Geometrical-confinement effects on excitons in quantum disks

TL;DR

This paper investigates how the shape and size of elliptical quantum dots influence exciton properties and optical responses, revealing size-dependent blue shifts and spectral peak splitting due to geometrical confinement.

Contribution

It provides a detailed numerical analysis of exciton behavior in elliptical quantum disks, highlighting the impact of geometry on optical properties and comparing results with experimental spectra.

Findings

Strong blue shift of luminescence in nm-sized dots due to geometry

Transition peaks split and shift to higher energy in elliptical dots

Comparison with experimental photoluminescence spectra confirms theoretical predictions

Abstract

Excitons confined to flat semiconductor quantum dots with elliptical cross section are considered as we study geometrical effects on exciton binding energy, electron-hole separation, and the resulting linear optical properties. We use numerical matrix diagonalization techniques with appropriately large and optimized basis sets in an effective-mass Hamiltonian approach. The linear optical susceptibilities of GaAs and InAs dots for several different size ratios are discussed and compared to experimental photoluminescence spectra obtained on GaAs/AlGaAs and InAs/GaAs quantum dots. For quantum dots with several nm in size, there is a strong blue shift of the luminescence due to geometrical confinement effects. Also, transition peaks are split and shifted towards higher energy, in comparison with dots with circular cross sections.