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.

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The discovery of topological insulators (TIs) and their unique electronic properties has motivated research into a variety of applications, including quantum computing. It has been proposed that TI surface states will be energetically discretized in a quantum dot nanoparticle. These discretized states could then be used as basis states for a qubit that is more resistant to decoherence. In this work, prototypical TI Bi2Se3 nanoparticles are grown on GaAs (001) using the droplet epitaxy technique, and we demonstrate the control of nanoparticle height, area, and density by changing the duration of bismuth deposition and substrate temperature. Within the growth window studied, nanoparticles ranged from 5 to 15 nm in height with an 8–18 nm equivalent circular radius, and the density could be relatively well controlled by changing the substrate temperature and bismuth deposition time.

As a highly mismatched alloy class, dilute bismuthide materials exhibit strong valence band-Bi impurity state interactions, leading to large bandgap bowing parameters and strong spin–orbit coupling due to the inclusion of Bi in III-V semiconductors. Such properties make the dilute bismuthides ideal candidates for devices requiring band and strain engineering, particularly those in the infrared regions. In this work, the molecular beam epitaxy growth of the dilute bismuthide InxAl1−xBiyAs1−y on InP is studied. To address challenges universally faced in dilute bismuthide growth, a growth–space diagram is constructed to better understand the conditions needed for Bi incorporation and droplet-free growth of the class of dilute bismuthide materials. From this understanding, high-quality, droplet-free growth of In0.52Al0.48BiyAs1−y with up to 5.1% Bi is demonstrated. The n-type unintentional doping of these films is found to be ∼1013–1015 cm−3 with a free carrier mobility of ∼700–1500 cm2/(V s). From these films, the compressive strain induced by Bi incorporation is measured to be (0.190 ± 0.004)% strain/(% Bi) for In0.52Al0.48BiyAs1−y. Using this value to offset strain, lattice-matched InxAl1−xBiyAs1−y on InP is demonstrated.