Materials considerations for forming the topological insulator phase in InAs/GaSb heterostructures

Abstract

In an ideal InAs/GaSb bilayer of appropriate dimension in-plane electron and hole bands overlap and hybridize, and a topologically non-trivial, or quantum spin Hall (QSH) insulator, phase is predicted to exist. The in-plane dispersion's potential landscape, however, is subject to microscopic perturbations originating from material imperfections. In this work, the effect of disorder on the electronic structure of InAs/GaSb bilayers was studied by the temperature and magnetic field dependence of the resistance of a dual-gated heterostructures gate-tuned through the inverted to normal gap regimes. Conduction in the inverted (predicted topological) regime was qualitatively similar to behavior in a disordered two-dimensional system. The impact of charged impurities and interface roughness on the formation of topologically protected edge states and an insulating bulk was estimated. The experimental evidence and estimates of disorder in the potential landscape indicated the potential fluctuations in state-of-the-art films are sufficiently strong such that conduction in the predicted topological insulator (TI) regime was dominated by a symplectic metal phase rather than a TI phase. The implications are that future efforts must address disorder in this system and focus must be placed on the reduction of defects and disorder in these heterostructures if a TI regime is to be achieved.

16 pages, including 6 figures

References in corpus (7)

• Quantum Spin Hall Effect in Inverted Type II Semiconductors
• Resistance of helical edges formed in a semiconductor heterostructure
• Electric and Magnetic Tuning Between the Trivial and Topological Phases in InAs/GaSb Double Quantum Wells
• Gate-controlled semimetal-topological insulator transition in an InAs/GaSb heterostructure
• Magnetotransport in disordered delta-doped heterostructures
• Transport in two-dimensional disordered semimetals
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Cited by in corpus (9)

• Helical Liquids in Semiconductors
• High mobility InAs 2DEGs on GaSb substrates: a platform for mesoscopic quantum transport
• Anomalous Quantum Oscillations of Interacting Electron-hole Gases in Inverted Type-II InAs/GaSb Quantum Wells
• Intrinsic point defects and the $n$- and $p$-type dopability of the narrow gap semiconductors GaSb and InSb
• First principles feasibility assessment of a topological insulator at the InAs/GaSb interface
• Energy gap tuning and gate-controlled topological phase transition in InAs/In${}_x$Ga${}_{1-x}$Sb composite quantum wells
• Interaction-induced crossover between weak anti-localization and weak localization in a disordered InAs/GaSb double quantum well
• Localization of trivial edge states in InAs/GaSb composite quantum wells
• Impact of epitaxial strain on the topological-nontopological phase diagram and semimetallic behavior of InAs/GaSb composite quantum wells