Abstract
We report the electronic characterization of mesoscopic Hall bar devices fabricated from coupled InAs/GaSb quantum wells sandwiched between AlSb barriers, an emerging candidate for two-dimensional topological insulators. The electronic width of the etched structures was determined from the low field magneto-resistance peak, a characteristic signature of partially diffusive boundary scattering in the ballistic limit. In case of dry-etching the electronic width was found to decrease with electron density. In contrast, for wet etched devices it stayed constant with density. Moreover, the boundary scattering was found to be more specular for wet-etched devices, which may be relevant for studying topological edge states.
Highlights
InAs/GaSb composite quantum wells have gained a lot of interest due to the prediction of the quantum spin Hall (QSH) state in the inverted regime[1] of the bandstructure
We report the electronic characterization of mesoscopic Hall bar devices fabricated from coupled InAs/GaSb quantum wells sandwiched between AlSb barriers, an emerging candidate for two-dimensional topological insulators
Recently, InAs/GaSb composite quantum wells have gained a lot of interest due to the prediction of the quantum spin Hall (QSH) state in the inverted regime[1] of the bandstructure
Summary
InAs/GaSb composite quantum wells have gained a lot of interest due to the prediction of the quantum spin Hall (QSH) state in the inverted regime[1] of the bandstructure In this state, transport is expected to be governed by counter propagating (helical) edge channels of opposite spins together with an insulating bulk and the system is referred to as a two-dimensional topological insulator (2D TI). Due to limited material quality often bulk transport is relevant and masks edge channel transport.[5] edge scattering originating from rough edges as a result of fabrication processes, can be detrimental to the observation of helical edge states.[10,11,12] Apart from being an emerging candidate for 2D TI, this system offers the potential to observe several physical phenomena such as exciton condensation,[13] Majorana Fermions,[14] or edge mode superconductivity.[15] In comparison to the HgTe/CdTe system, InAs/GaSb coupled quantum wells offer electric field tunability of the topological phase.[16]. The edge roughness in wet-etched devices was found to be smaller compared to dry-etched devices, which could be relevant for observing edge transport in this material
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