Quantum steering of electron wave function in an InAs Y-branch switch

Abstract

We report experimental results on gated Y-branch switches made from InAs ballistic electron waveguides. We demonstrate that gating modifies the electron wave functions as well as their interference pattern, resulting in anticorrelated oscillatory transconductances. Our data provide evidence of steering the electron wave function in a multichannel transistor structure. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1867554͔ Quantum effects in nanostructures provide insights into fundamental issues that cannot be addressed in atomic physics settings and offer perspectives for future applications in computing. 1 In the regime where quantum effects dominate, electron transport exhibits different properties. For example, when the device size becomes less than the elastic mean-free path, electrons can traverse through the conductor ballistically, leading to conductance quantization. In addition, phase coherent transport plays an important role in nanometer-scale devices. Among devices exploiting these quantum effects, the Y-channel transistor is attractive on its own right. The original proposal of the Y-channel transistor, or Y-branch switch ͑YBS͒ ͑Ref. 2͒ came from an electron wave analogy to the fiber optic coupler. The semiconductor version of YBS has a narrow electron waveguide patterned into a "Y" configuration with one source and two drain terminals. A lateral electric field perpendicular to the direction of electric current in the source waveguide steers the injected electron wave into either of the two outputs. YBS offers several advantages as a fast switch as evidenced by THz ͑Refs. 3 and 4͒ operation of quantum point contacts ͑QPC͒. Most interestingly, in the case of single mode occupation, the switching can be accomplished by a voltage of the order of ប͑e t ͒, where t is the transit time of electrons. 5 With a proper design, the switching voltage for a YBS can become smaller than the thermal voltage, k B T / e, as opposed to 40-80 times of k B T / e needed for the current transistors. Here, k B is the Boltzmann constant and T is the absolute temperature. Switching at low voltages would make such devices less noisy and consume less power, though at the expense of speed. 6

Acoustoelectric Y-branch switch

“…We note that the potential of electronic switching in mesoscopic devices for signal processing purposes has been recognized long ago and the ballistic Y-branch switch has been studied intensively both theoretically and experimentally. [10][11][12][13][14] The wafer for this study was grown on a ͑100͒ semiinsulating GaAs substrate and consists of a 200 nm GaAs buffer, followed by 20 periods of an AlGaAs/ GaAs GaAs superlattice ͑2.5 nm AlGaAs and 2.5 nm GaAs constitute the period͒, 50 nm Al 0.33 Ga 0.67 As, 30 nm GaAs QW, 40 nm Al 0.33 Ga 0.67 As spacer, 40 nm Al 0.33 Ga 0.67 As layer doped with 5 ϫ 10 17 cm −3 of Si, and a 10 nm GaAs cap layer. The level of the doping was chosen to partially satisfy the surface states but to leave the QW free of electrons.…”

Nonlinear electron transport properties and rectification effects in InAs/AlGaSb ballistic devices

“…In these reports, the devices were fabricated either on GaAs/AlGaAs heterostructures [5,11] or InGaAs-based heterostructures [4,6,[7][8][9]12]. As for InAs related materials, it has been reported that the electron wave function in the InAs/AlSb Y-branch structures was steered in the state kept near equilibrium [13].…”

Performance optimization of room temperature Deflection Transistors through modified geometry

“…It is known that at such a small scale the wave like nature of the electron comes into picture and the gating causes the quantum effects to occur. The gating modifies the electron wave functions and their interference pattern, which results in anticorrelated oscillatory transconductance [7].…”