Hole subband mixing and polarization of luminescence from quantum dashes: a simple model

TL;DR

This paper presents a simple semi-qualitative model explaining the polarization of luminescence in quantum dashes, emphasizing valence subband mixing and predicting how structural and external factors influence the degree of polarization.

Contribution

It introduces a novel model linking shape asymmetry and valence subband mixing to luminescence polarization, aligning well with experimental data for InAs/InP quantum dashes.

Findings

Model accurately predicts polarization dependence on in-plane dimensions.

Non-monotonic spectral behavior of DOP explained by excited state contributions.

Good agreement with experimental data using realistic parameters.

Abstract

In this paper, we address the problem of luminescence polarization in the case of nanostructures characterized by an in-plane shape asymmetry. We develop a simple semi-qualitative model revealing the mechanism that accounts for the selective polarization properties of such structures. It shows that they are not a straightforward consequence of the geometry but are related to it via valence subband mixing. Our model allows us to predict the degree of polarization (DOP) dependence on the in-plane dimensions of investigated structures assuming a predominantly heavy hole character of the valence band states, simplifying the shape of confining potential and neglecting the influence of the out-of plane dimension. The energy dependence modeling reveals the importance of different excited states in subsequent spectral ranges leading to non-monotonic character of the DOP. The modeling results show good agreement with the experimental data for an ensemble of InAs/InP quantum dashes for a set of realistc parameters with the heavy-light hole states separation being the only adjustable one. All characteristic features are reproduced in the framework of the proposed model and their origin can be well explained and understood. We also make some further predictions about the influence of both the internal characteristics of the nanostructures (e.g. height) and the external conditions (excitation power, temperature) on the overall DOP.