Abstract

The new Coronavirus or Covid-19 has already became a world-wide pandemic. As of April 22nd, 2020, there are more than 2593129 confirmed case and 179725 total deaths. To fight against the Coronavirus, tremendous efforts have been made for slowing down the spread, such as social distancing. Recently, deep-ultraviolet (DUV) light-emitting diodes (LEDs) are demonstrated to be super effective to deactivate the virus/bacteria. In addition, the outstanding properties such as long life-time, compact size and environmental-friendly from DUV LEDs make them ideal for protecting people from the Coronavirus. However, all AlGaN-based DUV LEDs suffers from low external quantum efficiency issue. Among all the determinants, optical polarization significantly influences internal quantum efficiency and light extraction efficiency from the devices. In this work, we theoretically investigated the impact of the optical polarization properties on DUV LED device efficiencies by using a self-consistent 6-band k·p model and a finite-difference time-domain (FDTD) software. The factors influencing optical polarization switching are also examined and verified. In addition, this work proposed and demonstrated a novel delta-quantum well (QW) design to engineer the optical polarization from the active region. The molecular beam epitaxy (MBE)-grown AlGaN-delta-GaN structure in this study shows an extremely high 85% internal quantum efficiency at 255 nm on a conventional AlN/sapphire substrate, which indicates the delta-QW design is promising for efficient DUV LEDs. Furthermore, several other techniques, such as top-down nanowire arrays, sphere current spreading LEDs, AlGaN substrate and microsphere arrays, are also developed to further improve device efficiency.

Library of Congress Subject Headings

Light emitting diodes--Design and construction; Light emitting diodes--Energy consumption; Quantum electrodynamics

Publication Date

4-22-2020

Document Type

Dissertation

Student Type

Graduate

Degree Name

Microsystems Engineering (Ph.D.)

Department, Program, or Center

Microsystems Engineering (KGCOE)

Advisor

Jing Zhang

Advisor/Committee Member

Seth Hubbard

Advisor/Committee Member

Stefan F. Preble

Campus

RIT – Main Campus

Plan Codes

MCSE-PHD

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