Excitonic fine structure splitting in type-II quantum dots

TL;DR

This paper theoretically investigates excitonic fine structure splitting in type-II InAs quantum dots with GaAsSb capping layers, showing how morphology tuning can minimize splitting for quantum communication applications.

Contribution

It demonstrates that small fine structure splitting values are achievable in type-II quantum dots through morphology control, despite elongation and piezoelectric effects.

Findings

Splitting can be minimized to near natural linewidth levels.

Morphology tuning via capping layer thickness effectively controls splitting.

Oscillator strength remains high, suitable for quantum communication.

Abstract

Excitonic fine structure splitting in quantum dots is closely related to the lateral shape of the wave functions. We have studied theoretically the fine structure splitting in InAs quantum dots with a type-II confinement imposed by a GaAsSb capping layer. We show that very small values of the fine structure splitting comparable with the natural linewidth of the excitonic transitions are achievable for realistic quantum dot morphologies despite the structural elongation and the piezoelectric field. For example, varying the capping layer thickness allows for a fine tuning of the splitting energy. The effect is explained by a strong sensitivity of the hole wave function to the morphology of the structure and a mutual compensation of the electron and hole anisotropies. The oscillator strength of the excitonic transitions in the studied quantum dots is comparable to those with a type-I confinement which makes the dots attractive for quantum communication technology as emitters of polarization-entangled photon pairs.