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Effects of biased and unbiased illuminations on two-dimensional electron gases in dopant-free GaAs/AlGaAs

Shetty, A; Sfigakis, F; Mak, WY; Das Gupta, K; Buonacorsi, B; Tam, MC; Kim, HS; ... Baugh, J; + view all (2022) Effects of biased and unbiased illuminations on two-dimensional electron gases in dopant-free GaAs/AlGaAs. Physical Review B , 105 (7) , Article 075302. 10.1103/PhysRevB.105.075302. Green open access

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Abstract

Illumination is performed at low temperature on dopant-free two-dimensional electron gases (2DEGs) of varying depths, under unbiased (gates grounded) and biased (gates at a positive or negative voltage) conditions. Unbiased illuminations in 2DEGs located more than 70 nm away from the surface result in a gain in mobility at a given electron density, primarily driven by the reduction of background impurities. In 2DEGs closer to the surface, unbiased illuminations result in a mobility loss, driven by an increase in surface charge density. Biased illuminations performed with positive applied gate voltages result in a mobility gain, whereas those performed with negative applied voltages result in a mobility loss. The magnitude of the mobility gain (loss) weakens with 2DEG depth, and is likely driven by a reduction (increase) in surface charge density. Remarkably, this mobility gain/loss is fully reversible by performing another biased illumination with the appropriate gate voltage, provided both Formula Presented-type and Formula Presented-type Ohmic contacts are present. Experimental results are modeled with Boltzmann transport theory, and possible mechanisms are discussed.

Type: Article
Title: Effects of biased and unbiased illuminations on two-dimensional electron gases in dopant-free GaAs/AlGaAs
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevB.105.075302
Publisher version: https://doi.org/10.1103/PhysRevB.105.075302
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10144554
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