Coulomb-induced emission dynamics and self-consistent calculations of type-II Sb-containing quantum dot systems

This paper investigates the effects of Coulomb interactions on the emission dynamics of Sb-containing quantum dot (QD) systems under high excitation densities. Two different type-II confinements are studied: confined electrons with unconfined holes using InAs/GaAs QDs capped with a GaAsSb quantum well (type-IIa), and confined holes with unconfined electrons using GaSb/GaAs QDs capped with an InGaAs quantum well (type-IIb). Time-resolved photoluminescence experiments are compared with self-consistent numerical calculations using an 8-band k.p model. In both structures, we observe a significant blueshift of emission and wavelength-dependent radiative lifetimes, but with marked quantitative differences between the two systems: in the type-IIa, the blueshift is 12 meV with a change in lifetime from 1.4 ns to 2.0 ns, and in the type-IIb, the blueshift is 63 meV with lifetime change from 100 ps to 23 ns. We present a comprehensive explanation of all the important features of the experimental data in terms of Coulomb-induced changes to the carrier wave functions and confining potentials, with the separate confinement of the electrons and holes being a crucial factor.