报告题目: Recent Progress of Efficiency Droop Improvement for High efficiency (>200lm/W) GaN-based Light-Emitting Diodes

　　报告人: Prof. Hao-Chung Kuo (National Chiao-Tung University台湾交通大学)

　　时间: 2013年11月14日(星期四) 上午9:00

　　地点: 中国科学院半导体研究所 图书馆101会议室

　　摘要：GaN-based light-emitting-diodes (LEDs) have been developed in various applications due to its widely tunable wavelength from ultraviolet to blue/green. Although the light-extraction efficiency has been significantly improved by different techniques, the internal quantum efficiency (IQE) still suffers a major obstacle, i.e., the substantial decrease in efficiency with increasing injection current. Carrier overflow out of the active region as well as inefficient injection and transportation of holes have been identified to be the major reasons of efficiency droop. Prof. Kuo introduced the physical mechanisms of efficiency droop in GaN-based LEDs and its origin, and proposed several methods to reduce this effect, such as alternative substrates, semi-polar (1-101) MQWs, low temperature insertion layer between n-GaN and MQWs, graded-thickness MQWs (GQWs), and graded-composition EBL (GEBLs). The results show that by reducing the polarization field in MQWS, enhancing hole transportation in MQWs, and enhancing hole injection across EBL, the efficiency droop behavior could be successfully reduced. Finally high efficiency white LED with efficacy >180 lm/W at 3000K was demonstrated.

　　Biography: Hao-Chung Kuo received the B.S. degree in physics from National Taiwan University, the M.S. degree in ECE from Rutgers University, New Brunswick, NJ, in 1995, and the Ph.D. degree in ECE from University of Illinois at Urbana Champaign, in 1999. He has an extensive professional career both in research and industrial research institutions that includes: MTS I in Lucent Technologies, Bell Laboratories (1993–1995); and a Senior R&D Engineer in Fiber-Optics Division at Agilent Technologies (1999–2001) and LuxNet Corporation (2001–2002). Since October 2002, he has been with the National Chiao-Tung University as a Faculty Member of the Institute of Electro-Optical Engineering. He is now the Associate Dean, Office of International Affair, NCTU. His current research interests include semiconductor lasers, VCSELs, blue and UV LED lasers, quantum-confined optoelectronic structures, optoelectronic materials, and Solar cell. He has authored and coauthored more than 400 SCI journal papers (H index 34, citations >5390) and more than 200 international conference papers, 2 invited book chapter, 10 granted and 20 pending patents. Prof. Kuo is IET (UK), OSA (optical Society of America), and SPIE Fellow (2012). He was honored with National Science Council of Taiwan- Dr. Ta-You Wu Award (2007) and the Optical Engineering Society of Taiwan - Yang facility Award (2007).