Semiconductor-rich group iv quantum alloys: the role of atomic ordering
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Authors
Liang, Yunfan
Issue Date
2025-05
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Physics
Alternative Title
Abstract
Recent years have witnessed rapid progress in topological quantum physics, as it introduces a new dimension in solid state physics with high potential for technological breakthroughs. Despite the explosion of interest in topological materials, their applications remain limited due to challenges in growth and incorporation with today’s microelectronics. As a potential bridge to close this gap, we propose two different strategies to achieve topological properties in Ge based alloys with ~90% Ge concentration and confirm that the atomic ordering in these alloy systems can serve as a new freedom to tune the topological properties. In the first case of GePb alloy, the random alloy with ~9% Pb can exhibit topological insulator phase, whereas atomic short-range order tends to disrupt this topology, resulting in a trivial insulator phase. This reveals that even with fixed Pb concentration, the topological properties can be tuned by manipulating the degree of SRO. However, Studies on GePb epitaxy remain limited, posing challenges for experimental realization. To propose a more experimentally accessible group-IV quantum alloy, we went in a completely different direction in the second case of GeSn alloys. Instead of using the randomness of the alloys, we proposed using ordered digital alloy structures where along one direction the Sn are ordered to form a superlattice in Ge. This made it possible for the Ge/Sn system to exhibit a rich variety of topological properties, such as triple-point semimetals, Weyl semimetals and weak topological insulators, at low Sn concentration of only 10%, which is much lower than the >35% required in GeSn random alloy. Additionally, we provide theoretical insight into the dynamic process of SRO formation during epitaxy, showing that the degree of SRO can be tuned by applying different growth techniques (MBE or CVD).
Description
May2025
School of Science
School of Science
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY