Fine structure of bright and dark excitons in asymmetric droplet epitaxy GaAs/AlGaAs quantum dots

H. Mekni (1) , A. Pankratov (2) , S. Ben Radhia (1) , K. Boujdaria (1) , M. Chamarro (2) , C. Testelin (2)

1 University of Tunis El Manar
2 INSP-E12 - Photonique et cohérence de spin

We have calculated the exciton fine structure splittings (FSS) of asymmetric GaAs/AlGaAs quantum dots (QDs) obtained after Al droplet epitaxy and subsequent nanoholes formation followed by annealing and GaAs filling of nanoholes. We used a k • p model and considered the heavy-hole and light-hole mixing to calculate the electron-hole exchange interaction (EI). The two components, long-range (LR) and short-range (SR) of the EI, were deduced. The exciton fine structure is organized, as usual in zinc-blende compounds, into two groups of states: bright (optically active) and dark states. The bright-dark and bright-bright splittings contain LR and SR contributions, the LR part representing 5 to 68% of the total bright-dark splitting and 69 to 76% of the total bright-bright splitting for sizes experimentally explored. In QDs having C 2v symmetry, LR and SR contributions to dark-dark splitting have to be calculated at the second order of perturbation theory. A good agreement between the theory and experiment is obtained for QDs with different degrees of asymmetry, from QD having an isotropic shape to QD with a very anisotropic shape.

Domaines: Physique Quantique [quant-ph]; Science des matériaux [cond-mat.mtrl-sci]

H. Mekni, A. Pankratov, S. Ben Radhia, K. Boujdaria, M. Chamarro, et al.. Fine structure of bright and dark excitons in asymmetric droplet epitaxy GaAs/AlGaAs quantum dots. Physical Review B, 2021, 103 (7), ⟨10.1103/PhysRevB.103.075302⟩. ⟨hal-03156614⟩