Low-power Switching Devices Research Articles

Design Considerations for 2-D Dirac-Source FETs—Part I: Basic Operation and Device Parameters

Dirac-source field-effect transistors (DS-FETs) have been proposed as promising candidates for low-power switching devices by leveraging the Dirac cone of graphene as a low-pass energy filter. In particular, using 2-D materials as the channel in a DS-FET is of interest for ultimate scaling purposes. In this article, we investigate the design considerations for 2-D DS-FETs using ballistic simulations based on the Landauer formalism. We study the impact of several key device parameters on the device performance, such as graphene doping, Schottky barrier heights, and effective mass of the 2-D channel. In Part II of this article, we study the impact of nonidealities on the performance of DS-FETs and benchmark the performance of DS-FETs for different channel materials.

Realization of low-power and high mobility thin film transistors based on MoS2 layers grown by PLD technique

Molybdenum disulfide (MoS2) layers have been successfully grown and optimized for the realization of low power thin film transistors (TFTs) using catalysis free, economical and environment-friendly pulsed laser deposition (PLD) technique on comparably large sized passivated silicon (SiO2/Si) substrate of area 1.2 cm×1.0 cm. Growth of MoS2 monolayer is confirmed by reflection high-energy electron diffraction (RHEED), Raman spectroscopy, photoluminescence (PL) analysis and atomic force microscopy (AFM). The effect of planar electrodes of different metal system (Au/Ag, Pt/Ti, Al, Ni) on the electrical characteristics of MoS2 layers have been inspected in detail. Au/Ag bilayer system proved to be the best electrode for efficient charge injection into the MoS2 layers. A Back-gated field effect transistor (FET) was fabricated with Au/Ag was used as source-drain contacts and MoS2 as the semiconducting channel has been successfully developed. The fabricated transistor shows an accumulation electron mobility around 44.6 cm2 V-1s−1, current ION/OFF ratio of 1.4×105, subthreshold slope of nearly 360 mV/dec, interface trap density of 1.18×1012 /cm2eV and robust current saturation at lower Vds, suggesting that fabricated devices can be used in making low power switching devices.

Quasi-Clamped ZSI With Two Transformers

In this article, we present a new type of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> -source inverter (ZSI) that replaces two inductors in the original quasi-ZSI with two transformers. It can produce a very high output voltage with the high value of the modulation index. Moreover, it enables both to provide a better power quality of output and to reduce the switching loss. In particular, the proposed quasi-clamped ZSI with two transformers give a unique solution to obtain high gain by reducing the turns ratio, rather than increasing it. Also, the leakage inductance of the transformer might cause huge voltage spikes across the inverter bridge. To deal with this problem, an effective clamping technique is proposed. As a result, this increases the overall efficiency of the system by utilizing the low-power switching devices. The characteristics of the proposed quasi-clamped ZSI with two transformers are comprehensively discussed with the detailed theoretical analysis. Thereafter, its performances are evaluated by both simulation and experimental tests.

Metallic behavior in STO/LAO heterostructures with non-uniformly atomic interfaces

The search for new and low-power switching devices involving the integration of semiconductor thin films is of interest, and has led to renewed research because such devices may exhibit innovative properties. Here, we investigate the two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface with metallic and insulator behavior. Insight is offered by quantifying the interface charge distribution associated with structural and electronic order-disorder effects. Variations in the electron conductivity were observed to be associated with different specific clustering arrangements of both Ti and Al cations of the co-exposed surfaces at the interface, i.e., structural and electronic connectivity among the undercoordinated [TiO5] and [AlO5] clusters. These results indicate facet control as a strategy for enhancing the electric and magnetic properties of a device via the quantum confinement of electrons.

Effect of Oxide Thickness on GaN-based Double Gate MOSFETs

The effect of oxide thickness (EOT) on GaN-based double gate (DG) MOSFETs have been explored for low power switching device. The gate length (LG) of 8 nm with 4 nm underlap is considered. The device is turned off and on for gate voltage (VGS) of 0 V and 1 V, respectively. The effective oxide thickness (EOT) is varied from 1 nm to 0.5 nm and the device performance is evaluated. For EOT = 0.5 nm, the OFF-state current (IOFF), subthreshold slope (SS) and drain induced barrier lowering (DIBL) are obtained 2.97×10-8 A/μm, 69.67 mV/dec and 21.753 mV/V, respectively. These results indicate that, it is possible to minimize short channel effects (SCEs) by using smaller value of EOT.

Multi-input multi-output converter with battery charger for low power applications

For low power applications an integrated type multi- input multi- output converter with battery charger was presented in this paper. Power can be delivered from different sources with low power switching device using the proposed topology. The circuit model is designed to reduce the switching losses and to improve the converter overall efficiency by charging the battery using transformer leakage inductance. The input power distribution includes two input sources are operated by this converter model. This paper proposed a 20 –W prototype to test the converter performance and the experimental results are shown.

Control of the Magnetic Configuration of Ferromagnetic Nanostructures Across the Structural Phase Transition of Vanadium Dioxide

We investigate the effect of the structural phase transition in VO 2 in magnetoelastically coupled heterostructures of VO 2 and Ni. Continuous and nano-patterned Ni layers were used, and we found reversible and reproducible magnetic domain switching induced by the VO 2 structural phase transition. The magnetic states of the nano-patterned ferromagnetic elements were dominated by topographic features which generated strong pinning but still allowed for a reversible switching between the states. Our measurements constitute a key step for the use of the VO 2 phase transition for ultrafast dynamical studies of the inverse mangetostrictive effect, and eventually employing the effect for ultrafast low-power switching devices.

Two-dimensional Transition-metal Dichalcogenides for High-mobility and Low-power Transistors

The remarkable properties of graphene have made it the most widely studied two-dimensional material. However, its lack of a bandgap limits its transistor applications. Recently, interest in transistion-metal dichalcogenides, such as molybdenum disulfide (MoS2), has been growing rapidly because, unlike graphene, the existence of bandgaps, combined with mobility enhancement by dielectric engineering, offers an attractive possibility of using MoS2 field-effect transistors in low-power switching devices and photodetectors. Here, we review the historical development, properties and prospects of MoS2.

기판전압에 따른 나노와이어 Junctionless MuGFET의 전류-전압 특성

In this paper, a current-voltage characteristics of n-channel junctionless and inversion mode(IM) MuGFET, and p-channel junctionless and accumulation mode(AM) MuGFET has been measured and analyzed for the application in high speed and low power switching devices. From the variation of the threshold voltage and the saturation drain current with the substrate bias voltages, their variations in IM devices are larger than junctionless devices for n-channel devices, but their variations in junctioness devices are larger than AM devices for p-channel devices. The variations of transconductance with substrate biases are more significant in p-channel devices than n-channel devices. From the characteristics of subthreshold swing, it was observed that the S value is almost independent on the substrate biases in n-channel devices and p-channel junctionless devices but it is increased with the increase of the substrate biases in p-channel AM devices. For the application in high speed and low power switching devices using the substrate biases, IM device is better than junctionless devices for n-channel devices and junctionless device is better than AM devices for p-channel devices.

High-mobility and low-power thin-film transistors based on multilayer MoS2 crystals

Unlike graphene, the existence of bandgaps (1-2 eV) in the layered semiconductor molybdenum disulphide, combined with mobility enhancement by dielectric engineering, offers an attractive possibility of using single-layer molybdenum disulphide field-effect transistors in low-power switching devices. However, the complicated process of fabricating single-layer molybdenum disulphide with an additional high-k dielectric layer may significantly limit its compatibility with commercial fabrication. Here we show the first comprehensive investigation of process-friendly multilayer molybdenum disulphide field-effect transistors to demonstrate a compelling case for their applications in thin-film transistors. Our multilayer molybdenum disulphide field-effect transistors exhibited high mobilities (>100 cm(2) V(-1) s(-1)), near-ideal subthreshold swings (~70 mV per decade) and robust current saturation over a large voltage window. With simulations based on Shockley's long-channel transistor model and calculations of scattering mechanisms, these results provide potentially important implications in the fabrication of high-resolution large-area displays and further scientific investigation of various physical properties expected in other layered semiconductors.