Clean quantum point contacts in an InAs quantum well grown on a lattice-mismatched InP substrate

TL;DR

This paper demonstrates the creation of high-quality quantum point contacts in InAs quantum wells on InP substrates, revealing quantized conductance and detailed spin properties despite lattice mismatch.

Contribution

It reports the first realization of clean, quantized QPCs in InAs on InP with detailed spin and subband analysis, overcoming lattice mismatch challenges.

Findings

Up to eight conductance plateaus observed at zero magnetic field

Harmonic confinement potential with 5 meV subband spacing

Enhanced out-of-plane g factor of approximately 27

Abstract

Strong spin-orbit coupling, the resulting large $g$ factor, and small effective mass make InAs an attractive material platform for inducing topological superconductivity. The surface Fermi level pinning in the conduction band enables highly transparent ohmic contact without excessive doping. We investigate electrostatically defined quantum point contacts (QPCs) in a deep-well InAs two-dimensional electron gas. Despite the 3.3% lattice mismatch between the InAs quantum well and the InP substrate, we report clean QPCs with up to eight pronounced quantized conductance plateaus at zero magnetic field. Source-drain dc bias spectroscopy reveals a harmonic confinement potential with a nearly $5$ meV subband spacing. We find a many-body exchange interaction enhancement for the out-of-plane $g$ factor $|g_{\perp}^*| = 27 \pm 1$, whereas the in-plane $g$ factor is isotropic $|g^*_{x}| = |g^*_{y}| = 12 \pm 2$, close to the bulk value for InAs.