Date of Award

2010

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Applied Physics & Instrumentation

First Advisor

Dr. Guillaume Huyet

Abstract

In this thesis the novel self-assembled quantum dots based on GaSb/GaAs technology are investigated for the possible application in the near- and mid-infrared, i.e. telecommunication networks, solar cells, gas sensors and imaging systems. These heterostructures exhibit a type-Il band alignment, which means that one species of carriers is confined to the dot, while the other is outside in the surrounding matrix. This physical separation of carriers leads to profound Coulomb interactions, which makes the optical properties of these structures dependent on the injected charge density. The relationship between two of those properties, the emission energy and transition probability, leads to an intricate and complex emission dynamic.

The mechanism responsible for this behavior is investigated by employing experimental and theoretical techniques on several structures that provide diverse confinement scenarios, i.e. where the electrons are confined in the dot and holes are outside as well as an alternate situation. The experiment is based on time-resolved photo- luminescence, which allows for a simultaneous observation of spectral and temporal evolution of the emission. The results are then corroborated with a self-consistent model based on an 8-band k-p formalism, which provides an explanation for the observable features.

For comparison, a novel type-I InAs/GaAs quantum dot system design based on a tunnel injection scheme is investigated under a high-excitation regime, where it also exhibits an interesting emission dynamics that involves an inhibition of the optical transition probability in a charged quantum dot.

Comments

Thesis prepared in association with Tyndall National Institute - Photonic Device Dynamics.

Submitted to Cork Institute of Technology June 2010.

Access Level

info:eu-repo/semantics/openAccess

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