Dutch scientists build nanoscale superconducting transistor
Scientists from the Kavli Institute of Nanoscience at Delft, The Netherlands and Philips Research have developed superconducting transistors based on semiconducting nanometer-scale indium arsenide wires, Philips said early this week (July 4).
The devices enable the fabrication of novel nanoscale superconducting electronic circuits and at the same time they provide opportunities for the study of fundamental quantum transport phenomena, Philips said. The team is due to present its results in the July 8 issue of the journal Science.
Philips did not disclose the temperature of operation in the statement issued Monday (July 4).
The scientists have shown that the combination of indium arsenide semiconductor nanometer-scale wires with aluminum-based superconducting contacts results in reproducible superconducting transistors.
Despite a large number of semiconductor material systems and devices it has always proved difficult to combine semiconductors with superconducting materials, mainly because of the extremely low temperatures required for superconductivity.
In the Kavli-Philips devices a supercurrent can flow through the nanowire from one superconducting contact to the other. This quantum effect can be described as the "leakage" of Cooper pairs (paired electrons responsible for superconductivity) from the superconducting contacts into the semiconductor nanowire. Moreover, this supercurrent can be controlled by a gate voltage making it a supercurrent transistor.
Philips and Kavli used a recently developed method to grow the indium arsenide nanowires. The nanowires grow from small gold particles by a vapor-liquid-solid process. The size of the nanoparticles ranges from 10 nanometers to 100 nanometers, which sets the diameter of the nanowires, Philips said. The length of the nanowires is proportional to the growth time and can easily reach tens of microns providing a convenient aspect ratio for post-growth device fabrication, Philips added.
The yield of the superconducting devices is sufficiently high to allow superconducting circuits to include multiple Kavli-Philips nanowire devices.
Philips suggested that two nanowire devices could be used to build an electrically tunable superconducting quantum interference device (SQUID). A second possibility would be the creation of a nanowire light-emitting diode, which could be made by alternating the semiconductor vapor between n- and p-doped material during growth, which could be used to transfer quantum information from electrons to photons.
- Peter Clarke
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