Efficient compact model for calculating the surface potential of carbon-nanotube field-effect transistors using a curve-fitting method

This paper presents an analytical method to compute the surface potential of ballistic metal-oxide semiconductor field-effect transistor (MOSFET)-like carbon-nanotube field-effect transistors (CNFETs). The proposed compact model considers the surface potential as functions of the carbon-nanotube diameter, gate insulator thickness, gate voltage and drain voltage. One of the advantages of this model is that there is no need to refer to the numerical model to recalculate the surface potential each time nanotube diameter or insulator thickness is changed. Instead of using a constant smoothing parameter regardless of the device size and applied bias voltages, a parameter calculated for the specific situations is employed to provide the simulation results with higher accuracy. The validity of the proposed model was verified by comparing the simulated output characteristics of three CNFETs with those of the numerical model and the previous compact model.     

Scattering effects on the performance of carbon nanotube field effect transistor in a compact model

Carbon nanotube field-effect transistors (CNTFET) are being extensively studied as possible successors to CMOS. Device simulators have been developed to estimate their performance in sub-10-nm and device structures have been fabricated. In this work, a new compact model of single-walled semiconducting CNTFET is proposed implementing the calculation of energy conduction sub-band minima and the treatment of scattering effects through energy shift in CNTFET. The developed model has been used to simulate I-V characteristics using VHDL-AMS simulator.     

Conjugated polymer-wrapped carbon nanotubes: physical properties and device applications

The aim of this article is to present an overview about the preparation method and physical properties of a new hybrid system consisting of single-walled carbon nanotubes (SWNTs) wrapped by conjugated polymers. The technique firstly demonstrated in 2007 has attracted great interest because of the high purity of the resulting semiconducting SWNTs and the possibility of applying them in electronic devices. Here, we will review recent progresses regarding the preparation of these nano-hybrids, their photophysical properties and application in field-effect transistors and photovoltaic devices.     

Review of gallium oxide based field-effect transistors and Schottky barrier diodes

Gallium oxide(Ga_2O_3), a typical ultra wide bandgap semiconductor, with a bandgap of ~4.9 e V, critical breakdown field of 8 MV/cm, and Baliga's figure of merit of 3444, is promising to be used in high-power and high-voltage devices.Recently, a keen interest in employing Ga_2O_3 in power devices has been aroused. Many researches have verified that Ga_2O_3 is an ideal candidate for fabricating power devices. In this review, we summarized the recent progress of field-effect transistors(FETs) and Schottky barrier diodes(SBDs) based on Ga_2O_3, which may provide a guideline for Ga_2O_3 to be preferably used in power devices fabrication.     

Direct top–down fabrication of nanoscale electrodes for organic semiconductors using fluoropolymer resists

We report the use of a fluoropolymer resist for the damage-free e-beam lithographic patterning of organic semiconductors. The same material is also shown to be suitable as an orthogonal electron beam resist for the patterning of top-contact electrodes on organic thin films. We demonstrate this by characterizing pentacene field-effect transistors with feature sizes as small as 100 nm and compare the performance of bottom- and top-contacted devices.     

Self-Consistent Study of Conjugated Aromatic Molecular Transistors

We study the current through conjugated aromatic molecular transistors modulated by a transverse field. The selfconsistent calculation is realized with density function theory through the standard quantum chemistry software Gaussian03 and the non-equilibrium Green＇s function formalism. The calculated I - V curves controlled by the transverse field present the characteristics of different organic molecular transistors, the transverse field effect of which is improved by the substitutions of nitrogen atoms or fluorine atoms. On the other hand, the asymmetry of molecular configurations to the axis connecting two sulfur atoms is in favor of realizing the transverse field modulation. Suitably designed conjugated aromatic molecular transistors possess different I - V characteristics, some of them are similar to those of metal-oxide-semiconductor field-effect transistors （MOSFET）. Some of the calculated molecular devices may work as elements in graphene electronics. Our results present the richness and flexibility of molecular transistors, which describe the colorful prospect of next generation devices.     

Quantum compact model for thin-body double-gate Schottky barrier MOSFETs

Nanoscale Schottky barrier metal oxide semiconductor field-effect transistors （MOSFETs） are explored by using quantum mechanism effects for thin-body devices. The results suggest that for small nonnegative Schottky barrier heights, even for zero barrier height, the tunnelling current also plays a role in the total on-state current. Owing to the thin body of device, quantum confinement raises the electron energy levels in the silicon, and the tradeoff takes place between the quantum confinement energy and Schottky barrier lowering （SBL）. It is concluded that the inclusion of the quantum mechanism effect in this model, which considers an infinite rectangular well with a first-order perturbation in the channel, can lead to the good agreement with numerical result for thin silicon film. The error increases with silicon thickness increasing.     

Effect of interfacial shallow traps on polaron transport at the surface of organic semiconductors

The photo-induced electron and hole transfer across the semiconductor-dielectric interface in trap-dominated p-type organic field-effect transistors has been investigated. It has been observed that the transfer of electrons into the dielectric results in a decrease of the field-effect mobility of polarons, suggesting that additional shallow traps are generated in the conduction channel. Using this effect, the dependence of the field-effect mobility on the density of shallow traps, mu(N), has been measured, which allowed us to estimate the average polaron trapping time, tau_{tr}=50+/-10 ps, and the density of shallow traps, N0=(3+/-0.5) x 10(11) cm(-2), in the channel of single-crystal tetracene devices.     

高质量单层二硫化钼薄膜的研究进展

作为一种新型的二维半导体材料,单层二硫化钼薄膜由于其优异的特性,在电子学与光电子学等众多领域具有潜在的应用价值.本文综述了我们课题组在过去几年中针对单层二硫化钼薄膜的研究所取得的进展,具体包括:在二硫化钼薄膜的制备方面,通过氧辅助化学气相沉积方法,实现了大尺寸单层二硫化钼单晶的可控生长和晶圆级单层二硫化钼薄膜的高定向外延生长;在二硫化钼薄膜的加工方面,发展了单层二硫化钼薄膜的无损转移、洁净图案化加工、可控结构相变与局域相调控的方法,为场效应晶体管等电子学器件的制备与性能优化提供了基础;在二硫化钼异质结方面,研究了二硫化钼薄膜与其他二维材料形成的异质结的电学以及光电性质,为二维材料异质结的构筑和器件特性研究提供了实验参考;在二硫化钼薄膜功能化器件与应用方面,构筑了全二维材料、亚5 nm超短沟道场效应晶体管器件,验证了单层二硫化钼对短沟道效应的有效抑制及其在5 nm工艺节点器件中的应用优势;此外,利用制备的高质量单层二硫化钼和发展的器件洁净加工技术,实现了高性能柔性薄膜晶体管的集成,获得了超高灵敏度与稳定性的非接触型湿度传感器.我们在二硫化钼薄膜的制备、加工以及器件特性研究方面所取得的进展对于二硫化钼及其他二维过渡金属硫属化合物的基础和应用研究均具有指导意义.     

Memory element based on ferroelectric field-effect transistor with use of ZnO:Li/LaB6 heterostructures

Ferroelectric field-effect transistors using ZnO:Li films simultaneously as a transistor channel and as a ferroelectric active element have been prepared and studied. We show an opportunity of using the ferroelectric field-effect transistor based on ZnO:Li films in ZnO:Li/LaB₆ heterostructure as a bistable memory element for information recording. The proposed structure of a ferroelectric memory cell does not possess the fatigue under repeated readout of single recorded information that will allow increasing the resource of storage devices essentially.     

Multimode transport in Schottky-barrier carbon-nanotube field-effect transistors

We present a detailed study on the impact of multimode transport in carbon nanotube field-effect transistors. Under certain field conditions electrical characteristics of tube devices are a result of the contributions of more than one one-dimensional subband. Through potassium doping of the nanotube the impact of the different bands is made visible. We discuss the importance of scattering for a stepwise change of current as a function of gate voltage and explain the implications of our observations for the performance of nanotube transistors.     

高迁移率聚合物薄膜晶体管

以高掺杂Si单晶片作为栅电极, 热生长SiO₂作为栅介质层, 聚三己基噻吩薄膜作为半导体活性层, Au作为源、漏电极, 并采用十八烷基三氯硅烷（OTS）对栅介质表面改性, 在空气环境下成功地制备出高性能聚合物薄膜晶体管. 结果表明, 通过采用OTS对栅介质层表面修饰大幅度地改善了聚合物薄膜晶体管的电性能, 器件的场效应迁移率高达0.02 cm²/（Vs）, 开关电流比大于10⁵. 关键词： 聚合物薄膜晶体管 聚三己基噻吩 场效应迁移率 表面修饰     

Subthreshold regime in rubrene single-crystal organic transistors

Organic field-effect transistors were fabricated with vapor-grown rubrene single crystals in a staggered top-contact configuration. The devices were electrically characterized by measuring the transfer curves at low drain voltage. In parallel to these measurements, a model is developed to account for the subthreshold regime of the transistors. The model is based on the multiple trapping and thermal release concept, which assumes that charge transport is limited by a single level of shallow traps located close to the transport band edge. It is shown that the threshold voltage no longer establishes at the transition between the depletion and accumulation regimes. Instead, the threshold corresponds to the point at which traps are filled. This results in a subthreshold current that varies linearly with gate voltage. Moreover, the subthreshold current at low drain voltages increases with drain voltage. These finding are in good agreement with the experimental data.     

Meyer–Neldel rule in fullerene field-effect transistors

The temperature dependence of the field-effect mobility is investigated in vacuum evaporated C₆₀-based organic field-effect transistors. The results show a thermally activated behavior with an activation energy that depends on the field-induced charge carrier density in the transistor channel. Upon extrapolation of the data in an Arrhenius plot we find an empirical relation, termed the Meyer–Neldel rule, which states that the mobility prefactor increases exponentially with the activation energy. Based on this analysis a characteristic temperature is extracted. The possible implications of this observation in terms of charge transport in fullerene-based field-effect transistors are discussed.     

Noise Factor of Optically Controlled GaAs Field-Effect Transistors

The influence of IR radiation on the noise factor of GaAs field-effect transistors has been analyzed. It is shown that the noise factor of the indicated transistors decreases under IR irradiation. It has been established that a decrease in the noise factor of the field-effect transistors under IR irradiation is mainly due to an increase in the low-field mobility of electrons in them.     

Electron transport and terahertz radiation detection in submicrometer-sized GaAs/AlGaAs field-effect transistors with two-dimensional electron gas

The electronic transport and response in the terahertz range are studied in field-effect GaAs/AlGaAs transistors with a two-dimensional high-mobility electron gas. The special interest expressed in such transistors stems from the possibility of developing terahertz-range radiation detectors and generators on the basis of these devices. Measurements of the value and the magnetic-field dependence of the drain-source resistance are used to estimate the electron density and mobility in the transistor channel. Results of magnetotransport measurements are employed to interpret the nonresonant detection observed in transistors with a gate width from 0.8 to 2.5 μm. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 146–149. Original Russian Text Copyright ? 2004 by Antonov, Gavrilenko, Demidov, Morozov, Dubinov, Lusakowski, Knap, Dyakonova, Kaminska, Piotrowska, Golaszewska, Shur.     

Design and investigation of novel ultra-high-voltage junction field-effect transistor embedded with NPN

Ultra-high-voltage(UHV) junction field-effect transistors(JFETs) embedded separately with the lateral NPN(JFETLNPN), and the lateral and vertical NPN(JFET-LVNPN), are demonstrated experimentally for improving the electrostatic discharge(ESD) robustness. The ESD characteristics show that both JFET-LNPN and JFET-LVNPN can pass the 5.5-k V human body model(HBM) test. The JFETs embedded with different NPNs have 3.75 times stronger in ESD robustness than the conventional JFET. The failure analysis of the devices is performed with scanning electron microscopy, and the obtained delayer images illustrate that the JFETs embedded with NPN transistors have good voltage endurance capabilities. Finally,the internal physical mechanism of the JFETs embedded with different NPNs is investigated with emission microscopy and Sentaurus simulation, and the results confirm that the JFET-LVNPN has stronger ESD robustness than the JFET-LNPN,because the vertical NPN has a better electron collecting capacity. The JFET-LVNPN is helpful in providing a strong ESD protection and functions for a power device.     

Hybrid semiconductor/metal nanostructures with two-dimensional electron systems

A brief account of our recent work on InAs/metal hybrids is given. In particular we discuss Josephson field-effect transistors with niobium source and drain contacts, first spin transistor structures with permalloy electrodes, and devices with gold shunts exhibiting the extraordinary magnetoresistance effect.     

Fabrication and characteristics of lateral Ti/4H-SiC Schottky barrier diodes

This paper describes the fabrication and characteristics of the lateral Ti/4H-SiC Schottky barrier diodes (SBDs). SBDs are fabricated by nitrogen ion implantation into p-type 4H-SiC epitaxial layer. The implant depth profile is simulated using the Monte Carlo simulator TRIM. Measurements of the reverse I－V characteristics demonstrate a low reverse current, that is good enough for many SiC-based devices such as SiC metal-semiconductor field-effect transistors, and SiC static induction transistors. The parameters of the diodes are extracted from the forward I－V characteristics. The barrier height φ_b of Ti/4H-SiC is 0.95 eV.     

Lateral scaling in carbon-nanotube field-effect transistors

We have fabricated carbon-nanotube (CN) field-effect transistors with multiple, individually addressable gate segments. The devices exhibit markedly different transistor characteristics when switched using gate segments controlling the device interior versus those near the source and drain. We ascribe this difference to a change from Schottky-barrier modulation at the contacts to bulk switching. We also find that the current through the bulk portion is independent of gate length for any gate voltage, offering direct evidence for ballistic transport in semiconducting carbon nanotubes over at least a few hundred nanometers, even for relatively small carrier velocities.