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

TL;DR

This paper demonstrates the first large-scale epitaxial growth of single-crystalline BiSb topological insulator films on GaAs (111)A substrates, highlighting optimized protocols for high-quality film production and surface state verification.

Contribution

It introduces a novel large-scale epitaxial process for BiSb films on GaAs substrates, achieving single crystallinity and verifying topological surface states.

Findings

Optimized process yields single-crystalline BiSb films.

Surface states confirmed by ARPES measurements.

Domain walls are composition-dependent and reduced in Antimony-rich films.

Abstract

Topological insulators (TI) are promising materials for future spintronics applications and their epitaxial integration would allow the realization of new hybrid interfaces. As the first materials studied, Bismuth Antimony alloys (Bi1-xSbx) show great potential due to their tuneable electronic band structure and efficient charge-to-spin conversion. Here, we report the growth of Bi1-xSbx 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{\textdegree} 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 achieving single crystallinity of the TI films. The topologically protected surface states are evidenced by ex-situ ARPES measurements for domains-free and conventional films. To the best of our knowledge, this work presents the first large-scale epitaxial integration of single crystalline Bi1-xSbx thin films on industrial substrates.