Journal
ACS APPLIED NANO MATERIALS
Volume 5, Issue 6, Pages 8070-8079Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsanm.2c01197
Keywords
InAs/InP quantum dots; droplet epitaxy; substrate etching; X-STM; InAs etch pits
Funding
- European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie project 4PHOTON [721394]
- Dutch Research Council (NWO) Zwaartekracht Project on Integrated Nanophotonics [10018478]
- EPSRC National Hub for High Value Photonics Manufacturing [EP/N00762X/1]
- EPSRC [EP/N00762X/1] Funding Source: UKRI
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We present a detailed atomic-resolution study of morphology and substrate etching mechanism in InAs/InP droplet epitaxy quantum dots (QDs) grown by metal-organic vapor phase epitaxy via cross-sectional scanning tunneling microscopy (X-STM). We observed two different etching processes, local drilling and long-range etching, depending on the crystallization temperature. The study also revealed the formation of trenches and provided insights into the composition and fine structure splitting of the QDs.
We present a detailed atomic-resolution study of morphology and substrate etching mechanism in InAs/InP droplet epitaxy quantum dots (QDs) grown by metal-organic vapor phase epitaxy via cross-sectional scanning tunneling microscopy (X-STM). Two different etching processes are observed depending on the crystallization temperature: local drilling and long-range etching. In local drilling occurring at temperatures of <= 500 degrees C, the In droplet locally liquefies the InP underneath and the P atoms can easily diffuse out of the droplet to the edges. During crystallization, the As atoms diffuse into the droplet and crystallize at the solid-liquid interface, forming an InAs etch pit underneath the QD. In long-range etching, occurring at higher temperatures of >500 degrees C, the InP layer is destabilized and the In atoms from the surroundings migrate toward the droplet. The P atoms can easily escape from the surface into the vacuum, forming trenches around the QD. We show for the first time the formation of trenches and long-range etching in InAs/InP QDs with atomic resolution. Both etching processes can be suppressed by growing a thin layer of InGaAs prior to the droplet deposition. The QD composition is estimated by finite element modeling in combination with X-STM. The change in the morphology of QDs due to etching can strongly influence the fine structure splitting. Therefore, the current atomic-resolution study sheds light on the morphology and etching behavior as a function of crystallization temperature and provides a valuable insight into the formation of InAs/InP droplet epitaxy QDs which have potential applications in quantum information technologies.
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