Nanotransistors typically operate in far-from-equilibrium (FFE) conditions, that cannot be described neither by drift-diffusion, nor by purely ballistic models. In carbonbased nanotransistors, source and drain contacts are often characterized by the formation of Schottky Barriers (SBs), with strong influence on transport. Here we present a model for onedimensional field-effect transistors (FETs), taking into account on equal footing both SB contacts and FFE transport regime. Intermediate transport is introduced within the Buttiker probe approach to dissipative transport, in which a non-ballistic transistor is seen as a suitable series of individually ballistic channels. Our model permits the study of the interplay of SBs and ambipolar FFE transport, and in particular of the transition between SB-limited and dissipation-limited transport.
We discuss the high-bias electrical characteristics of back-gated field-effect transistors with CVD-synthesized bilayer MoS2 channel and Ti Schottky contacts. We find that oxidized Ti contacts on MoS2 form rectifying junctions with ~0.3 to 0.5 eV Schottky barrier height. To explain the rectifying output characteristics of the transistors, we propose a model based on two slightly asymmetric back-to-back Schottky barriers, where the highest current arises from image force barrier lowering at the electrically forced junction, while the reverse current is due to Schottky-barrier limited injection …
The Effect of Dielectric Capping on Few-Layer Phosphorene Transistors: Tuning the Schottky Barrier Heights
磷烯是一种独特的具有二维层状结构的单元素半导体。在这封信中，我们研究了机械剥离的少层磷烯顶栅晶体管的行为。我们实现了144 mA/mm的高导通电流和95.6 cm 2/Vs的空穴迁移率。我们沉积Al 2 O3原子层沉积（ALD）和研究的电介质覆盖的影响。我们观察到，晶体管的极性交替从p型到双极与Al 2 O 3生长在顶部。我们将这种转变归因于金属接触边缘处的电子和空穴的有效肖特基势垒高度的变化，这源于ALD电介质中的固定电荷。
The potential barrier height at the interface formed by a metal contact and multiple one-dimensional (1D) quasi-ballistic channels in field-effect transistors (FETs) is evaluated across different carbon nanotube and nanowire device technologies by means of a Landauer-Büttiker-based extraction methodology (LBM) adapted for multiple 1D-channels. The extraction methodology yields values for an effective Schottky barrier height and a gate coupling coefficient, an indicator of the device working at the quantum capacitance limit. The novel LBM-based approach embracing the mechanisms in 1D electronic…
Cryogenic low noise amplifiers based on high electron mobility transistors (HEMTs) are widely used in applications such as radio astronomy, deep space communications, and quantum computing, and the physical mechanisms governing the microwave noise figure are therefore of practical interest. In particular, the contribution of thermal noise from the gate at cryogenic temperatures remains unclear owing to a lack of experimental measurements of thermal resistance under these conditions. Here, we report measurements of gate junction temperature and thermal resistance in a HEMT at cryogenic and room…
Schottky barriers in carbon nanotube heterojunctions
我们研究了金属和半导体单壁碳纳米管之间的异质结的电子性质。与传统的半导体异质结构相比，一维纳米管系统中长程库仑相互作用的无效屏蔽大大改变了电荷转移现象。耗尽区的长度在很宽的范围内（从纳米管半径到纳米管长度）敏感地取决于掺杂强度而变化。肖特基势垒引起异质结的I-V特性的不对称性，这与Yao { \it et al.}和Fuhrer { \it et al.}动态电荷积累结附近的结果在一个阶梯状增长的电流在反向偏置。
This work deals with the electron beam irradiation of the Schottky metal contacts in monolayer molybdenum disulfide (MoS$_2$) field-effect transistors (FETs). We show that the exposure of the Ti/Au source/drain leads to an electron beam improves the transistor conductance. We simulate the path of the electrons in the device and show that most of the beam energy is absorbed in the metal contacts. Hence, we propose that the transistor current enhancement is due to thermally induced interfacial reactions that lower the contact Schottky barriers. We also show that the electron beam conditioning of…
Engineering Schottky Barrier in Black Phosphorus field effect devices for spintronic applications
黑磷（BP）是近年来发现的一种很有前途的二维直接带隙半导体材料。在这里，我们报告的双极场效应晶体管的行为多层BP铁磁隧道接触。通过使用TiO ${_2}$ /Co接触，我们观察到肖特基势垒降低< 50 meV，这可以通过栅极电压进一步调节。突出地，在BP器件中实现了良好的晶体管性能，其中漏极电流调制在四到六个数量级上。在室温下，空穴和电子的载流子迁移率分别为$\sim$ 155和0.18 cm ${^2}$ V ${^{-1}}$ s ${^{-1}}$.此外，磁阻计算表明，与施加的栅极电压的BP设备的电阻是在适当的范围内注入和检测自旋极化的空穴。我们的研究结果表明，工程BP nanolayered器件的有效的纳米电子和自旋电子学应用的前景。
Two-dimensional material-based field effect transistors (2DM-FETs) are playing a revolutionary role in electronic devices. However, after years of development, no device model can match the Pao-Sah model for standard silicon-based transistors in terms of physical accuracy and computational efficiency to support large-scale integrated circuit design. One remaining critical obstacle is the contacts of 2DM-FETs. In order to self-consistently include the contact effect in the current model, it is necessary to perform self-consistent calculations, which is a fatal flaw for applications that priorit…
An increase in power consumption necessitates a low-power circuit technology to extend Moore's law. Low-power transistors, such as tunnel field-effect transistors (TFETs), negative-capacitance field-effect transistors (NC-FETs), and Dirac-source field-effect transistors (DS-FETs), have been realised to break the thermionic limit of the subthreshold swing (SS). However, a low-power diode rectifier, which breaks the thermionic limit of an ideality factor (n) of 1 at room temperature, has not been proposed yet. In this study, we have realised a DS Schottky diode, which exhibits a steep-slope char…
To explore the potential of field-effect transistors (FETs) based on monolayers of the two-dimensional semiconducting channel(SC) for spintronics, the two most important issues are to ensure the formation of variable low resistive tunnel ferromagnetic contacts(FC), and to preserve intrinsic properties of the SC during fabrication. Large Schottky barriers lead to the formation of high resistive contacts and methods adopted to control the barriers often alter the intrinsic properties of the SC. This work aims at addressing both issues in fully encapsulated monolayer WSe$_2$ FETs by using bi-laye…
Intrinsic carrier mobility of multi-layered MoS$_2$ field-effect transistors on SiO$_2$
通过制备和表征四端结构的多层MoS $_2$基场效应晶体管（FET），我们证明了由于接触处的肖特基势垒，两端结构倾向于低估载流子迁移率$μ$。对于背栅双端配置，我们观察到高达125 cm $^2$ V $^{-1}$ s $^{-1}$的迁移率，其显著小于当使用四端配置时从相同器件提取的306.5 cm $^2$ V $^{-1}$ s $^{-1}$。这表明在SiO $_2$上的MoS $_2$的本征迁移率明显大于先前报道的值，并提供了一种定量方法来评估通过接触的电荷传输。
The two-dimensional transition metal dichalcogenides (TMDs) have been proposed as candidates for the channel material in future field effect transistor designs. The heterophase design which utilizes the metallic T- or T' phase of the TMD as contacts to the semiconducting H phase channel has shown promising results in terms of bringing down the contact resistance of the device. In this work, we use ab-initio calculations to demonstrate how atomic-scale and quantum effects influence the ballistic transport properties in such heterophase transistors with channel lengths up to 20 nm. We investigat…
We demonstrate sensitive and fast electrical measurements of a carbon nanotube mechanical resonator. The nanotube is configured as a single-electron transistor, whose conductance is a sensitive transducer for its own displacement. Using an impedance-matching circuit followed by a cryogenic amplifier, the vibrations can be monitored in real time. The sensitivity of this continuous displacement measurement approaches within a factor 470 of the standard quantum limit.
