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4 results on '"Gkotinakos, A."'

1. Substitutional synthesis of sub-nanometer InGaN/GaN quantum wells with high indium content

Author

I. G. Vasileiadis, L. Lymperakis, A. Adikimenakis, A. Gkotinakos, V. Devulapalli, C. H. Liebscher, M. Androulidaki, R. Hübner, Th. Karakostas, A. Georgakilas, Ph. Komninou, E. Dimakis, and G. P. Dimitrakopulos

Subjects
Medicine, Science
Abstract

Abstract InGaN/GaN quantum wells (QWs) with sub-nanometer thickness can be employed in short-period superlattices for bandgap engineering of efficient optoelectronic devices, as well as for exploiting topological insulator behavior in III-nitride semiconductors. However, it had been argued that the highest indium content in such ultra-thin QWs is kinetically limited to a maximum of 33%, narrowing down the potential range of applications. Here, it is demonstrated that quasi two-dimensional (quasi-2D) QWs with thickness of one atomic monolayer can be deposited with indium contents far exceeding this limit, under certain growth conditions. Multi-QW heterostructures were grown by plasma-assisted molecular beam epitaxy, and their composition and strain were determined with monolayer-scale spatial resolution using quantitative scanning transmission electron microscopy in combination with atomistic calculations. Key findings such as the self-limited QW thickness and the non-monotonic dependence of the QW composition on the growth temperature under metal-rich growth conditions suggest the existence of a substitutional synthesis mechanism, involving the exchange between indium and gallium atoms at surface sites. The highest indium content in this work approached 50%, in agreement with photoluminescence measurements, surpassing by far the previously regarded compositional limit. The proposed synthesis mechanism can guide growth efforts towards binary InN/GaN quasi-2D QWs.

Published
2021
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3. Substitutional synthesis of sub-nanometer InGaN/GaN quantum wells with high indium content

Author

A. Adikimenakis, Liverios Lymperakis, M. Androulidaki, Emmanouil Dimakis, A. Gkotinakos, Alexandros Georgakilas, G. P. Dimitrakopulos, Philomela Komninou, Christian Liebscher, I. G. Vasileiadis, Theodoros Karakostas, Vivek Devulapalli, and René Hübner

Subjects
Multidisciplinary, Materials science, Photoluminescence, business.industry, Band gap, Superlattice, Science, Physics, chemistry.chemical_element, Heterojunction, Article, Engineering, chemistry, Nanoscience and technology, Optoelectronics, Medicine, Gallium, business, Indium, Quantum well, Molecular beam epitaxy
Abstract

InGaN/GaN quantum wells (QWs) with sub-nanometer thickness can be employed in short-period superlattices for bandgap engineering of efficient optoelectronic devices, as well as for exploiting topological insulator behavior in III-nitride semiconductors. However, it had been argued that the highest indium content in such ultra-thin QWs is kinetically limited to a maximum of 33%, narrowing down the potential range of applications. Here, it is demonstrated that quasi two-dimensional (quasi-2D) QWs with thickness of one atomic monolayer can be deposited with indium contents far exceeding this limit, under certain growth conditions. Multi-QW heterostructures were grown by plasma-assisted molecular beam epitaxy, and their composition and strain were determined with monolayer-scale spatial resolution using quantitative scanning transmission electron microscopy in combination with atomistic calculations. Key findings such as the self-limited QW thickness and the non-monotonic dependence of the QW composition on the growth temperature under metal-rich growth conditions suggest the existence of a substitutional synthesis mechanism, involving the exchange between indium and gallium atoms at surface sites. The highest indium content in this work approached 50%, in agreement with photoluminescence measurements, surpassing by far the previously regarded compositional limit. The proposed synthesis mechanism can guide growth efforts towards binary InN/GaN quasi-2D QWs.

Published
2021

4. At the Limit of Interfacial Sharpness in Nanowire Axial Heterostructures

Author

Hilliard, Donovan, Tauchnitz, Tina, Hübner, René, Vasileiadis, Isaak, Gkotinakos, Athanasios, Dimitrakopulos, George, Komninou, Philomela, Sun, Xiaoxiao, Winnerl, Stephan, Schneider, Harald, Helm, Manfred, and Dimakis, Emmanouil

Abstract

As semiconductor devices approach dimensions at the atomic scale, controlling the compositional grading across heterointerfaces becomes paramount. Particularly in nanowire axial heterostructures, which are promising for a broad spectrum of nanotechnology applications, the achievement of sharp heterointerfaces has been challenging owing to peculiarities of the commonly used vapor–liquid–solid growth mode. Here, the grading of Al across GaAs/AlxGa1–xAs/GaAs heterostructures in self-catalyzed nanowires is studied, aiming at finding the limits of the interfacial sharpness for this technologically versatile material system. A pulsed growth mode ensures precise control of the growth mechanisms even at low temperatures, while a semiempirical thermodynamic model is derived to fit the experimental Al-content profiles and quantitatively describe the dependences of the interfacial sharpness on the growth temperature, the nanowire radius, and the Al content. Finally, symmetrical Al profiles with interfacial widths of 2–3 atomic planes, at the limit of the measurement accuracy, are obtained, outperforming even equivalent thin-film heterostructures. The proposed method enables the development of advanced heterostructure schemes for a more effective utilization of the nanowire platform; moreover, it is considered expandable to other material systems and nanostructure types.

Published
2024
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