Bi₂Se₃ Growth on (001) GaAs Substrates for Terahertz Integrated Systems

Terahertz (THz) technologies have been of interest for many years due to the variety of applications including gas sensing, nonionizing imaging of biological systems, security and defense, and so forth. To date, scientists have used different classes of materials to perform different THz functions. However, to assemble an on-chip THz integrated system, we must understand how to integrate these different materials. Here, we explore the growth of Bi₂Se₃, a topological insulator material that could serve as a plasmonic waveguide in THz integrated devices, on technologically important GaAs(001) substrates. We explore surface treatments and find that an atomically smooth GaAs surface is critical to achieving high-quality Bi₂Se₃ films despite the relatively weak film/substrate interaction. Calculations indicate that the Bi₂Se₃/GaAs interface is likely selenium-terminated and shows no evidence of chemical bonding between the Bi₂Se₃ and the substrate. These results are a guide for integrating van der Waals materials with conventional semiconductor substrates and serve as the first steps toward achieving an on-chip THz integrated system.