University of Illinois Urbana-Champaign

Absolute internal quantum efficiency of indium-gallium nitride based light-emitting diodes

Chiu, Yu-Chieh

This item's files can only be accessed by the Administrator group.

Permalink

https://hdl.handle.net/2142/117592

Description

Title
Absolute internal quantum efficiency of indium-gallium nitride based light-emitting diodes
Author(s)
Chiu, Yu-Chieh
Issue Date
2022-12-05
Director of Research (if dissertation) or Advisor (if thesis)
Bayram, Can
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
  • Internal quantum efficiency
  • Light-emitting diode
  • Photonics
  • III-nitride
Abstract
This thesis presents a method to the reveal the absolute internal quantum efficiency of InGaN-based light-emitting diodes (LEDs). InGaN-based light emitting diodes are the backbone of modern high efficiency solid-state lighting, with emerging applications in areas such as next-generation displays for augmented and virtual reality (AR/VR), visible light communications, and bio-optoelectronics. Out of all the quantitative metrics used to characterize LEDs, efficiency is one of the key metrics. State-of-art blue LEDs reach >70% power conversion efficiency from electrical to optical power, but continual improvements are needed to achieve the Department of Energy’s projected efficiency goals, allowing for more energy and CO2 emission savings. Internal quantum efficiency (IQE) is one of many constituent efficiency metrics; it sets the upper-bound of efficiency and is affected by material quality (e.g. defect density) and stack design (e.g. layer thickness). Despite the importance of IQE, there are challenges and possibly erroneous assumptions with current techniques used to measure it. This thesis will first provide an overview of LEDs, including operational principles, efficiency metrics, and a need for an absolute efficiency metric. Next, the theoretical formulation of the method to determine the absolute IQE is discussed, followed by a brief interlude on experimental setup. The structural properties of the LEDs are studied via optical, scanning electron, and atomic force microscopies, X-Ray diffraction, and Raman spectroscopy. Next, optical (via temperature-, time- and power- dependent photoluminescence) properties of InGaN-based blue LEDs are coupled with a channel-based recombination model, to determine the absolute IQE of the LEDs and correlate with their respective structural properties.
Graduation Semester
2022-12
Type of Resource
Thesis
Copyright and License Information
Copyright 2022 Yu-Chieh Chiu

Owning Collections

Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois