Tailoring growth mode during molecular beam epitaxial growth of InSbBi thin films on InSb(001) for enhanced Bi incorporation

With a bandgap of <0.17 eV, indium antimonide bismide (InSbBi) has emerged as a promising material for long-wavelength infrared photodetectors. It also processes strong spin-orbit coupling and a large Landé g-factor, making it ideal for semiconductor-superconductor hybrid systems that enable quantum phenomena such as topological superconductivity and the superconducting diode effect. However, achieving high-quality InSbBi remains challenging due to difficulties in Bi incorporation. In this study, we have developed a molecular beam epitaxial growth method to synthesize high-quality InSbBi thin films with tunable Bi incorporation up to 1.81 atom % by adjusting the Sb flux dynamically and controlling the growth temperature and Bi flux. A surface morphology transition from Stranski–Krastanov (SK) to step-flow growth was observed as the growth temperature increased from 200°C to 250°C, with SK growth dominant at lower temperatures where Bi incorporation was found to occur. Magneto-transport measurements on our best films revealed they were n-type with electron mobilities greater than 1900 cm²/V·s and weak localization up to 80 K. Our findings advance the development of InSbBi thin films for photodetection and quantum transport applications.