The two-dimensional topological insulator state in InAs/GaSb quantum wells manifests itself by topologically protected helical edge channel transport relying on an insulating bulk. This work investigates a way of suppressing bulk conductivity by using gallium source materials of different degrees of impurity concentrations. While highest-purity gallium is accompanied by clear conduction through the sample bulk, intentional impurity incorporation lead to a bulk resistance over 1 M\Omega. This resistance was found to be independent of applied magnetic fields. Ultra high electron mobilities for GaAs/AlGaAs structures fabricated in a molecular beam epitaxy system used for the growth of Sb-based samples are reported.
@article{arxiv.1308.3375,
title = {Suppression of bulk conductivity in InAs/GaSb broken gap composite quantum wells},
author = {Christophe Charpentier and Stefan Fält and Christian Reichl and Fabrizio Nichele and Atindra Nath Pal and Patrick Pietsch and Thomas Ihn and Klaus Ensslin and Werner Wegscheider},
journal= {arXiv preprint arXiv:1308.3375},
year = {2014}
}