Interplay of Electrical, Mechanical and Thermal Fields in III-N Nanostructures for LED Applications

Author

Krishna Kumari Yalavarthi, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2013

Degree Name

Doctor of Philosophy

Department

Electrical and Computer Engineering

First Advisor

Ahmed, Shaikh

Abstract

This work aims at exploring the competing effects of various internal/built-in fields on the electronic structure and optical properties of III-N nanostructured (Quantum Dots and disk-in-a-wire) LEDs using a multiscale modeling approach. The objective is three-fold: (1) calculate the strain distribution, optical transition rates and one-particle electronic states using a 10-band sp3s* tight-binding framework; (2) to compute the effects of piezoelectric and pyroelectric polarization on the optical transition rates; (3) to model piezoelectricity in the wurtzite lattice, we have considered four different polarization models (based on the experimental /bulk and ab initio coefficients) in increased order of accuracy; (4) to study the origin and effects of these four competing internal fields on the electronic structure of self-assembled InN/GaN quantum dots having three different geometries, namely, box, dome, and pyramid; (5) integrating the NEMO3-D with commercial TCAD tool Synopsys to determine the terminal electrical and optical characteristics of InGaN/GaN disk-in-a-wire LEDs; and (6) finally to propose optimum device specifications for InGaN/GaN disk-in-a-wire LEDs to achieve maximum Internal Quantum Efficiency (IQE).