Date of Award

2013

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Applied Physics & Instrumentation

First Advisor

Dr. Guillaume Huyet

Abstract

In the past decades, with the development of low-dimensional semiconductor heterostructures, research has been focused on studying novel materials and proposing new solutions for the improvement and optimization of numerous optoelectronic applications. Examples of these applications include optical data storage, displays and medical diagnostics in the ultraviolet and visible spectral range, or telecommunication networks, solar cells, gas sensing and imaging systems in the near- and mid-infrared. In this thesis, the optical characterization of a number of promising semiconductor nanostructures for the realization of next-generation optoelectronic devices is reported. The optical emission properties of each structure, measured by means of power-dependent and time-resolved photoluminescence experiments, are also corroborated with the corresponding calculated band structure. In InAs1-x Sbx /GaAs quantum dots, the type-1 to type-II band alignment transition is obtained by increasing the Sb concentration in the structure. The conduction band offset can be continuously tuned, and the condition of flat conduction band is achieved when the Sb content in the dots is approximately 60%. In InAs/GaAs quantum dots capped with a GaAs0.86Sb0.14 strain-relieving layer, a type-I ground state and a few type-II excited states coexist in the same structure. Moreover, the complex emission dynamics observed under high-power excitations are explained in terms of the band structure and energy level modifications induced by two competitive carrier interactions inside the material. Finally, in direct band-gap Ge quantum wells strained by fully relaxed In0.30Ga0.70As barriers, the band offsets depend on the termination of the InGaAs layers in contact with the Ge, and lead to different optical transitions characterized by either type-I-like or type-II-like behavior in spatially distinct areas of the heterostructure. This work may provide new strategies and increased flexibility in the design of novel devices, and open up new possibilities for the development of III-V and group-IV photonics.

Comments

Thesis prepared in association with Tyndall National Institute

Access Level

info:eu-repo/semantics/openAccess

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