Characterization of epitaxial Bi1-xSbx topological insulator thin films on GaAs(111) substrates
Résumé
Topological Insulators (TI) are a new class of materials that are insulators in the bulk and conductors at the surface. They were theoretically predicted by Fu and Kane in 2007 [1] and reported experimentally in 2008 [2]. Among these TIs, bismuth-antimony alloys (Bi1−xSbx) are the first reported 3D TI for x compositions ranging from 7 to 22%. It remains the most promising for spintronic applications thanks to its large conductivity, colossal spin Hall angle, and the possibility of building low-current spin-orbit-torque magnetoresistive random access memories. We recently reported the growth of high-quality BiSb thin layers on GaAs(111)A substrates, thanks to optimized surface preparation and demonstrated its monocrystalline nature [3]. ARPES and electrical measurements demonstrate the topologically protected nature of the surface states. Here, we report the growth of Bi1−xSbx thin films on GaAs (111)A substrates with thicknesses ranging from 20nm to 100nm. The influence of thickness on both the bulk and the surface transport properties is revealed by temperature dependent Hall effect measurements carried out between 20 and 300K.