Fine structure and magneto-optics of exciton, trion, and charged biexciton states in single InAs quantum dots emitting at 1.3 um

TL;DR

This study provides a comprehensive analysis of the optical properties of individual InAs quantum dots emitting at 1.3 μm, focusing on exciton, trion, and biexciton states, revealing fine structure, polarization effects, and magnetic responses.

Contribution

It offers new insights into the fine structure, polarization, and magnetic properties of excitonic states in InAs quantum dots within the telecom wavelength range.

Findings

Identification of neutral, charged exciton and biexciton states.

Observation of polarization splitting (~250 μeV) due to structural asymmetry.

Variation in g-factors linked to anisotropy and wavefunction extent.

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. Temperature-dependent 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 ueV) 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 (Delta1)/(Delta0)= 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.