Indium-antimonide ($\mathrm{In}\mathrm{Sb}$) two-dimensional electron gases (2DEGs) have a unique combination of material properties: high electron mobility, a strong spin-orbit interaction, a large Landé $g$ factor, and a small effective mass. This makes them an attractive platform to explore a variety of mesoscopic phenomena ranging from spintronics to topological superconductivity. However, there exist limited studies of quantum confined systems in these 2DEGs, often attributed to charge instabilities and gate drifts. We overcome this by removing the $\delta$-doping layer from the heterostructure and induce carriers electrostatically. This allows us to perform a detailed study of stable gate-defined quantum dots in $\mathrm{In}\mathrm{Sb}$ 2DEGs. We demonstrate two distinct strategies for carrier confinement and study the charge stability of the dots. The small effective mass results in a relatively large single-particle spacing, allowing for the observation of an even-odd variation in the addition energy. By tracking the Coulomb oscillations in a parallel magnetic field, we determine the ground-state spin configuration and show that the large $g$ factor (approximately 30) results in a singlet-triplet transition at magnetic fields as low as 0.3 T.

• Received 20 January 2020
• Revised 6 March 2020
• Accepted 17 March 2020

DOI:https://doi.org/10.1103/PhysRevApplied.13.041003