Three-terminal Ballistic Junctions Research Articles

The anisotropic transport properties of the three-terminal ballistic junction based on α−T 3 lattice

The three-terminal ballistic junction (TBJ) has promising applications in nanoelectronics. We investigate the transport properties of a α−T 3-based TBJ, where two typical configurations are considered, i.e. the A- and Z-TBJ. It is found that both A- and Z-TBJ exhibit transmission anisotropy, and the transmission of the A-TBJ has stronger anisotropy than that of the Z-TBJ. The amplitude of the rectification coefficient is smaller than that of phosphorene TBJ, but larger than that of graphene TBJ. When the symmetrical input is applied, the output voltage curve exhibits symmetric behavior. While in the case of asymmetric input, the symmetric behavior is broken, and the maximum value of the output voltage can reach a positive value. Interestingly, the voltage output shows a dramatic nonlinear response which may be useful for the voltage diode application with a push-pull input voltage. In addition, the heat fluxes of the asymmetric input are much smaller than those of the symmetric input. The maximum value of the heat flux under the symmetric input exceeds twice of that under the asymmetric input. Our results are useful to design nanoelectronic devices based on α−T 3 TBJ.

Three-terminal ballistic junction based on phosphorene

We investigate nonlinear electric response of a phosphorene-based three-terminal ballistic junction (TBJ) where two terminals (‘ l’ and ‘ r’) are armchair nanoribbons and the other (‘ m’) is a zigzag ribbon. The transmission among leads is found to be strongly anisotropic. When the push–pull voltage is applied on the terminal ‘ l’ and ‘ m’ (), the output voltage exhibits a remarkable change of slope () from one side of its extremum point to the other. The heat flux in the input terminals is much smaller than that for the conventional symmetric-input configuration with . As one armchair terminal is grounded, the output voltage from the other armchair terminal exhibits a typical voltage diode feature. The voltage transistor function is demonstrated, whose response parameters depend on the choice of output terminals. We also examine the phosphorene TBJ with two zigzag terminals and one armchair terminal, whose voltage response in all cases is similar to conventional TBJs due to a weak transmission anisotropy. The heat flux in the TBJ transistor depends on the edge type and width of leads. Its amplitude under the symmetric-input configuration exceeds twice of that under the asymmetric-input configuration. These results reveal unique advantages of phosphorene-based TBJ for nanoelectronic applications.

Nanoscale Simulation of Three-Contact Graphene Ballistic Junctions

In this work, three-terminal ballistic junctions, made of three-branch graphene nanoribbons (GNRs), are considered and simulated at the nanometric scale. The analysis is carried out by a scattering matrix approach, in a discrete formulation optimized for GNR devices. The ballisticity and the scattering properties of the junction contribute to the nonlinear behaviour, as, in fact, a sinusoidal voltage between two GNR branches results in a non-sinusoidal current at the third branch. The input-output characteristic is hardly predictable at the nanoscale, as it depends on several cooperating factors, namely the potential distribution and the geometry of the junction. Several numerical examples are shown to illustrate the above concepts.

Nonlinear electrical properties of Si three-terminal junction devices

This letter reports on the realization and characterization of silicon three-terminal junction devices made in a silicon-on-insulator wafer. Room temperature electrical measurements show that the fabricated devices exhibit pronounced nonlinear electrical properties inherent to ballistic electron transport in a three-terminal ballistic junction (TBJ) device. The results show that room temperature functional TBJ devices can be realized in a semiconductor material other than high-mobility III-V semiconductor heterostructures and provide a simple design principle for compact silicon devices in nanoelectronics.

Linear and Non-Linear Response in T-Shaped Electron Waveguides

Recent experimental results on three-terminal ballistic junction (TBJ) [1] showed their interesting electron transport properties as candidates for effective logic gates for quantum computing [2]. A similar device was proposed by Baranger [3] where T-shaped ballistic junction and four-terminal devices were examined. It was shown that oscillatory behavior of transmission coefficients can be explained accurately by bend resistance and threshold effect. In addition for specific parameters he observed appearance of the Wigner cusp [4] in transmission coefficients. In this paper we will show that the Wigner singularities can be observed in measurable quantities, such as conductance and voltage.

Transport properties of three-terminal ballistic junctions realized by focused ion beam enhanced etching in InGaAs/InP

Three-terminal junction devices are realized in an InGaAs/InP quantum well by focused ion beam (FIB) implantation and selective wet etching. Room temperature electrical measurements show that the fabricated devices exhibit strong nonlinear electrical properties. The results are discussed in terms of ballistic electron transport. It is demonstrated that FIB-enhanced etching processing can be exploited as a maskless, resist-free technique for fabrication of high-quality and functional nanoelectronic devices.

A Novel SR Latch Device Realized by Integration of Three-Terminal Ballistic Junctions in InGaAs/InP

In this letter, a novel sequential logic device based on three-terminal ballistic junctions (TBJs) is proposed and demonstrated. Two TBJs and two in-plane gates are laterally integrated in a high-electron-mobility InGaAs/InP quantum-well material by a single-step lithography process. Electrical measurements reveal that the integrated device functions as a set-reset (SR) latch with voltage gains at room temperature. The demonstrated device provides a new and simple circuit design for SR latches in digital electronics.

Novel room-temperature functional analogue and digital nanoelectronic circuits based on three-terminal ballistic junctions and planar quantum-wire transistors

Three-Terminal ballistic junctions (TBJs) and planar quantum-wire transistors (QWTs) are emerging nanoelectronic devices with various novel electrical properties. In this work, we realize novel nanoelectronic analogue and digital circuits with TBJs and planar QWTs made on In0.75Ga0.25As/InP two-dimensional electron gas (2DEG) material. First we show that a single TBJ can work as a frequency mixer or a phase detector. Second, we fabricate an integrated nanostructure containing two planar QWTs, which can be used as an RS flip-flop element. Third, we make a nanoelectronic circuit by the integration of two TBJs and two planar QWTs. This circuit shows the RS flip-flop functionalities with much larger noise margins in both high and low level inputs. All measurements in this work are done at room temperature.

Nonlinear electron transport in InAs/AlGaSb three-terminal ballistic junctions

We have fabricated and characterized an InAs/AlGaSb three-terminal ballistic junction device. The fabricated device exhibited nonlinear electron transport properties because of ballistic motion of electrons in this structure that is comparable to the electron mean free path. When the left branch is biased to a finite voltage Vand the right to a voltage of -V (push-pull fashion), negative voltages appeared at the floating central branch regardless of the polarity of the input voltages. In the case of the central branch grounded in push-pull fashion, the clear current rectification effect also observed in the current flow of the central branch at 4.2K to even at 300K.

Ballistic nanodevices for high frequency applications

We report on the study of devices exploiting ballistic transport at room temperature by means of simulations and experimental results. Ballistic effects have been demonstrated at room temperature since a few years. This paper presents the work realised since 2001 on ballistic nanodevices at the Institut d'Electronique, Microelectronique et Nanotechnologie (IEMN). We will present the fabrication process and the characterisation of ballistic devices. We work on InGaAs-based devices optimised for ballistic transport, where the electron mean free path can reach around 130-160 nm at room temperature in channels with high indium content. We show that nanostructures around this size can be fabricated with the help of modem lithography techniques and are compatible with InP-HEMT technology. Devices under scope are Three-terminal Ballistic Junctions (TBJ) and their typical application is rectification. We have also characterised ballistic rectifiers up to 94 GHz. Measurements were realised on two TBJs integrated in parallel in a coplanar waveguide. We also show the frequency doubling characteristic of a single TBJ at 600 MHz.

Frequency mixing and phase detection functionalities of three-terminal ballisticjunctions

Three-terminal ballistic junctions (TBJs) are fabricated from a high-mobilityInP/In0.75Ga0.25As heterostructure by electron-beam lithography. The voltage output from the central branchis measured as a function of the voltages applied to the left and right branches of the TBJs.The measurements show that the TBJs possess an intrinsic nonlinearity. Based on thisnonlinearity, a novel room-temperature functional frequency mixer and phase detectorare realized. The TBJ frequency mixer and phase detector are expected to haveadvantages over traditional circuits in terms of simple structure, small size andhigh speed, and can be used as a new type of building block in nanoelectronics.

Ballistic nano-devices for high frequency applications

In this paper, we present a study on three-terminal ballistic junction and their applications to rectifiers and MUX/DEMUX. Rectifying effect is observed up to 94 GHz at room temperature. Although THz frequency performance has been demonstrated by Monte Carlo simulation, the high impedance of the nano-device combined with the parasitic capacitances is a limiting factor.

Nonlinear electrical properties of three-terminal junctions

The authors report on room-temperature electrical measurements of three-terminal junctions made from a semiconductor heterostructure. The correlation between the junction size of the devices and the voltages needed to be applied in order to observe the electrical characteristics of three-terminal ballistic junctions is studied. The authors show that the ballistic behavior of electron transport can be observed in a three-terminal junction with a junction size of a few micrometers, much larger than the mean free path of electrons in the material. The results are explained in terms of a bias-induced enhancement of the electron mean free path in the system.

ANALYSIS OF BANDWIDTH AND NONLINEAR EFFECTS IN InGaAs-BASED BALLISTIC NANODEVICES FOR APPLICATIONS UP TO THz RANGE

Analysis of nonlinear effects in InAlAs/InGaAs -based channels and three-terminal ballistic junctions (TBJs) is performed for applications up to THz range. Results show that InGaAs -based channels designed for ballistic operation exhibit high intrinsic cut-off frequency (fT ~ 10 THz ). Nonlinear effects in TBJs, which result from device geometry and space charge distribution, show good qualitative agreement with published results.

Novel Nanoelectronic Triodes and Logic Devices With TBJs

In this letter, we demonstrate the realization of novel diodes, triodes, and logic gates with three-terminal ballistic junctions (TBJs) made from a semiconductor heterostructure. The approach exploits the ballistic nature of electron transport, which has emerged in the nanostructures. Importantly, we show that TBJs function as logic AND gates and can be used to construct other compound logic gates, such as NAND gates with voltage gain, when combined with a point contact (an inverter). The demonstrated devices show favorable characteristics such as low turn-on voltage in rectification and room-temperature operation.

Tunable nonlinear current–voltage characteristics of three-terminal ballistic nanojunctions

The current–voltage (I–V) characteristics of three-terminal ballistic junctions (TBJs) fabricated from high-electron-mobility GaInAs/InP quantum-well structures are measured in the six-terminal configuration. These characteristics show strong nonlinear, diode-like behavior, in agreement with recent theoretical calculations. Furthermore, the I–V characteristics are tunable by the voltage applied directly to one branch of the TBJs acting as a gate. An additional tuning of the characteristics of the TBJ devices can be performed using an in-plane side gate. All the presented characteristics are measured at room temperature, which makes TBJ devices promising for future nanoelectronic applications.

Quantum effects in the transport properties of nanoelectronic three-terminal Y-junction devices

We report on a theoretical study of the electrical properties of three-terminal ballistic junction (TBJ) devices, consisting of three perfect leads and a ballistic coupling region, using a multiterminal scattering-matrix approach and the Landauer-B\"uttiker transport theory. The calculations have been performed for TBJ devices with different structure properties, at both high and low temperatures, as well as at both small and large applied bias voltages. The study is focused on the effects of quantum scattering, which is treated by exact numerical calculations. It is shown that when operated in the push-pull fashion, i.e., by applying finite voltages ${V}_{l}=V$ and ${V}_{r}=\ensuremath{-}V$ to the left and right branches, the TBJ devices exhibit strong nonlinearities in the output voltage ${V}_{c}$ calculated at the central branch. At high temperatures, the output voltage ${V}_{c}$ as a function of V shows the same nonlinear characteristics as observed in recent theoretical analyses and experimental measurements. These high-temperature electrical characteristics are found to be qualitatively insensitive to the structure details of the devices and reveal little effect of quantum scattering. At low temperatures, the output voltage ${V}_{c}$ shows fluctuations, and can assume either negative or positive values, depending on the chemical potential, at small bias regions. These behaviors are explained in terms of the fluctuations seen in the transmissions between the terminals, while the transmission fluctuations are shown to arise from strong scattering by quasibound states formed in the junction cavity region and are therefore signatures of quantum effects. Based on the quantum fluctuation nature of the device characteristics, a single multilogic device, constructed with a single TBJ, with switching of the logic functions by means of a gate, is proposed.

Nanoimprint technology for fabrication of three-terminal ballistic junction devices in GaInAs/InP

We present processing technology based on nanoimprint lithography (NIL) and wet etching for fabrication of GaInAs/InP three-terminal ballistic junction (TBJ) devices. To transfer sub-100 nm features into a high-mobility InP-based 2DEG material, we used SiO 2/Si stamps made with electron beam lithography and reactive ion etching. After the NIL, the resist residues are removed in oxygen plasma followed by wet etching of GaInAs/InP to define the TBJ-structures. Fabricated TBJ-devices are characterized using scanning electron microscopy and electron transport measurements. Highly non-linear electrical characteristics of the TBJ structures are demonstrated and compared with E-beam defined devices.

Scattering-matrix formalism of electron transport through three-terminalquantum structures: formulation and application to Y-junction devices

In this paper we present a formalism for the calculation of electron transportthrough three-terminal junction devices, which have received attentiondue to their recently demonstrated non-linear electrical properties. Theformalism, which is based on the scattering-matrix method, takes quantuminterference effects fully into account. Furthermore, the formalism providesnumerical stability in the calculations as well as large flexibility in themodelling of arbitrary potential profiles due to the common basis approachused in the formulation. The method is used to calculate the transportproperties for Y-shaped three-terminal ballistic junction (TBJ) structures withconfigurations typical of recently performed experiments. Quantum interferenceeffects are shown to strongly influence the transport characteristics of TBJstructures due to complex scattering of the electrons in the cavity-like couplingwindow between the three arms of the device. The theoretical approachpresented in this paper provides a flexible tool for the study of such quantuminterference effects, which may play an important role in the design andfunctionality of future nanoscale devices based on three-terminal junctions.

Nanoimprint lithography for fabrication of three-terminal ballistic junctions inInP/GaInAs

We present processing technology and characterization results for InP/GaInAstwo-dimensional electron gas (2DEG) three-terminal ballistic junction (TBJ)devices manufactured using nanoimprint lithography (NIL). To transfer sub-100nm features into a high-mobility InP-based 2DEG material, we used SiO2/Sistamps made using electron beam lithography and reactive ion etching. After NIL,the resist residues are removed in oxygen plasma; this is followed by wet etchingof InP/GaInAs to define the TBJ structures. Fabricated TBJ devices arecharacterized using scanning electron microscopy and electron transportmeasurements. Highly non-linear electrical characteristics as predicted bythe theory (Xu H Q 2001 Appl. Phys. Lett. 78 2064) are demonstrated.