Design, growth and fabrication and characterisation of InGaN Micro Light Emitting Diodes using a Direct Epitaxial Approach

Free standing micro disks have been the focus of a significant amount of research in
recent years. This is due to the ease in creating low threshold micro lasers and micro array
devices. Unfortunately, there are issues with the fabrication process that limit the overall
efficiency and quality of such devices. The top-down approach used with these micro disk
leads to severe sidewall damage from the etching process. Therefore, we present a novel
approach using a direct epitaxial method to selectively grow micro disks in a patterned SiO2
template. This thesis presents the design process in which we made these devices and the
use of characterisation to optimise the method to create highly efficient micro-LEDs.

We also take these devices further and created micro laser cavities using a hybrid
epitaxial/ dielectric cavity. Using lattice matched nanoporous GaN/undoped GaN Distributed Bragg Reflectors (DBR) and a dielectric SiO2/SiN based DBR, we can create optically pumped micro disks arrays with stimulated emission with a wavelength of 510nm.

Finally, we investigate a new limiting factor in the growth of ultra-small micro disks
(<3.5μm) in the form the circularity of the micro disks themselves rather than the roughness
of the sidewall.