Strong Electric Polarizability of Cone–Shell Quantum Structures for a Large Stark Shift, Tunable Long Exciton Lifetimes, and a Dot-to-Ring Transformation

Heyn, Christian; Ranasinghe, Leonardo; Deneke, Kristian; Alshaikh, Ahmed; Duque, Carlos A.; Hansen, Wolfgang

doi:10.3390/nano13050857

Open AccessArticle

Strong Electric Polarizability of Cone–Shell Quantum Structures for a Large Stark Shift, Tunable Long Exciton Lifetimes, and a Dot-to-Ring Transformation

by

Christian Heyn

^1,*

,

Leonardo Ranasinghe

¹,

Kristian Deneke

¹,

Ahmed Alshaikh

¹,

Carlos A. Duque

²

and

Wolfgang Hansen

¹

Center for Hybrid Nanostructures (CHyN), University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany

²

Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín AA 1226, Colombia

^*

Author to whom correspondence should be addressed.

Nanomaterials 2023, 13(5), 857; https://doi.org/10.3390/nano13050857

Submission received: 30 January 2023 / Revised: 21 February 2023 / Accepted: 23 February 2023 / Published: 25 February 2023

(This article belongs to the Special Issue Quantum Nanostructures by Droplet Epitaxy for Optoelectronics and Quantum Information Technologies II)

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Abstract

Strain-free GaAs cone–shell quantum structures (CSQS) with widely tunable wave functions (WF) are fabricated using local droplet etching (LDE) during molecular beam epitaxy (MBE). During MBE, Al droplets are deposited on an AlGaAs surface, which then drill low-density (about 1 × 10

^{7}

cm⁻²) nanoholes with adjustable shape and size. Subsequently, the holes are filled with GaAs to form CSQS, where the size can be adjusted by the amount of GaAs deposited for hole filling. An electric field is applied in growth direction to tune the WF in a CSQS. The resulting highly asymmetric exciton Stark shift is measured using micro-photoluminescence. Here, the unique shape of the CSQS allows a large charge–carrier separation and, thus, a strong Stark shift of up to more than 16 meV at a moderate field of 65 kV/cm. This corresponds to a very large polarizability of 8.6 × 10

^{- 6}

eVkV

^{- 2}

cm². In combination with simulations of the exciton energy, the Stark shift data allow the determination of the CSQS size and shape. Simulations of the exciton–recombination lifetime predict an elongation up to factor of 69 for the present CSQSs, tunable by the electric field. In addition, the simulations indicate the field-induced transformation of the hole WF from a disk into a quantum ring with a tunable radius from about 10 nm up to 22.5 nm.

Keywords: droplet etching; quantum dot; quantum ring; photoluminescence; Stark shift; exciton lifetime; effective mass approximation

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MDPI and ACS Style

Heyn, C.; Ranasinghe, L.; Deneke, K.; Alshaikh, A.; Duque, C.A.; Hansen, W. Strong Electric Polarizability of Cone–Shell Quantum Structures for a Large Stark Shift, Tunable Long Exciton Lifetimes, and a Dot-to-Ring Transformation. Nanomaterials 2023, 13, 857. https://doi.org/10.3390/nano13050857

AMA Style

Heyn C, Ranasinghe L, Deneke K, Alshaikh A, Duque CA, Hansen W. Strong Electric Polarizability of Cone–Shell Quantum Structures for a Large Stark Shift, Tunable Long Exciton Lifetimes, and a Dot-to-Ring Transformation. Nanomaterials. 2023; 13(5):857. https://doi.org/10.3390/nano13050857

Chicago/Turabian Style

Heyn, Christian, Leonardo Ranasinghe, Kristian Deneke, Ahmed Alshaikh, Carlos A. Duque, and Wolfgang Hansen. 2023. "Strong Electric Polarizability of Cone–Shell Quantum Structures for a Large Stark Shift, Tunable Long Exciton Lifetimes, and a Dot-to-Ring Transformation" Nanomaterials 13, no. 5: 857. https://doi.org/10.3390/nano13050857

APA Style

Heyn, C., Ranasinghe, L., Deneke, K., Alshaikh, A., Duque, C. A., & Hansen, W. (2023). Strong Electric Polarizability of Cone–Shell Quantum Structures for a Large Stark Shift, Tunable Long Exciton Lifetimes, and a Dot-to-Ring Transformation. Nanomaterials, 13(5), 857. https://doi.org/10.3390/nano13050857

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Strong Electric Polarizability of Cone–Shell Quantum Structures for a Large Stark Shift, Tunable Long Exciton Lifetimes, and a Dot-to-Ring Transformation

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