two device stack structures, metal/PVDF-TrFE/MoS2 (MPM) and metal/PVDF-TrFE/Al2O3/MoS2 (MPAM), were compared as a function of the thickness of PVDF-TrFE and Al2O3. The sensitivity of the touch sensor has been improved by two orders of magnitude by reducing the charge scattering and enhancing the passivation effects using a thin Al2O3 interfacial layer.

Ferroelectric polymer-gated graphene memory with high speed conductivity modulation.

The feasibility of a high speed ferroelectric graphene memory device using a ferroelectric polymer (PVDF-TrFE)/graphene stack has been demonstrated. The conductivity of this metal-ferroelectric-graphene (MFG) device could be modulated up to 775% with a very fast programming speed down to 10 ns. Also, programmed states were maintained up to 1000 s with endurance over 1000 cycles.