3-terminal Device Research Articles

Robust, versatile, direct low-frequency noise characterization method for material/process quality control using cross-shaped 4-terminal devices

Low frequency (LF) noise measurement is a very sensitive tool for device quality and reliability monitoring. Despite of its potential interest, there are up to now relatively few LF noise studies combined and compared to standard reliability/quality analysis. One of the reasons is the difficulty to implement LF noise measurement on automatic wafer level testing. In this paper we promote a method using cross shaped 4 terminal devices (Hall crosses). The implementation of this method and its advantages over conventional noise measurement methods are described. This method, compatible with on-wafer probe testing, is of particular interest for material/processes quality control purposes especially for less mature material such as AlGaN/GaN Heterostructures.

Three-terminal organic memory devices

An organic electrical bistable device (OBD) has been reported previously, which has an organic∕metal-nanocluster∕organic structure sandwiched between a top and bottom electrode [L. P. Ma, J. Liu, and Y. Yang, Appl. Phys. Lett. 80, 2997 (2002)]. This device can be switched between a low- (OFF) and a high- (ON) conductivity state by external bias. In this article, we report a three-terminal organic memory device, which is realized by wiring out the metal-nanocluster layer of the OBD as the middle electrode. The ON and OFF states of the device can be read out by measuring the potential of the middle electrode. By controlling the interface formation of the device, a three-terminal OBD with a potential change on the middle electrode of more than three orders in magnitude between the OFF state and ON state (from 0.2mVto0.77V) is achieved. By wiring out the middle electrode, the three-terminal OBD can also be considered as two 2-terminal devices stacked together. By proper interface engineering (to be discussed in detail in the text), we found that both the top and bottom devices show electrical bistability and memory effect. This can double the data storage density of the memory device. Details of the device mechanism are provided.

Circuit model for domain walls in ferromagnetic nanowires: Application to conductance and spin transfer torques

We present a circuit model to describe the electron transport through a domain wall in a ferromagnetic nanowire. The domain wall is treated as a coherent 4-terminal device with incoming and outgoing channels of spin up and down and the spin-dependent scattering in the vicinity of the wall is modelled using classical resistances. We derive the conductance of the circuit in terms of general conductance parameters for a domain wall. We then calculate these conductance parameters for the case of ballistic transport through the domain wall, and obtain a simple formula for the domain wall magnetoresistance which gives a result consistent with recent experiments. The spin transfer torque exerted on a domain wall by a spin-polarized current is calculated using the circuit model and an estimate of the speed of the resulting wall motion is made.

Observation of a controllableπjunction in a 3-terminal Josephson device

Recently Baselmans et al. [Nature, 397, 43 (1999)] showed that the direction of the supercurrent in a superconductor/normal/superconductor Josephson junction can be reversed by applying, perpendicularly to the supercurrent, a sufficiently large control current between two normal reservoirs. The novel behavior of their 4-terminal device (called a controllable PI-junction) arises from the nonequilibrium electron energy distribution established in the normal wire between the two superconductors. We have observed a similar supercurrent reversal in a 3-terminal device, where the control current passes from a single normal reservoir into the two superconductors. We show theoretically that this behavior, although intuitively less obvious, arises from the same nonequilibrium physics present in the 4-terminal device. Moreover, we argue that the amplitude of the PI-state critical current should be at least as large in the 3-terminal device as in a comparable 4-terminal device.

Spin-transport in multi-terminal normal metal-ferromagnet systems with non-collinear magnetizations

A theory of spin-transport in hybrid normal metal - ferromagnetic electronic circuits is developed, taking into account non-collinear spin-accumulation. Spin-transport through resistive elements is described by 4 conductance parameters. Microscopic expression for these conductances are derived in terms of scattering matrices and explicitly calculated for simple models. The circuit theory is applied to 2-terminal and 3-terminal devices attached to ferromagnetic reservoirs.

Nanoscale SNS junction fabrication in superconductor-normal metal bilayers

We have developed a reliable and versatile technique for fabricating SNS junctions in a superconductor-normal metal bilayer using a focused ion beam microscope (FIB) in conjunction with an in-situ resistance measurement technique. This technique offers a simple method for creating multi-junction devices (SQUIDs, 3-terminal devices, arrays) with high integration densities. In this paper we discuss recent results from devices created in Nb-Cu tracks by cutting 50 nm trenches in the top Nb layer to weaken the superconducting coupling. Cuts of depths between 60 and 100% of the Nb thickness yield reproducible junctions with current voltage (I(V)) characteristics in accordance with the resistively-shunted-junction (RSJ) model, characteristic voltage I/sub C/R/sub N//spl sim/50 /spl mu/V at 4.2 K and excellent microwave response. A thorough study has been carried out of the effect on device parameters of varying the Cu layer thickness (0-175 nm). In addition transmission electron microscopy (TEM) studies have been carried out on the device structure. A two-channel model of device operation has been developed and related to the results of I/sup C/R/sub N/(T) measurements (down to 350 mK) on selected devices.

Quasi-particle injection devices for interfaces between superconductors and semiconductors

We have fabricated an injection type 3-terminal device for interface between superconductor and semiconductor circuits using a high temperature superconductor. When quasi-particles are injected from the Au electrode to a YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) bridge, superconductivity of the bridge area is weakened and I/sub c/ of the bridge decreases. Therefore, we can easily make the bridge in resistive state by injecting sufficient amount of current I/sub inj/. The length, width, and thickness of the bridge are 20 /spl mu/m, 10 /spl mu/m, and 100 nm, respectively. The Au-YBCO contact area is 200 /spl mu/m/sup 2/. When the bridge became resistive, the resistance was about 100 /spl Omega/. The current gain |/spl Delta/I/sub c///spl Delta/I/sub inj|/ was as high as 9. However, the contact resistance was about 17 /spl Omega/, which is 200 times as large as the required value for the operation as an interface device. This shortcoming might be overcome by appropriate annealing.

NON-EQUILIBRIUM IN JOSEPHSON JUNCTIONS: POSSIBLE TRANSISTOR-LIKE APPLICATIONS

Interest in superconducting transistors is due to some potential benefits of these devices, such as the possibility to have large current gain and bandwidth at low temperatures. In this work we present experimental results concerning with a new superconducting 3-terminal device showing true transistor-like properties at T=4.2K. It is a stacked double tunnel junction structure where the intermediate film is a bilayer of superconducting Nb with an Al quasiparticle trap which can be either in the superconducting or in the normal metal state. Current amplification factors of up to 2.0 are observed at a temperature of 4.2 K when the Al is superconducting. When the Al is in the normal state, large current gains of more than 50 are observed. The operation is highly directional, i.e. practically no effect is observed when the roles of the injector and detector junctions are reversed. The results are explained according to the recently proposed QUAsiparticle TRApping TRANnsistor model.

Design of an Indegenised Negative Resistance Characteristics Curve Tracer

“Negative Resistance” exhibited by a device during some portion of its V‐I characteristics produces jump phenomenon, hysteresis and oscillation in the tracing circuitry. A method is presented to overcome the above problems in tracing the negative resistance characteristics of 2‐terminal and 3‐terminal devices by an indeginised curve plotter.

A Potential Interconnection Method in Molecular Electronics

AbstractA method to electrically connect molecular devices is proposed, which has the potential to develop into an interconnection technology for 3-dimensional molecular electronic circuits. The method is based on electric-bias-induced polarization and electric-pulse-induced chemical reactions. Two molecules to be connected are oppositely biased to induce opposite charges in them. The opposite charges will create electrostatic attraction that pulls together or aligns the two molecules. An electric pulse is then applied across the two molecules to trigger a chemical linking reaction between them. The electric pulse overcomes the activation energy for such a reaction. Chemical linking reactions to produce conjugated molecular chains are proposed for several conjugated molecules, such as phenylene, ethylene, and acetylene based molecules, with different end groups, such as phenyl and acetyl groups. Applications of this method in assembling 3-terminal molecular devices and 3-dimesional molecular electronic circuits are speculated. Major challenges in realizing this interconnection method are also outlined.

A Novel Four Terminal Poly-Si Tft Suppressing Kink and Improving Reliability

ABSTRACTWe fabricated a new device, which employs counter-doped lateral body terminal (CLBT) in order to suppress kink effects and improve the device stability. Proposed device also employs a buried channel (BC), which increases ON-current and operating frequency. Although LDD structure is not employed in the proposed device, low OFF-current is successfully obtained due to elimination of minority carrier through CLBT. We have measured the dynamic properties of poly-Si TFT device and circuit. The reliability of TFT and circuits after AC stress is also discussed in our paper.The proposed poly-Si TFT has high ON-current and low OFF-current compared with conventional 3-terminal poly-Si TFT. The 4-terminal device characteristics were measured with source and CLBT shorted. The proposed device exhibits superior performance to conventional device in ON-current because BC prevents carrier scattering to gate oxide. We have performed bias and high temperature stress test of ring oscillator in order to investigate dynamic reliability between conventional poly-Si TFT and proposed 4-terminal poly-Si TFT. Our experimental results show that BC enables the device to have high mobility and switching frequency (33MHz at VDD=15V). The minority carrier elimination of CLBT suppresses kink effects and makes superb dynamic reliability of CMOS circuit.

Development of high-quantum-efficiency, lattice-mismatched, 1.0-eV GaInAs solar cells

High-quantum-efficiency, lattice-mismatched, 1.0-eV GaInAs solar cells grown by organometallic vapor phase epitaxy have been developed for ultimate integration into AlGaAs/GaAs/GaInAs 3-junction, 2-terminal monolithic devices. The more standard n/p junction was replaced with an n-i-p structure in the GaInAs cell in order to increase the short-circuit current by overcoming the material deficiencies which arise as a result of accommodating the lattice mismatch. This led to single junction 1.0-eV GaInAs cells with internal quantum efficiencies >90% and short-circuit-current densities that match or closely approach those needed to current match the upper AlGaAs and GaAs cells. A 4.1% (1-sun, air mass 0,25°C) power conversion efficiency was achieved with a developmental structure, indicating the potential of the lattice-mismatched n-i-p 1.0-eV GaInAs cell. An analogous device designed to allow direct monolithic integration with the upper AlGaAs and GaAs cells, with a modified grading layer of AlGaInAs in place of the usual GaInAs, achieved an efficiency of 2.2%, primarily due to a lower open-circuit voltage. The open-circuit voltage is perhaps limited by structural defects revealed in transmission electron micrographs.

A study of resonant tunneling in a 3-terminal ballistic device

Preliminary results are presented for a 3-terminal device fabricated by incorporating a narrow quantum well into the collector barrier of a unipolar hot electron transistor. The structure allows unique studies of the mechanism of resonant tunneling in which the carrier injection energy and the bias across the double barrier can be independently varied. The transistor clearly shows an additional current collection threshold representing as much as 10% of the injected current attributable to tunneling via the single subband in the quantum well. This interpretation is confirmed by measurements in perpendicular and parallel magnetic fields despite the fact that theoretical estimates of the resonant tunneling current without scattering are many orders of magnitude smaller, and there are strong indications that elastic scattering in the well is responsible for the enormous discrepancy. The data tend to support proposals (Guéret, 1989a, 1989b; Wolak, 1988) that elastic scattering is responsible for the large valley currents in resonant tunneling diodes, and it appears that the tunnel process may not be completely incoherent as has frequently been assumed up to now.

Effects of the third-electrode positions on three-terminal GaAs p+n-δ(p+)n-n+ switching devices

GaAs p+n- δ(p+)n-n+ 3-terminal switching devices prepared by molecular beam epitaxy are fabricated. The positions of the third electrode are found to affect the device characteristics profoundly. The effects of 3rd-electrode positions with bias conditions are investigated in the paper. Control efficiency is then defined to compare the device performance.

Negative resistance curve tracer

Tracing the negative resistance characteristics of 2-terminal and 3-terminal devices often ended in failure due to jump phenomenon, hysteresis, and oscillation resulting from the tracing circuit. All of these problems are overcome in the curve tracer described in this paper. A detailed nonlinear dynamic circuit analysis is used to develop a simple method for quenching oscillations and other exotic phenomena. Our curve tracer is designed to trace either voltage-controlled or current-controlled negative resistance characteristics of both 2-terninal and 3-terminal devices. All six representations which completely characterized a 3-terminal or 2-port nonlinear resistor are allowed. In particular, using a novel approach for implementing a nullator and norator, transmission (chain) characteristics of 3-terminal and 2-port devices have been successfully traced for the first time.

Physical frequency limitations of 2-terminal devices

The usual causes of power limitations for microwave 2-terminal devices are first analysed; other physical limitations, which assume particular importance in the millimetre-wave range, are then systematically studied. The influence of the nonstationary effects of electron dynamics on the behaviour of millimetre 2-terminal devices is summarised. For this purpose, several recent theoretical models are described.

New semiconductor active device: the conductivity-controlled transistor

A new semiconductor 3-terminal device has been realised in which a majority-carrier current, flowing in a N+-N-N+ structure, is controlled by a minority-carrier current supplied by a forward-biased P+-N junction. The properties of this device are presented and discussed in terms of a physical model.

New avalanche-injection-controlled switch

A new 3-terminal switching device, based on the avalanche-injection effect, is proposed. Its working principle is confirmed both by theoretical and experimental results. Experimental switching times of the order of a nanosecond have been observed.

Amplification with 3-terminal avalanche devices

The letter investigates the influence of a thermionic-type injected current on the dynamic operating conditions and performance of GaAs impatt diodes. For this study, the computer program developed for high-efficiency impatt diodes has been used extensively. The work shows that interesting results can be obtained in X-band and that the practical realisation of such a device would be possible by using a transistor in which the transistor effect, avalanche effect and transit-time effect are used in combination.

Novel 3-terminal amorphous-semiconductor device

A 3-terminal device containing an amorphous chalcogenide semiconductor is described. It is shown that, with the application of relatively low voltage pulses of appropriate polarity to a control electrode, switching of the device can be initiated or prevented.