Abstract
The fundamental understanding of quantum dot (QD) growth mechanism is essential to improve QD based optoelectronic devices. The size, shape, composition, and density of the QDs strongly influence the optoelectronic properties of the QDs. In this article, we present a detailed review on atomic-scale characterization of droplet epitaxy quantum dots by cross-sectional scanning tunneling microscopy (X-STM) and atom probe tomography (APT). We will discuss both strain-free GaAs/AlGaAs QDs and strained InAs/InP QDs grown by droplet epitaxy. The effects of various growth conditions on morphology and composition are presented. The efficiency of methods such as flushing technique is shown by comparing with conventional droplet epitaxy QDs to further gain control over QD height. A detailed characterization of etch pits in both QD systems is provided by X-STM and APT. This review presents an overview of detailed structural and compositional analysis that have assisted in improving the fabrication of QD based optoelectronic devices grown by droplet epitaxy.
Highlights
Semiconductor quantum dots (QDs) have been extensively studied in the last few decades due to their unique optoelectronic properties
In this review we present the results of detailed structural and composition analysis by cross-sectional scanning tunneling microscopy (X-Scanning tunneling microscope (STM)) and atom probe tomography (APT) of self-assembled QDs grown by licenses/by/4.0/)
Additional features are available in Transmission Electron Microscopy (TEM): an electron beam is swept in a raster over the sample producing a scanning transmission electron microscopy (STEM) image; Energy dispersive X-ray spectroscopy (EDX) can be used to estimate the composition of the sample [51]
Summary
Semiconductor quantum dots (QDs) have been extensively studied in the last few decades due to their unique optoelectronic properties. The optoelectronic properties of QDs are strongly influenced by the size, shape, and composition of the QDs. Precise tuning of the geometry and composition of QDs allows the optimization of both optical and electronic properties [1]. III-V semiconductor QDs offer such precise control where it has been shown that droplet epitaxy (DE) allows for a larger freedom in tuning the structural properties of quantum dot properties than is possible for quantum dots that are formed via the more common strain induced Stranski-Krastanov (SK) growth mode. A precise control and tuning of the QDs for various applications is only possible through a detailed understanding of the growth mechanism at the atomic level, which creates the need for atomic-scale structural and compositional characterization. Nanomaterials 2021, 11, 85 droplet epitaxy where we focus mainly on X-STM and APT characterization of strain-free. GaAs/AlGaAs and strained InAs/InP QDs grown by droplet epitaxy
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