Redshift of the excited state due to a nondegenerate biexciton in self-organized quantum dots

Abstract

Using femtosecond differential transmission spectroscopy, we observed a “nondegenerate” biexciton, consisting of an electron-hole pair in the dot ground state and an electron-hole pair in the excited state, in InGaAs self-organized quantum dots. We resonantly pumped the ground state transition in the quantum dots and observed an induced resonance in the probe differential transmission spectrum near the first excited-state transition, which we attribute to the formation of a nondegenerate biexciton state. The binding energy of 15 meV does not change with excitation power, thus reflecting a genuine feature of few-particle states. Our theoretical model calculations show good agreement with these experimental results. When a prepulse is used to generate a population inversion in the quantum dots, we also observed the effects of nondegenerate biexcitonic correlations in differential transmission.

Spatial Heterogeneity of Biexcitons in Two-Dimensional Ruddlesden–Popper Lead Iodide Perovskites

“…In 2D perovskites, the hot biexciton is likely composed of a 1s exciton at the band edge, and a higher-energy exciton such as a 2s or 2p exciton. Mixed biexcitons such as these were first described in ZnSe, InGaAs, and GaAs, where biexcitons could be formed from a heavy hole exciton and a light hole exciton. They were also observed in CuCl crystals and quantum dots, with transitions from the 1s–1s biexciton to the 1s–2s biexciton observed using infrared transient absorption.…”

Ultrafast biexciton spectroscopy in semiconductor quantum dots: evidence for early emergence of multiple-exciton generation

“…The above mentioned photo-physical complexity of MEG is largely due to the nature of intrinsic multi-particle (or multi-exciton) interaction 28 . When more than two excitons are created under high-energy excitation condition, the lowest lying energy state is not the single exciton; the mutual interaction between two excitons results in the formation of a Coulomb-correlated two excitonic state, called biexciton 29 30 31 32 33 . The biexciton is energetically more stable than the single exciton such that it exists below the single-exciton state 32 34 .…”

Induced absorption dynamics in quantum dot based waveguide electroabsorbers

“…5 Similar experiments with InAs/ GaAs QDs in the range of 970 nm attributed induced absorption to the formation of a nondegenerate biexciton state. 6 More recently, experiments at 1100 nm reported on anomalous induced absorption at the InAs QD ES at high current densities and time-dependent energy level shifts due to Coulomb carrier-carrier interactions. 7 In this letter, the nonlinear recovery of QD based reversed-biased waveguide absorbers is analyzed using a two-color heterodyne pump-probe technique.…”

“…6 In addition, below band gap absorption measurements have suggested that absorptive bound to continuum transitions play an important role in QD laser structures. 10 In order to reproduce the experimental timescales with our model, we note that each of these effects can be simply represented as an increased ES probe absorption which is proportional to the occupational probability g ͑t͒ of the pumped GS.…”