Type II InAs/GaAsSb quantum dots: Highly tunable exciton geometry and topology

Abstract

External control over the electron and hole wavefunctions geometry and topology is investigated in a p-i-n diode embedding a dot-in-a-well InAs/GaAsSb quantum structure with type II band alignment. We find highly tunable exciton dipole moments and largely decoupled exciton recombination and ionization dynamics. We also predict a bias regime where the hole wavefunction topology changes continuously from quantum dot-like to quantum ring-like as a function of the external bias. All these properties have great potential in advanced electro-optical applications and in the investigation of fundamental spin-orbit phenomena.

Excitonic structure and pumping power dependent emission blue-shift of type-II quantum dots

“…The blue-shift is accompanied by a change of the spatial distribution of the hole wavefunction27, see insets of Fig. 5(b): holes are “squeezed” towards the QD body and, thus, towards the electrons2754.…”

Wave‐Function Topology Effects on Charged Excitons in Type‐II InAs/GaAsSb Quantum Dots and Rings

“…As the hole wave‐function spills over the GaAsSb barrier, the QD becomes a central barrier potential for the hole, and due to strain‐driven localization, the hole gets confined in an effective quantum ring potential and is characterized by a doubly connected wave‐function topology . This transition can be described well in a single particle picture . However, it falls short to predict the magnetic evolution of the different exciton complexes.…”

“…Beyond a Sb concentration , the band alignment between the QD and overlayer material changes, turning into type‐II for the valence band, and further correcting the emission wavelength and radiative lifetime . In this situation, the electron and the hole get localized in different spatial regions building up a vertical and an in‐plane dipole moment . InAs/GaAsSb QDs are thus a good candidate for the observation of optical Aharonov–Bohm effects (OABE), as studied in other systems for neutral and charged exciton complexes .…”

“…As was anticipated before, the interactions involving a hole are highly dependent on d while the electron–electron term remains rather constant. The electron is only influenced by d through the height of the barriers confining it from the top . As the barrier increases, the wave‐functions becomes more localized and therefore J ee weakly increases.…”

“…This change is attributed to a sign‐inversion of the hole g ‐factor induced by the spin–orbit interaction within the valence band. Due to the large dipole moment of these nanostructures, this could be exploited in topology driven g ‐factor tuning schemes using external electric fields …”