Excitonic structure and pumping power dependent emission blue-shift of type-II quantum dots

TL;DR

This paper combines theoretical and experimental approaches to study the excitonic structure of type-II quantum dots, revealing large antibinding energies and explaining emission blue-shifts and spectral broadening related to pumping power.

Contribution

It introduces a comprehensive analysis of multi-particle excitonic effects in type-II quantum dots, explaining phenomena previously not well understood.

Findings

Large antibinding energies in exciton complexes with multiple electrons and holes.

Blue-shift of emission with increasing pumping power.

Significant inhomogeneous spectral broadening observed.

Abstract

In this work we study theoretically and experimentally the multi-particle structure of the so-called type-II quantum dots with spatially separated electrons and holes. Our calculations based on customarily developed full configuration interaction approach reveal that exciton complexes containing holes interacting with two or more electrons exhibit fairly large antibinding energies. This effect is found to be the hallmark of the type-II confinement. In addition, an approximate self-consistent solution of the multi-exciton problem allows us to explain two pronounced phenomena: the blue-shift of the emission with pumping and the large inhomogenous spectral broadening, both of those eluding explanation so far. The results are confirmed by detailed intensity and polarization resolved photoluminescence measurements on a number of type-II samples.