Large-Scale Epitaxial Integration of Single-Crystalline BiSb Topological Insulator on GaAs (111)A

Topological insulators (TIs) are promising materials for future spintronics applications, and their epitaxial integration would allow the realization of hybrid interfaces. As the first materials studied, bismuth antimony alloys (Bi 1– x Sb x ) show great potential due to their tunable electronic band structure and efficient charge-to-spin conversion. Here, we report the growth of Bi 1– x Sb x thin films on GaAs (111)A substrates following two different protocols. For the conventional epitaxy process, the grown films show excellent crystallinity and twin domains corresponding to an in-plane 180° rotation of the crystalline structure. Domain walls are found to be composition-dependent and have a lower density for antimony-rich films. For the optimized process, depositing an antimony bilayer prior to BiSb growth allows for the achievement of single crystallinity of the TI films. The topologically protected surface states are evidenced by ex situ ARPES measurements for domain-free and conventional films. To the best of our knowledge, this work presents the first large-scale epitaxial integration of single-crystalline Bi 1– x Sb x thin films on industrial substrates.