Mid-infrared intersublevel absorption of vertically electronically coupled InAs quantum dots

Abstract

We have studied mid-infrared intersublevel absorption of samples containing two layers of vertically self-aligned, self-assembled InAs quantum dots separated by a thin GaAs barrier. Samples with coupled quantum dots exhibiting different average size between the two layers are investigated. The electronically coupled quantum dot absorption is compared with the absorption of a reference sample containing uncoupled quantum dots. Electronically coupled quantum dots present a spectrally narrow absorption line (∼20meV full width at half maximum) mainly polarized along the growth axis in the range 110–150meV. This absorption is attributed to the bound-to-bound transition between bonding (symmetric-like) and antibonding (antisymmetric-like) s state combinations of the double quantum dot structure. This assignment is supported by the electronic structure of the coupled quantum dots as calculated by the three-dimensional resolution of the Schrödinger equation written in the 8-band k.p envelope function formalism.