A Single-Electron Transistor (SET) is a switching device that uses controlled electron tunneling to manipulate the flow of single electrons. It consists of a quantum dot (the ‘island’) coupled to source and drain leads via tunnel junctions, and capacitively coupled to a gate electrode. Its operation relies on the Coulomb blockade effect, enabling extreme sensitivity and low power consumption.
Single-Electron Transistor (SET)
- Dmitri Averin
- Konstantin Likharev
The Single-Electron Transistor (SET) operates based on a quantum mechanical effect called the Coulomb blockade. This effect occurs in a very small conductive island (a quantum dot) connected to source and drain electrodes through two tunnel junctions. For an electron to tunnel onto the island, it must overcome the electrostatic repulsion from the electrons already present. This requires a charging energy, [latex]E_C = e^2 / (2C)[/latex], where [latex]e[/latex] is the elementary charge and [latex]C[/latex] is the total capacitance of the island. For the Coulomb blockade to be observable, this charging energy must be significantly larger than the thermal energy, [latex]k_B T[/latex], which necessitates cryogenic temperatures and/or extremely small island capacitance (fF or aF).
A gate electrode is capacitively coupled to the island. By applying a voltage [latex]V_g[/latex] to the gate, the electrostatic potential of the island can be precisely tuned. This gate voltage can be adjusted to overcome the Coulomb blockade, allowing a single electron to tunnel from the source onto the island, and then from the island to the drain. This process can be repeated one electron at a time. The current through the SET thus exhibits sharp peaks (Coulomb oscillations) as a function of the gate voltage, with each peak corresponding to the addition of one electron to the island. This makes the SET an extremely sensitive electrometer, capable of detecting fractions of an elementary charge.
While SETs offer unparalleled sensitivity and potential for ultra-low power logic, their practical application in large-scale circuits is hindered by several challenges. The requirement for very low temperatures is a major obstacle for consumer electronics. Furthermore, their performance is highly sensitive to random background charges in the surrounding substrate, which can unpredictably shift the gate voltage characteristics. Fabricating large arrays of identical SETs with high yield is also extremely difficult. Despite these hurdles, they remain a vital tool in fundamental physics research and are actively being explored for niche applications like quantum information processing, where the charge state of a quantum dot can represent a qubit.
Type
Disruption
Utilisation
Precursors
- discovery of the electron
- concept of quantum tunneling
- invention of the field-effect transistor (FET)
- development of quantum dots
- theory of coulomb blockade
Applications
- highly sensitive electrometers
- single-photon detectors
- research in quantum computing (qubits)
- low-temperature physics experiments
- metrology normes for electric current
Brevets :
Potential Innovations Ideas
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Historical Context
Single-Electron Transistor (SET)
(if date is unknown or not relevant, e.g. "fluid mechanics", a rounded estimation of its notable emergence is provided)
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