Influence of lateral electric fields on multiexcitonic transitions and fine structure of single quantum dots

Abstract

The quantum-confined Stark effect of excitonic states in self-assembled (In,Ga)As∕GaAs quantum dots was studied by microphotoluminescence spectroscopy. A similar Stark-shift behavior for excitons, biexcitons, and a charged state was observed. Investigations suggest the absence of a permanent dipole moment in the lateral quantum dot plane. Values of the polarizability could be derived for all the investigated states. Furthermore, high-resolution Fabry-Pérot interferometry was applied to resolve the excitonic fine structure splitting and to investigate the influence of a lateral electric field. For a single dot, the splitting could be tuned to zero, thus affording the possibility to create electrically controlled entangled photon pairs.

Cascaded exciton emission of an individual strain-induced quantum dot

“…TR-PL revealed a delayed onset of lower occupancy states' signal in good agreement with a coupled rate equation model thus providing evidence without direct measurement of the crosscorrelation function. 12 These findings show that SI-QDs might provide a platform for a QD-based source of pairs of polarization entangled photons which does not require elaborate postselection 5 or finestructure tuning [13][14][15] schemes.…”

Statistical properties of exciton fine structure splitting and polarization angles in quantum dot ensembles

“…Now it is quite clear that the FSS arises from the intrinsic nonequivalence along [110] and [110] directions in zinc-blende crystals, which reduce the symmetry of the underlying lattice from T d to C 2v for pure circular lens-shaped QDs, and the other nonuniform effects such as local strain, shape irregularities, alloys and interface effects [10,11], which further reduce the symmetry to C 1 for alloyed QDs [12]. A single external field, such as electric field [13][14][15][16][17][18], magnetic field [2,19], or anisotropic stress [12,[20][21][22][23][24], is insufficient to eliminate the FSS because the lower bound of FSS is generally much larger than the homogeneous broadening of the emission line (∼ 1 µeV). To eliminate the FSS, two non-equivalent fields have to be combined [8,9].…”

Electric control of the exciton fine structure in nonparabolic quantum dots

“…Using a more realistic potential step (hard wall) barrier, we find a more complex relation between FSS and field and predict the possibility of a complete suppression of the FSS, as observed experiments [13]. We trace the additional FSS structure back to the fact that electron and hole wave functions are not only displaced but also deformed by the hard-wall potential.…”

“…Here we use a more realistic confinement potential and compare the obtained FSS to the one from harmonic confinement and to experimental results. Our theory explains the observed FSS in InGaAs QDs including the sign change of the FSS when a lateral electric field was applied [13]. In addition to the application of lateral electric fields, there are other methods of reducing the FSS by strain [5], vertical electric fields [17][18][19] or a magnetic field [20], as well as proposals to recover the entanglement in the presence of a finite FSS, such as spectral filtering [14,15], time reordering [16] or embedding the QD in an optical cavity [21].…”

“…We especially investigate the possibility of restoring degeneracy by virtue of applying an in-plane electric field. The dependence of the FSS on an in-plane electric field has been experimentally studied and it was confirmed that the FSS can be removed [12,13] but a complete theoretical understanding is still missing. Earlier work using a harmonic dot confinement potential find qualitatively different results [10].…”