Feasibility of hybrid Josephson field effect transistors

Clark, T. D.; Prance, R. J.; Grassie, A. D. C.

doi:10.1063/1.327935

Cited by 158 publications

(75 citation statements)

References 22 publications

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“…We emphasize that the observation and control of such a robust Josephson effect is made possible by the chosen device architecture, which allows us to use short SNS junctions while retaining full tunability of the supercurrent flow. In fact there is no fundamental lower limit to L in our scheme, while other approaches such as, for instance, Josephson field effect transistors (JoFETs) [10,26,27], require longer junctions to allow electrostatic gating and avoid excessive screening from the electrodes. These requirements lead to larger control voltages, weaker proximity effect and stray capacitance dictated by the integration of strongly-coupled gates on top of short junctions.…”

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confidence: 99%

Hot-electron effects in InAs nanowire Josephson junctions

et al. 2010

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At a superconductor (S)-normal metal (N) junction pairing correlations can "leak-out" into the N region. This proximity effect [1,2] modifies the system transport properties and can lead to supercurrent flow in SNS junctions [3]. Recent experimental works showed the potential of semiconductor nanowires (NWs) as building blocks for nanometre-scale devices [4][5][6][7], also in combination with superconducting elements [8][9][10][11][12]. Here, we demonstrate an InAs NW Josephson transistor where supercurrent is controlled by hot-quasiparticle injection from normal-metal electrodes. Operational principle is based on the modification of NW electron-energy distribution [13][14][15][16][17][18][19][20] that can yield reduced dissipation and high-switching speed. We shall argue that exploitation of this principle with heterostructured semiconductor NWs opens the way to a host of out-of-equilibrium hybrid-nanodevice concepts [7,21].One practical implementation of the present InAs-NW hot-electron Josephson transistor concept is shown in Figure 1a. The SNS junction was fabricated by e-beam lithography starting from an n-doped InAs NW (the N region, for further details see Methods) and comprises two Ti/Al superconducting electrodes placed at a distance L ≃ 60 nm (S regions). Control electrodes were fabricated by depositing two additional normal-metal Ti/Au leads at the two ends of the NW. As schematically illustrated by the overlay of Fig. 1a, the N leads are used to drive a dissipative current through the NW thereby tuning Josephson coupling in the S-NW-S structure. Figure 2a shows a set of typical IV characteristics from one of the measured S-NW-S junctions at equilibrium (i.e., V inj = 0) and at different bath temperatures T . High critical currents up to I c ≃ 350 nA (corresponding to a supercurrent density ∼ 5.5 kA/cm 2 ) are observed and Josephson coupling typically persists up to about 1 K. Furthermore, from the junction differentialresistance spectra (see Supplementary Materials) we infer a superconducting order parameter ∆ = 120 µeV and a junction normal-state resistance R N ≃ 210 Ω. The I c R N product attains values as large as ≃ 75 µeV and indicates the overall success of our junction-fabrication procedure [22]. Based on carrier-density and electronmobility values (see Methods) we estimate a momentumrelaxation length ℓ ≃ 20 nm and a diffusion coefficient D = 0.02 m 2 /s. Given the junctions geometrical length L we can estimate the Thouless-energy value, i.e., the characteristic energy scale of the N region, E Th = D/L 2 ≃ 4 meV. These values indicate that our devices can be described within the frame of the diffusive short-junction limit (L > ℓ and ∆ ≪ E Th ) [22]. Figure 2b shows the evolution of I c versus T at V inj = 0 for two representative devices D1 and D2. For comparison, the theoretical prediction for an ideal short diffusive SNS junction [22,23] is also plotted assuming for both devices a supercurrent suppression of the order of 45%. Such a suppression can be expected and probably mainly stems from a...

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Hot-electron effects in InAs nanowire Josephson junctions

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Much of that interest was stimulated by the 1978/1980 papers of Silver et al 17 and Clark et al, 18 who proposed three-terminal gate-modulatable weak-link devices, referred to as hybrid Josephson field effect transistors, or briefly JOFETs. These devices draw on the ability to modulate the electron concentration in a thin semiconductor layer via a gate electrode, and thereby modulate the Josephson critical current.…”

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Current-voltage characteristics of semiconductor-coupled superconducting weak links with large electrode separations

et al. 1998

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We have studied the current-voltage characteristics of superconducting weak links in which the coupling medium is the 2-D electron gas in InAs-based semiconductor quantum wells, with relatively large (typically 0.5µm) separations between niobium electrodes. The devices exhibit Josephson-like current-voltage characteristics; however, the falloff of the differential resistance with decreasing temperature is thermally activated, and is orders of magnitude slower than for more conventional weak links. Most unexpectedly, the thermal activation energies are found to be proportional to the width of the device, taken perpendicular to the current flow. This behavior falls outside the range of established theories; we propose that it is a fluctuation effect caused by giant shot noise associated with multiple Andreev reflections. The possibility of non-equilibrium effects is discussed.

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“…Especially the control of the supercurrent in a weak-link structure has attracted considerable interest in recent years. 1 One approach was to transfer the well-known semiconductor field effect transistor to superconductor/two-dimensional electron gas ͑2DEG͒ structures as proposed by Clark et al 2 The supercurrrent flowing through the 2DEG was switched off by reducing the coherence length in the channel by applying a negative gate voltage. 3,4 Since the voltage necessary for depleting the electrons in the 2DEG channel is typically of the order of the band gap of the semiconductor and the output signal of the order of the superconducting gap of the electrodes, a voltage gain is hard to achieve.…”

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Local suppression of Josephson currents in niobium/two-dimensional electron gas/niobium structures by an injection current

et al. 1999

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We investigated niobium-AlGaSb/InAs-niobium hybrid structures using a high mobility two-dimensional electron gas as a weak link. The Josephson current observed in this structure was suppressed by an injection current driven into the weak link via an additional normal lead. Using a four-terminal configuration the supercurrent is suppressed all over the weak link. In a three-terminal configuration it was possible to suppress the supercurrent locally. ͓S0163-1829͑99͒06217-7͔The semiconductor/superconductor hybrid structure has been the subject of extensive research during the last years, to prove its suitableness as an interface between superconductor and semiconductor electronics. Especially the control of the supercurrent in a weak-link structure has attracted considerable interest in recent years. 1 One approach was to transfer the well-known semiconductor field effect transistor to superconductor/two-dimensional electron gas ͑2DEG͒ structures as proposed by Clark et al. 2 The supercurrrent flowing through the 2DEG was switched off by reducing the coherence length in the channel by applying a negative gate voltage. 3,4 Since the voltage necessary for depleting the electrons in the 2DEG channel is typically of the order of the band gap of the semiconductor and the output signal of the order of the superconducting gap of the electrodes, a voltage gain is hard to achieve. An alternative concept to avoid this problem is controlling the supercurrent by the injection of electrons via an additional nonsuperconductive contact into the weak link. [5][6][7][8] The energy of these carriers should be only of the order of the superconducting gap of the electrodes. Very recently, the control of the supercurrent by an injection current was experimentally succeeded for a Nb/Au weak link structure. 9 This system was in the diffusive regime with inelastic scattering processes thermalizing the injected carriers.In our current-controlled structure the superconductor Nb was contacted to a high-mobility two-dimensional electron gas ͑2DEG͒ in an Al 0.2 Ga 0.8 Sb/InAs heterostructure. Due to the high electron mobility the carrier transport from one Nb electrode to the opposite one can be considered to be ballistic. In addition inelastic scattering should become relevant only for higher temperatures. For weak links without inelastic scattering an even more efficient tuning of the Josephson current was predicted compared with the case of inelastic scattering present. 10 It will be shown that if a current is injected via Ohmic contacts into the 2DEG in a four-terminal configuration the supercurrent can be suppressed completely. In a three-terminal configuration it was possible to suppress the supercurrent locally, which was proven by measuring and fitting the interference patterns of the Josephson current appearing when a magnetic field is applied to the weak link.The heterostructure which forms the weak link in our structure was grown by molecular-beam epitaxy on a semiinsulating GaAs substrate. After a 1100 nm Al-Ga-Sb buffer layer, a 5...

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Feasibility of hybrid Josephson field effect transistors

Cited by 158 publications

References 22 publications

Hot-electron effects in InAs nanowire Josephson junctions

Hot-electron effects in InAs nanowire Josephson junctions

Current-voltage characteristics of semiconductor-coupled superconducting weak links with large electrode separations

Local suppression of Josephson currents in niobium/two-dimensional electron gas/niobium structures by an injection current

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