Structural and Optical Properties of InGaN/GaN Vertical Light Emitting Diodes from Flat and Patterned Sapphire Substrates
- 발행기관 아주대학교
- 발행년도 2014
- 제출일 2014-06-27
- 학위수여년월 2014. 8
- 학위명 석사
- 학과 일반대학원 전자공학과
- 실제URI http://www.dcollection.net/handler/ajou/000000017501
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
In this thesis, I report the structural and optical properties of InGaN/GaN VLED that were grown on two kinds of sapphire substrates in which one is a hexagonal array of hemispherical patterns and the other is flat substrate by low-pressure metal-organic chemical vapor deposition (MOCVD). The VLED structures on Cu carriers are fabricated by using electroplating and laser lift-off (LLO) processes. A photoluminescence (PL) intensity comparison of the VLED on two substrates before and after LLO process was presented. The PL properties of VLED grown on PSS have significant advantage compared with the one on FSS. After removing the substrates, defect distribution in the GaN layers lifted-off from flat sapphire substrate (FSS) and patterned sapphire substrates (PSS) has been investigated by using low temperature KOH selective wet etching and cathodoluminescence (CL) mapping. The GaN lifted-off from PSS (GaN-PSS) even though suffers from a higher laser irradiation but it still indicates a higher CL intensity and more uniform emission than the GaN lifted-off from FSS (GaN-FSS). It means that GaN-FSS has higher defect density and deeper defect distribution than the other.
more목차
CONTENTS
ACKNOWLEDGEMENTS
ABSTRACT
CONTENTS
LIST OF FIGURES
LIST OF TABLES
Chapter 1. INTRODUCTION
Chapter 2. BACKGROUND
2.1. Basics of Light Emitting Diodes
a. History of Blue LEDs
b. Principle of LED
c. Patterned Sapphire Substrate
2.2. GaN Material
a. III-Nitrides Properties
b. Structural Defects in GaN
2.3. Characterization techniques
a. Laser Lift-Off Process
b. Photoluminescence
c. Cathodoluminescence
Chapter 3. EXPERIMENT PROCEDURE
3.1. Vertical LED Structure and Processing
3.2. Chemical Wet Etching
3.3. PL and CL Measurement
Chapter 4. RESULTS AND DISCUSSION
4.1. Structural and Optical properties of InGaN/GaN VLED on FSS and PSS
4.2. Defects distribution in the GaN layer lifted-off from FSS and PSS
Chapter 5. CONCLUSION
References
