我们研究了Si/SiO_2衬底上的氮化硼-石墨烯-氮化硼异质结场效应晶体管的低频1/f噪声（f为频率）。该器件沟道是用包裹在两层六方氮化硼之间的单层石墨烯实现的。该晶体管在室温下的载流子迁移率在30000至36000 cm 2/Vs的范围内。已经确定，在这种器件中，归一化到沟道面积的噪声谱密度可以被抑制到5 x 10^-9 μm2 Hz^-1，这比Si/SiO2上的非封装石墨烯器件低x5 - x10倍。噪声抑制的物理机制归因于沟道中的载流子与SiO2栅介质中的陷阱和表面缺陷的屏蔽。所得结果对石墨烯的电子和光电应用具有重要意义。
英文摘要：
We have investigated low-frequency 1/f noise in the boron nitride - grapheme - boron nitride heterostructure field - effect transistors on Si/SiO2 substrates (f is a frequency). The device channel was implemented with a single layer graphene encased between two layers of hexagonal boron nitride. The transistors had the charge carrier mobility in the range from 30000 to 36000 cm2/Vs at room temperature. It was established that the noise spectral density normalized to the channel area in such devices can be suppressed to 5 x 10^-9 μm2 Hz^-1, which is a factor of x5 - x10 lower than that in non-encapsulated graphene devices on Si/SiO2. The physical mechanism of noise suppression was attributed to screening of the charge carriers in the channel from traps in SiO2 gate dielectric and surface defects. The obtained results are important for the electronic and optoelectronic applications of graphene.
Quantum engineering entails atom by atom design and fabrication of electronic devices. This innovative technology that unifies materials science and device engineering has been fostered by the recent progress in the fabrication of vertical and lateral heterostructures of two-dimensional materials and by the assessment of the technology potential via computational nanotechnology. But how close are we to the possibility of practical realisation of the next generation atomically thin transistors? In this perspective we analyse the outlook and the challenges of quantum- engineered transistors usin…
In this paper we propose two transistor concepts based on lateral heterostructures of monolayer MoS$_2$, composed of adjacent regions of 1T (metallic) and 2H (semiconducting) phases, inspired by recent research showing the possibility to obtain such heterostructures by electron beam irradiation. The first concept, the lateral heterostructure field-effect transistor, exhibits potential of better performance with respect to the foreseen evolution of CMOS technology, both for high performance and low power applications. Performance potential has been evaluated by means of detailed multi-scale mat…
We have fabricated and measured ballistic graphene transistors with two oblique gates that can be independently biased. The gate lengths are about 38 nm and are separated by a distance of 30 nm, the tilting angle being of 45o with respect to source and drain electrodes distanced at 190 nm. Electric measurements reveal specific properties of ballistic carrier transport, i.e. nonlinear drain voltage-drain current dependence, showing a saturation region, and negative differential resistance at certain bias voltages, which cannot be explained without physical mechanisms related to ballistic transp…
Performance Evaluation of Ballistic Silicon Nanowire Transistors with Atomic-basis Dispersion Relations
在这封信中，我们探讨了能带结构对弹道硅纳米线晶体管（SNWT）性能的影响。用sp 3d 5s * 紧束缚模型计算了硅纳米线的能量色散关系。基于计算的色散关系，弹道电流的n型和p型SNWT的评估通过使用半数值弹道模型。对于大直径的纳米线，我们发现，弹道p-SNWT提供一半的弹道n-SNWT的ON电流。然而，对于小直径，p型SNWT的导通电流接近其n型对应物。最后，SNWTs的载流子注入速度与平面金属氧化物半导体场效应晶体管进行了比较，清楚地表明了量子限制对SNWTs性能极限的影响。
Graphene/silicon heterostructures have attracted tremendous interest as a new platform for diverse electronic and photonic devices such as barristors, solar cells, optical modulators, and chemical sensors. The studies to date largely focus on junctions between graphene and lightly-doped silicon, where a Schottky barrier is believed to dominate the carrier transport process. Here we report a systematic investigation of carrier transport across the heterojunctions formed between graphene and highly-doped silicon. By varying the silicon doping level and the measurement temperature, we show that t…
We show that by adding only two fitting parameters to a purely ballistic transport model, we can accurately characterize the current-voltage characteristics of nanoscale MOSFETs. The model is an extension to a ballistic model (J. Appl. Phys. 76, 4879 (1994)) and includes transmission probability and the drain-channel coupling capacitor. The latter parameter gives rise to a theoretical RON that is significantly larger than those predicted previously. To validate our model, we fabricated n-channel MOSFETs with varying channel lengths. We show the length dependence of these parameters to support …
We analyze the operation of the graphene n+-i-n-n+ field-effect transistors (GFETs) and lateral diodes (GLDs) with the injection of ballistic electrons into the n-region. The momentum transfer of the injected ballistic electrons could lead to an effective Coulomb drag of the quasi-equilibrium electrons in the n-region and the plasma instability in the GFETs and GLDs. The instability enables the generation of terahertz radiation. The obtained results can be used for the optimization of the structures under consideration for different devices, in particular, terahertz emitters.
A new analytical model based on the WKB approximation for MOSFET-like one-dimensional ballistic transistors with Schottky-Barrier contacts has been developed for the drain current. By using a proper approximation of both the Fermi-Dirac distribution function and transmission probability, an analytical solution for the Landauer integral was obtained, which overcomes the limitations of existing models and extends their applicability toward high bias voltages needed for analog applications. The simulations of transfer and output characteristics are found to be in agreement with the experimental d…
Initiating impact ionization of avalanche breakdown essentially requires applying a high electric field in a long active region, hampering carrier-multiplication with high gain, low bias and superior noise performance. Here we report the observation of ballistic avalanche phenomena in sub-MFP scaled vertical indium selenide (InSe)/black phosphorus (BP) heterostructures. The heterojunction is engineered to avalanche photodetectors (APD) and impact ionization transistors, demonstrating ultra-sensitive mid-IR light detection (4 μm wavelength) and ultra-steep subthreshold swing, respectively. Thes…
We demonstrate a graphene-MoS2 architecture integrating multiple field-effect transistors and we independently probe and correlate the conducting properties of van der Waals coupled graphene-MoS2 contacts with the ones of the MoS2 channels. Devices are fabricated starting from high-quality single-crystal monolayers grown by chemical vapor deposition and characterized by scanning Raman and photoluminescence spectroscopies. Transconductance curves of MoS2 are compared with the current-voltage characteristics of graphene contact stripes, revealing a significant suppression of transport on the n-s…
A simple model based on the WKB approximation for one-dimensional ballistic multi--gate reconfigurable field--effect transistors (RFETs) with Schottky-Barrier contacts has been developed for the drain current taking into account electron and hole band-to-band tunneling. By using a proper approximation of both the Fermi-Dirac distribution function and transmission probability, an analytical solution for the Landauer integral can be obtained. A comparative analysis of the two-gate and triple-gate RFETs is performed based on the numerical integration of the current integral.
Field-effect transistors made of wide-bandgap semiconductors can operate at high voltages, temperatures and frequencies with low energy losses, and have been of increasing importance in power and high-frequency electronics. However, the poor performance of p-channel transistors compared with that of n-channel transistors has constrained the production of energy-efficient complimentary circuits with integrated n- and p-channel transistors. The p-type surface conductivity of hydrogen-terminated diamond offers great potential for solving this problem, but surface transfer doping, which is commonl…
Spin transistors (whose on-off operation is achieved by electric-field-controlled spin orientation 1), if realized, can revolutionize modern electronics through the implementation of a faster and a more energy-efficient performance as well as non-volatile data storage 2, 3. The original proposal by Datta and Das 1 that relies on electric-field-controlled spin precession in a semiconductor channel faces significant challenges including inefficient spin injection, spin relaxation and spread of the spin precession angle 4, 5. Recent demonstration of electric-field switching of magnetic order 6-8 …
To develop effective thermal management strategies for GaN transistors, it is essential to accurately predict the device junction temperature. Since the width of the heat generation in the devices is comparable to phonon mean free paths of GaN, phonon ballistic transport exists and can significantly affect the heat transport process, which necessitates a thorough understanding of the influence of the phonon ballistic effects in GaN transistors. In this paper, the ballistic-diffusive phonon transport in GaN-on-SiC devices is examined by measuring the hotspot temperature using the thermoreflecta…
There is a wide range of science and applications accessible via the strain engineering of quantum transport in 2D materials. We propose a realistic experimental platform for uniaxial strain engineering of ballistic charge transport in graphene. We then develop an applied theoretical model, based on this platform, to calculate charge conductivity and demonstrate graphene quantum strain transistors (GQSTs). We define GQSTs as mechanically strained ballistic graphene transistors with on/off conductivity ratios $> 10^{4}$, and which can be operated via modest gate voltages. Such devices would per…
We demonstrate that the injection of the ballistic electrons into the two-dimensional electron plasma in lateral n$^+$-i-n-n$^+$ graphene field-effect transistors (G-FET) might lead to a substantial Coulomb drag of the quasi-equilibrium electrons due the violation of the Galilean and Lorentz invariance in the systems with a linear electron dispersion. This effect can result in the S-shaped current-voltage characteristics (IVs). The resulting negative differential conductivity enables the hysteresis effects and current filamentation that can be used for the implementation of voltage switching d…
Quantum ballistic transport in in-plane-gate transistors showing onset of a novel ferromagnetic phase transition
我们研究了聚焦离子束写入III-V族异质结平面栅晶体管中的一维输运，温度适中，零偏置，无任何外部磁场施加。根据A.黄金和L。准一维电子气中的谷位和自旋占据不稳定性。Mag. Lett. 74，33-42（1996）和早期的实验数据，我们观察到源-漏电导率的平台被认为是栅极电压的函数，不仅在2e^2/h的倍数处，而且在e^2/h处也很明显，就在沟道接近零电导率之前。这可以解释为一种多电子效应，即一种新的弹道铁磁基态，避开了标准的描述和定理。
On the Bandstructure Velocity and Ballistic Current of Ultra Narrow Silicon Nanowire Transistors as a Function of Cross Section Size, Orientation and Bias
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…
Valley degree of freedom in the 2D semiconductor is a promising platform for the next generation optoelectronics. Electrons in different valleys can have opposite Berry curvature, leading to the valley Hall effect (VHE). However, VHE without the plasmonic structure's assistance has only been reported in cryogenic temperature, limiting its practical application. Here, we report the observation of VHE at room temperature in the MoS2/WSe2 heterostructures. We also uncover that both the magnitude and the polarity of the VHE in the 2D heterostructure is gate tunable. We attribute this to the opposi…
Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, both vertical (van der Waals) and in-plane, offer an unprecedented control over the properties and functionalities of the resulted structures. Thus, planar heterostructures allow p-n junctions between different two-dimensional semiconductors and graphene nanoribbons with well-defined edges; and vertical heterostructures resulted in the observation of superconductivity in purely carbon-based systems and realisation of vertical tunnelling transistors. Here we demonstrate simultaneous use of in-plane an…
Simulations of Nanowire Transistors: Atomistic vs. Effective Mass Models
采用10轨道sp 3d 5s * 原子紧束缚模型描述纳米线晶体管的电子结构，采用势垒顶半经典弹道模型计算纳米线晶体管的输运性质，研究了纳米线晶体管中电子输运的弹道性能.色散是自洽计算的二维泊松解的静电势的截面的导线。在强量子化下，纳米线的有效质量从体值显著变化，并且谷分裂等效应强烈地提升了谷的简并性。这些效应在用电荷填充晶格的情况下甚至更明显。有效质量近似仅在某些情况下与紧束缚模型在电流-电压特性方面吻合得很好。一般来说，对于小直径导线，有效质量近似失效。
We demonstrate a tunnel field effect transistor based on a lateral heterostructure patterned from an $\mathrm{LaAlO_3/SrTiO_3}$ electron gas. Charge is injected by tunneling from the $\mathrm{LaAlO_3}$/$\mathrm{SrTiO_3}$ contacts and the current through a narrow channel of insulating $\mathrm{SrTiO_3}$ is controlled via an electrostatic side gate. Drain-source I/V-curves have been measured at low and elevated temperatures. The transistor shows strong electric-field and temperature-dependent behaviour with a steep sub-threshold slope %of up to as small as $10\:\mathrm{mV/decade}$ and a transcon…
We report on ultra-wide bandgap (UWBG) Al0.75Ga0.25N channel metal-insulator-semiconductor field-effect transistors (MISFET) with heterostructure engineered low-resistance ohmic contacts. The low intrinsic electron affinity of AlN (0.6 eV) leads to large Schottky barriers at metal-AlGaN interface, resulting in highly resistive ohmic contacts. In this work, we use reverse compositional graded n++ AlGaN contact layer to achieve upward electron affinity grading, leading to a low specific contact resistance of 1.9x10-6 ohm.cm2 to n-Al0.75Ga0.25N channels (bandgap ~ 5.3 eV) with non-alloyed contact…
Cold source field-effect transistor with type-III band-aligned HfS$_2$/WTe$_2$ heterostructure
College of Physics and Electronic Engineering and Center for Computational Sciences, Sichuan Normal University（四川师范大学物理与电子工程学院及计算科学中心）；Centre for the Physics of Materials and Department of Physics, McGill University（麦吉尔大学材料物理中心及物理系）；School of Integrated Circuit, Peking University（北京大学集成电路学院）；Beijing Advanced Innovation Center for Integrated Circuits（北京集成电路先进创新中心）；College of Physics and Optoelectronic Engineering, Shenzhen University（深圳大学物理与光电工程学院）
We study time-dependent electron transport and quantum noise in a ballistic graphene field effect transistor driven by an ac gate potential. The non-linear response to the ac signal is computed through Floquet theory for scattering states and Landauer-Büttiker theory for charge current and its fluctuations. Photon-assisted excitation of a quasibound state in the top-gate barrier leads to resonances in transmission that strongly influence the noise properties. For strong doping of graphene under source and drain contacts, when electrons are transmitted through the channel via evanescent waves, …
Nanostructures based on buried interfaces and heterostructures are at the heart of modern semiconductor electronics as well as future devices utilizing spintronics, multiferroics, topological effects and other novel operational principles. Knowledge of electronic structure of these systems resolved in electron momentum k delivers unprecedented insights into their physics. Here, we explore 2D electron gas formed in GaN/AlGaN high-electron-mobility transistor (HEMT) heterostructures with an ultrathin barrier layer, key elements in current high-frequency and high-power electronics. Its electronic…
The vertical stacking of van der Waals (vdW) materials introduces a new degree of freedom to the research of two-dimensional (2D) systems. The interlayer coupling strongly influences the band structure of the heterostructures, resulting in novel properties that can be utilized for electronic and optoelectronic applications. Based on microwave microscopy studies, we report quantitative electrical imaging on gated molybdenum disulfide (MoS2)/tungsten diselenide (WSe2) heterostructure devices, which exhibit an intriguing anti-ambipolar effect in the transfer characteristics. Interestingly, in the…
We propose and investigate the intrinsically thinnest transistor concept: a monolayer ballistic heterojunction bipolar transistor based on a lateral heterostructure of transition metal dichalcogenides. The device is intrinsically thinner than a Field Effect Transistor because it does not need a top or bottom gate, since transport is controlled by the electrochemical potential of the base electrode. As typical of bipolar transistors, the collector current undergoes a tenfold increase for each 60 mV increase of the base voltage over several orders of magnitude at room temperature, without sophis…
We study the impact of the ferroelectric domain wall on the ballistic conductance of the single-layer graphene channel in the heterostructure graphene / physical gap / ferroelectric film using Wentzel-Kramers-Brillouin approximation. Both self-consistent numerical modeling of the electric field and space charge dynamics in the heterostructure and approximate analytical theory show that the domain wall contact with the surface creates p-n junction in graphene channel. We calculated that the carriers' concentration induced in graphene by uncompensated ferroelectric dipoles originated from the sp…
Two-dimensional (2D) heterointerfaces often provide extraordinary carrier transport as exemplified by superconductivity or excitonic superfluidity. Recently, double-layer graphene separated by few-layered boron nitride demonstrated the Coulomb drag phenomenon: carriers in the active layer drag the carriers in the passive layer. Here, we propose a new switching device operating via Coulomb drag interaction at a graphene/MoS2 (GM) heterointerface. The ideal van der Waals distance allows strong coupling of the interlayer electron-hole pairs, whose recombination is prevented by the Schottky barrie…
