Electronic Structure of InAs and InSb Surfaces: Density Functional Theory and Angle‐Resolved Photoemission Spectroscopy

Abstract

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. Here, the electronic structure of InAs(001), InAs(111), and InSb(110) surfaces is studied using a combination of density functional theory (DFT) and angle‐resolved photoemission spectroscopy (ARPES). Large‐scale first principles simulations are enabled by using DFT calculations with a machine‐learned Hubbard U correction [npj Comput. Mater. 6, 180 (2020)]. To facilitate direct comparison with ARPES results, a “bulk unfolding” scheme is implemented by projecting the calculated band structure of a supercell surface slab model onto the bulk primitive cell. For all three surfaces, a good agreement is found between DFT calculations and ARPES. For InAs(001), the simulations clarify the effect of the surface reconstruction. Different reconstructions are found to produce distinctive surface states, which may be detected by ARPES with low photon energies. For InAs(111) and InSb(110), the 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. The combined theoretical and experimental results may inform the design of quantum devices based on InAs and InSb semiconductors, for example, topological qubits utilizing the Majorana zero modes.

First principles feasibility assessment of a topological insulator at the InAs/GaSb interface

“…For interface calculations a 8×8×1 k-point grid was used to sample the interface Brillouin zone and dipole corrections [64] were included. Bulk unfolding [65] was applied to project interface band structures onto the primitive cell, as described in the SI.…”

“…"A/B" is used to describe an InAs/GaSb interface with A layers of InAs and B layers of GaSb. A vacuum region of about 40 A was added to the interface model to prevent spurious interactions between periodic images (for the purpose of band unfolding the closest integer number of primitive cells to 40 A was used [65]). In order to terminate dangling bonds, In and Ga atoms on the surface were passivated by pseudo hydrogen atoms with 1.25 fractional electrons, whereas As and Sb atoms on the surface were passivated by pseudo hydrogen atoms with 0.75 fractional electrons.…”

“…The number of layers included in slab models needs to be converged to the bulk limit to avoid quantum size effects. For semiconductors the band gap is typically used as a the convergence criterion [65,76]. Fig.…”

First Principles Study of the Electronic Structure of the Ni$_2$MnIn/InAs and Ti$_2$MnIn/InSb interfaces

“…Point contact Andreev reflectometry (PCAR) further showed a spin polarization around 17% in a 155 nm Ni 2 MnIn layer, although with a relatively rough surface and possibly B2 ordering [67][68][69][70]. PCAR measurements on Ni 2 MnIn grown on InAs (110) showed spin polarization of 28% [71,72]. Ref.…”

“…Band matching considerations were then used to predict the spin transport at the interface with InAs, assuming Fermi level pinning slightly above the InAs conduction band minimum. A free-electron model, described below, gives transmittance (T) along three high symmetry directions as T [100] =0.75(0.19), T [110] =0.82(0.19), and T [111] =0.99(0.39) for the minority (majority) spin bands. Subsequently, Ref.…”