Dissertation Defense

Electron Dynamics of TiN and InGaN/GaN Dot-in-Nanowires

Heather George


This work explores the ultrafast electron dynamics of two materials of emerging importance to
optoelectronics: Titanium Nitride (TiN) and InGaN dot-in-nanowire structures. TiN is a refractory conductive ceramic that has many uses in plasmonics, CMOS electronics, and hot carrier devices. Its optical properties as revealed by ellipsometry are very similar to those of noble metals, which are the most important traditional plasmonic materials; however, its thermal properties and electron-phonon coupling are quite different. Using pump-probe experiments, the transient carrier dynamics are explored. The results are interpreted using a two temperature model which reveals important contrasts to the noble metals.

A selective area sample of InGaN dot-in-nanowires grown on GaN/sapphire were investigated. This type of growth is very controlled and slow compared to self-assembled nanowires, but this also allows the wires to be more homogenous. Even with this type of growth, defects and trap states place a major role in determining the performance of optoelectronic devices such as LEDs, lasers, and detectors. The lifetimes captured give an understanding of the states in the interaction, as well as energy loss to phonons. This work can inform future growth and optimization for nanowire LED and laser applications.

Sponsored by

Professor Ted Norris