Semiconductor quantum dots with light-hole exciton ground state: fabrication and fine structure

TL;DR

This paper demonstrates the fabrication of GaAs/AlGaAs quantum dots with a light-hole exciton ground state using tensile strain, enabling new possibilities for quantum information applications.

Contribution

It introduces a method to switch the exciton ground state from heavy-hole to light-hole in quantum dots through tensile strain, supported by experimental and theoretical analysis.

Findings

Light-hole exciton ground state achieved in GaAs/AlGaAs QDs

Fine structure characterized by in-plane and out-of-plane polarized lines

Consistent with atomistic pseudopotential calculations

Abstract

Quantum dots (QDs) can act as convenient hosts of two-level quantum szstems, such as single electron spins, hole spins or excitons (bound electron-hole pairs). Due to quantum confinement, the ground state of a single hole confined in a QD usually has dominant heavy-hole (HH) character. For this reason light-hole (LH) states have been largely neglected, despite the fact that may enable the realilzation of coherent photon-to-spin converters or allow for faster spin manipulation compared to HH states. In this work, we use tensile strains larger than 0.3% to switch the ground state of excitons confined in high quality GaAs/AlGaAs QDs from the conventional HH- to LH-type. The LH-exciton fine structure is characterized by two in-plane-polarized lines and, ~400 micro-eV above them, by an additional line with pronounced out-of-plane oscillator strength, consistent with theoretical predictions based on atomistic empirical pseudopotential calculations and a simple mesoscopic model.