InGaN QD Microdisks: Experiments in Fabrication and Emission Enhancement

Abstract

Gallium nitride (GaN) is a material with outstanding electrical and optical properties. With it's high heat capacity and thermal conductivity, GaN has demonstrated its potential in high power electronic devices such as transistors. GaN material embedded with indium gallium nitride (InGaN) quantum dots (QDs) allows for room temperature emission from the blue region of the visible spectrum. InGaN QD material has been used to create highly efficient light emitting diodes and nanolasers. In spite of these unique and advantageous properties, realising devices with GaN can present many challenges. GaN material is notoriously difficult to process, often riddled with defects that make device fabrication difficult and affect the overall efficiency of the device. Further, the InGaN QD system is not trivial to grow and as a result there has been less characterization of this system in comparison to other QD systems. This thesis seeks to provide further insight into the InGaN QD system and the fabrication of InGaN QD microdisks with high densities of threading dislocations (TDs). Through further characterisation of this system, we may be able to contribute some understanding as to why InGaN behaves in the way it does and how we might overcome processing limitations. Chapter one provides further motivation as to why we are interested in creating devices from this material and presents some of the past literature on GaN and InGaN devices. Chapter two, sets the groundwork for important concepts and theories on which we base our device design and experiments. The materials to be used throughout this thesis are introduced, as well as the microdisk fabrication process. Chapter three describes a series of photoelectrochemical etch experiments using an InGaN material with a high TD density. Finally, chapter four includes further experimentation with InGaN microdisks; probing the potential for InGaN and 2D materials with experiments on the use of 2D MoS2 for enhanced emission from InGaN QD microdisks.