Growth and optimization of hybridized InAsSb/InGaSb topological superlattice materials

We are in the midst of the second quantum revolution. Research institutes and companies worldwide are working toward harnessing the power of quantum physics for technological applications. Gapless surface states on topological insulators are protected from elastic scattering on nonmagnetic impurities, which makes them promising candidates for low-power electronic applications. Conventional III–V infrared (IR) materials have the flexibility to engineer topologically protected surface states that can be resistant to ambient environments. In particular, largely hybridized band structures provide thermodynamically stable edge currents at the higher operating temperatures, which are important for IR sensing applications. Hence, we focused on optimizing two critical components for establishing ambient topological insulator; one for enlarging the hybridization gap, Δ, and the other for reducing bulk conduction in InAsSb/InGaSb structures. We performed a modelling study, and achieved an approximately 79 meV from InAs/InGaSb superlattices (SLs) lattice matched to AlSb, which is one of the largest reported value by far. Based on this modeling study, we selected a baseline SL design of InAsSb/GaSb on GaSb with Δ of ~62 meV to address key material issues such as finite bulk carrier conduction in undoped region of SLs. Systematic growth/processing optimization was performed in order to reduce the bulk charge carriers. The origin of constrained carrier dynamics in largely hybridized SL system and their effects on the designed topological structure were discussed.