Fine structure and magneto-optics of exciton, trion, and charged biexciton states in single InAs quantum dots emitting at1.3μm

Abstract

We present a detailed investigation into the optical characteristics of individual InAs quantum dots (QDs) grown by metalorganic chemical vapor deposition, with low temperature emission in the telecoms window around 1300 nm. Using micro-photoluminescence (PL) spectroscopy we have identified neutral, positively charged, and negatively charged exciton and biexciton states. Temperaturedependent measurements reveal dot-charging effects due to differences in carrier diffusivity. We observe a pronounced linearly polarized splitting of the neutral exciton and biexciton lines (∼250 µeV) resulting from asymmetry in the QD structure. This asymmetry also causes a mixing of the excited trion states which is manifested in the fine structure and polarization of the charged biexciton emission; from this data we obtain values for the ratio between the anisotropic and isotropic electron-hole exchange energies of∆1/∆0 ≈ 0.2-0.5. Magneto-PL spectroscopy has been used to investigate the diamagnetic response and Zeeman splitting of the various exciton complexes. We find a significant variation in g-factor between the exciton, the positive biexciton, and the negative biexciton; this is also attributed to anisotropy effects and the difference in lateral extent of the electron and hole wavefunctions.

Single quantum dot emission at telecom wavelengths from metamorphic InAs/InGaAs nanostructures grown on GaAs substrates

“…In InAs/GaAs QDs emitting in the same spectral region positive and negative trions are usually blue and redshifted with respect to X 0 by 1-2 meV and 5-7 meV, respectively. 23,27 Thus, results obtained here are in agreement with the ones measured in previous works. Finally, weak lines observed at 1.0560 and 1.0540 eV for medium-high excitation powers can have their origin on charged biexcitons and hence are labeled as XX ‫ء‬ but there is not enough information for a clearer identification.…”

Resolving Zeeman splitting in quantum dot ensembles

“…This allows an ensemble average g-factor g à ex;z ¼ À1:9260:04 to be determined for the undoped sample and g à ex;z ¼ À1:9160:02 for the sample doped at a level of 3 holes/QD. These values compare favorably with experiments performed on single QDs emitting at similar energies 3,11,12 and provide confidence in the applicability of the technique.…”

Photoluminescence spectroscopy of trions in quantum dots: A theoretical description

“…As a result, hole wave functions in the in-plane direction may be more or less delocalized than electron ones ͑the tighter localization in the vertical direction is more robust because the strong confinement overrides all other effects͒. 14,45 In quantum wires this asymmetry has been shown to strongly influence the properties of trions. 46 In this section, we investigate its effect on our previous results.…”