We realize strongly confined quantum dots (QDs) in InAs nanowires (NWs) by combining epitaxial crystal-phase control with chemical wet etching. A strong axial confinement is first introduced by growing closely spaced wurtzite (WZ) tunnel barriers in NWs to enclose a zinc blende (ZB) QD. The NW cross-section is then reduced by isotropic etching to obtain very small QDs, with a maximum observed charging energy > 30 meV. Using low-temperature electrical characterization and finite-element method simulations, we study how charging energies and the onset of electron filling scale with QD diameter. For extremely small diameters, we identify a regime where stray capacitances become non-negligible, limiting further increase in charging energy by diameter reduction alone. This approach to increasing confinement is particularly relevant for understanding the strong spin-orbit interaction observed in crystal-phase QDs, possibly linked to polarization charges at the WZ/ZB interfaces. Small diameter QDs allow considerably weaker interfering electric fields when studied, but the QDs cannot be realized with epitaxial growth alone due to a loss of crystal phase control.
@article{arxiv.2511.23019,
title = {Radial etching of strongly confined crystal-phase defined quantum dots},
author = {Markus Aspegren and Chris Mkolongo and Sebastian Lehmann and Kimberly Dick and Adam Burke and Claes Thelander},
journal= {arXiv preprint arXiv:2511.23019},
year = {2025}
}
Comments
12 pages, 3 figures in main text, 3 supplementary figures