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

摘要

We present a detailed investigation into the optical characteristics ofindividual InAs quantum dots (QDs) grown by metalorganic chemical vapordeposition, with low temperature emission in the telecoms window around 1300nm. 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 todifferences in carrier diffusivity. We observe a pronounced linearly polarizedsplitting of the neutral exciton and biexciton lines (~250 ueV) resulting fromasymmetry in the QD structure. This asymmetry also causes a mixing of theexcited trion states which is manifested in the fine structure and polarizationof the charged biexciton emission; from this data we obtain values for theratio between the anisotropic and isotropic electron-hole exchange energies of(Delta1)/(Delta0)= 0.2--0.5. Magneto-PL spectroscopy has been used toinvestigate the diamagnetic response and Zeeman splitting of the variousexciton complexes. We find a significant variation in g-factor between theexciton, the positive biexciton, and the negative biexciton; this is alsoattributed to anisotropy effects and the difference in lateral extent of theelectron and hole wavefunctions.