Independent control of exciton and biexciton energies in single quantum dots via electroelastic fields

Abstract

We investigate the effect of large in-plane strain and vertical electric fields on the binding energies of excitonic complexes confined in single InGaAs/GaAs quantum dots (QDs) and we find that the two independently tunable perturbations modify the interaction energies among electrons and holes in a different manner. By taking advantage of this difference, we frequency-lock the QD fundamental excitation (the neutral exciton) at a predefined value, while the biexciton transition is actively tuned from a binding to an antibinding configuration. Our electrically controlled dual-knob device demonstrates unprecedented control over the electronic properties of the few-particle states in a QD and may be applied to create novel energy-tunable sources of entangled photons using the time-reordering or the time-bin scheme.

Strain-inducedg-factor tuning in single InGaAs/GaAs quantum dots

“…The observed changes in the exciton g factor are significant, however relatively small (in the range of several percent). As the strain-induced shift in the emission energy is at least a factor of 15 smaller than what has been reported in literature for similar devices [12,17], we expect that the observed effect can be greatly enhanced. Using novel devices an even larger tuning range will be possible [28][29][30].…”

“…Using a flip-chip transfer onto a gold-coated piezoelectric actuator we are able to transfer the membranes to the piezo by gold thermocompression bonding, where the two surfaces are merged by applying simultaneously both force and heat. Using a similar device, Trotta et al [12] were able to vary the in-plane strain by as much as ∼ −0.4%, yielding shifts in the QD emission energy of around 15 meV.…”

“…The effects of strain on the electronic structure of semiconductor nanostructures have been extensively studied in the past, both theoretically and experimentally [12][13][14][15][16]. Therefore it is well known that strain profoundly modifies the band structure in a bulk semiconductor material.…”

“…For this particular dot the 2X 0 emission is at an higher energy than the X 0 emission, indicating a negative relative biexciton binding energy. For these dots this binding energy can be both positive and negative [12], causing the 2X 0 emission to be higher in energy than the X 0 emission in some dots and lower in others. Both X 0 and 2X 0 lines are indicated in Fig.…”

Semiconductor quantum dots as an ideal source of polarization-entangled photon pairs on-demand: a review

“…However, these structures are less suitable for entangled photon pair generation, as the energy difference between biexciton and exciton (relative binding energy) typically exceeds the width of the cavity resonance. We note here that the relative binding energy of the biexciton strongly depends on the QD structure [117] and that QDs with small binding energy can be found by careful preselection [118] or post-growth tuning via electric or strain fields [117,119]. Unless one resorts to the concept of time-reordering [120] -which is limited to nonunity values of the entanglement fidelity [121] -achieving at the same time vanishing FSS, binding energy and mode matching is however challenging.…”