Single-electron transistor: Difference between revisions

Revision as of 06:58, 20 September 2019

Revision as of 11:48, 4 November 2019

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[[File:Single electron transistor.svg|thumb|right|Left to right: energy levels of source, island and drain in a single-electron transistor for the blocking state (upper part) and transmitting state (lower part).]]

The SET has, Like the [[field-effect transistor|FET]], three electrodes: source, drain, and a gate. The main technological difference between the transistor types is in the channel concept. While the channel changes from insulated to conductive with applied gate voltage in the FET, the SET is always insulated. The source and drain are coupled through two [[Quantum tunnelling|tunnel junctions]], separated by a metallic or semiconductor-based [[quantum dot|quantum nanodot]] (QD)<ref name="UchidaMatsuzawa2000">{{cite journal|last1=Uchida|first1=Ken|last2=Matsuzawa|first2=Kazuya|last3=Koga|first3=Junji|last4=Ohba|first4=Ryuji|last5=Takagi|first5=Shin-ichi|last6=Toriumi|first6=Akira|title=Analytical Single-Electron Transistor (SET) Model for Design and Analysis of Realistic SET Circuits|journal=Japanese Journal of Applied Physics|volume=39|issue=Part 1, No. 4B|year=2000|pages=2321–2324|issn=0021-4922|doi=10.1143/JJAP.39.2321|bibcode=2000JaJAP..39.2321U}}</ref>, also known as the "island". The electrical potential of the QD can be tuned with the capacitively coupled gate electrode to alter the resistance, by applying a positive voltage the QD will change from blocking to non-blocking state and electrons will start tunnelling to the QD. This phenomenon is knwonknown as the [[Coulomb blockade]].

The current, <math>I,</math> from source to drain follows [[Ohm's_law|Ohm's law]] when <math>V_{\rm SD}</math> is applied, and it equals <math>\tfrac{V_{\rm SD}}{R},</math> where the main contribution of the resistance, <math>R,</math> comes from the tunnelling effects when electrons move from source to QD, and from QD to drain. <math>V_{\rm G}</math> regulates the resistance of the QD, which regulates the current. This is the exact same behaviour as in regular FETs. However, when moving away from the macroscopic scale, the quantum effects will affect the current, <math>I.</math>