Excitonic complexes in strain-free and highly symmetric GaAs quantum dots fabricated by filling of self-assembled nanoholes

Abstract

We perform a theoretical study of the optical transitions for different excitonic complexes in highly symmetric strain-free GaAs quantum dots (QDs) fabricated by epitaxially filling nanoholes (NHs) in an AlGaAs surface. NHs are formed by local droplet etching. As a first step, we propose a QD shape modeling consistent with atomic force microscopy (AFM) profiles and an experimental growth procedure. We investigate the QD height dependence of s- and p- shell exciton recombination energies in the framework of the effective mass approximation with an exact numerical diagonalization method. A comparison between theoretical results and available spectroscopic data is carried out. Systematic evolution of the binding energies of neutral (X), charged excitons (X–, X+) and the biexciton (XX), with QD height, is interpreted in terms of a balance between the Coulomb interactions and charge carrier correlation effects. Our calculations demonstrate the important role of the correlation energies in elucidating the bound character of all few-particle states especially the biexciton.

Comparative Chemico-Physical Analyses of Strain-Free GaAs/Al0.3Ga0.7As Quantum Dots Grown by Droplet Epitaxy

“…However, precise QD engineering (e.g., 3D geometric and compositional profiles) is required to sustain such a high capability of quantum networking. Several investigations have reported the fabrication of strain-free QDs using droplet epitaxy (DE) [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ] and by nanohole etching and infilling [ 15 , 16 , 17 , 18 , 19 ]. In the DE mode, QDs such as GaAs are crystallized by diffusing the initial liquid Ga droplets under an As flux, which avoids strain accumulation.…”

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

“…The shape of the GaAs QDs obtained by droplet epitaxy is modelled as in Refs. [36,37]. Two revolution ellipsoids with different centers and eccentricities allow us to define the shape contours of the GaAs QD.…”

“…These exchange couplings are particularly sensitive to QD anisotropy [40] or strain [41]. Following recent modelizations [36,37] (those works focusing on theoretical study of the electronic states, such as the single particles levels or single particle wave functions), we have derived the BD, DD, and BB splittings and compare our theoretical results with very recent microphotoluminescence measurements [21,22,37]. The calculated BB splitting is smaller than the experimental one while a good agreement between theory and existing experimental observation is obtained for BD and DD splittings.…”

“…More recently, by combining the k • p method for the computation of single-particle states and the CI method for excitonic states, it was possible to investigate the magneto-optical properties excitonic fine structure of GaAs/AlGaAs QDs obtained by droplet-etching method [34,35]. In the following, we will use a k • p approach, already used for similar GaAs/AlGaAs QDs [36,37]. We focus our study on the influence of the QD size and shape on the bright-dark (BD), dark-dark (DD), and brightbright (BB) exciton splittings.…”

Field‐Controlled Quantum Dot to Ring Transformation in Wave‐Function Tunable Cone‐Shell Quantum Structures

“…In order to keep the model simple, correlation effects are not considered here. Earlier models predict a small correlation energy of about 1 meV for neutral excitions in droplet etched GaAs quantum dots.…”