Growth of shallow GaAs quantum dots and investigation of their optical properties

Date

Dec 2, 2022

Time

10:00 AM - 11:00 AM

Speaker

Moritz Langer

Affiliation

IFW Dresden

Language

en

Main Topic

Materialien

Host

Ines Firlle

Description

In recent years local droplet etching developed into an attractive growth process for GaAs strain-free semiconductor quantum dots [1]. Typically, the conical etched nanoholes in Al0.15Ga0.85As matrix material have widths of about 50 nm and depths of 15 nm. Using migration enhanced epitaxy these nanoholes are filled with GaAs to a height of around 6 nm and are consequently capped by a layer of matrix material. Usually, capping layers of >100nm are used to retain electrical and optical properties of the quantum dots in the surrounding AlxGa1-xAs matrix material and reduce external influences such as surface defects. Through this quantum dots of high optical quality and brightness are obtained [2]. For enhanced interaction of quantum dots with external stimuli – e.g. magnetic fields of thin films and usage of quantum dots as localized quantum sensors as well as waveguide coupled single-photon emitters [5], it is desirable to reduce the spatial distance and obtain quantum dots close to the surface. Consequentially, the nature of the sample surface and the electronic and optical properties of these quantum dots cannot be considered independently. For this purpose, the influence of capping layer thickness on the optical properties of GaAs/Al0.15Ga0.85As quantum dots are investigated using photoluminescence spectroscopy. For many years quantum dots with a capping layer <12 nm were considered as a non-feasible challenge [3-5]. Our recent results contradict this opinion, they show optical active quantum dots below this limit and have the potential to pave the way for a completely new class of integrated quantum dots technology. This work will focus on a deeper physical understanding of the dominating effects on quantum dots close to the surface, their experimental realization and physical limitations. Suitable passivation of surface defects appears to be essential for the realization of bright quantum dots close to the surface [6]. For this purpose, in-situ passivation methods, such as high band-gap materials or solution-based surface passivation are investigated. [1] X. Huang et al., Nanotechnology 31 495701 (2020) [2] R. Keil, Dissertation “Growth, characterization and implementation of semiconductor sources of highly entangled photons”, 2019 [3] C. Heyn et al., J. Appl. Phys. 121, 044306 (2017) [4] S. Manna et al., Appl. Surf. Sci. 532, 147360 (2020) [5] X. Cao et al., Appl. Phys. Lett. 118, 221107 (2021) [6] X. Cao et al., arXiv:2207.13387 (2022)

Links

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Last modified: Nov 30, 2022, 7:38:53 AM