Electronic Structure of InAs and InSb Surfaces: Density Functional Theory (DFT) and Angle-Resolved Photoemission Spectroscopy (ARPES)*

The electronic structure of surfaces plays a key role in the properties of quantum devices. However, surfaces are also the most challenging to simulate and engineer. We study the electronic structure of InAs(001), InAs(111), and InSb(110) surfaces using a combination of DFT and ARPES. Large-scale DFT simulations are enabled by using a machine-learned Hubbard U correction [npj Comput. Mater. 6, 180 (2020)]. To facilitate direct comparison with ARPES, we implemented a "bulk unfolding" scheme for projecting the calculated band structure of a supercell surface slab model onto the bulk primitive cell. For all three surfaces, DFT is in good agreement with ARPES. For InAs(001), simulations clarify the effect of surface reconstruction. Different reconstructions produce distinctive surface states, which may be detected by ARPES with low photon energies. For InAs(111) and InSb(110),  simulations help elucidate the effect of oxidation. Owing to larger charge transfer from As to O than from Sb to O, oxidation of InAs(111) leads to significant band bending and produces an electron pocket, whereas oxidation of InSb(110) does not. Our combined theoretical and experimental results may inform the design of quantum devices involving InAs and InSb, e.g., Majorana-based qubits.