First Principles Assessment of ZnTe and CdSe as Tunnel Barriers for the InAs/Al Interface*

Majorana zero modes, with prospective applications in topological quantum computing, are expected to arise at interfaces between a superconductor and a semiconductor with strong spin-orbit coupling, such as Al on InAs. 

However, proximity to the superconductor may also adversely affect the semiconductor’s local properties. A tunnel barrier inserted at the interface could resolve this issue by tuning the coupling strength. We assess the wide band gap semiconductors, ZnTe and CdSe, as candidate materials to mediate the coupling between Al and InAs. 

To this end, we use density functional theory (DFT) with Hubbard U corrections, whose values are machine-learned via Bayesian optimization. We study the band offsets and the penetration depth of metal-induced gap states (MIGS) in bilayer and tri-layer interfaces. DFT simulations indicate the relevant barrier thickness range to investigate experimentally.