Coulomb effects in type-II Ga(As)Sb quantum dots

We present a detailed explanation of the blue-shift that is observed in Ga(As)Sb quantum dots (QD) with increasing pump power density by employing an 8-band k p model with the Coulomb attractive potential added into the Hamiltonian. Two types of structures are considered: Ga(As)Sb QDs in a GaAs matrix and the same dots overgrown with an InGaAs quantum well (QW). We show that with increasing charge density the electron and hole energy levels shift relative to each other, which results in an increase of the optical transition energy (i.e. a blue-shift). The major contribution to the effect arises from the holes and is a result of their 3D confinement inside the dot. Additionally, with increasing charge density the electrons move closer to the dot, which improves the oscillator strength of the ground-state optical transition.