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自然科学进展

中国科学基金

Science Foundation in China



Improved performance of GaN-based light-emitting diodes by using short-period superlattice structures
Yi-jung LIU1, Chien-chang HUANG1, Tai-you CHEN1, Chi-shiang HSU1, Shiou-ying CHENG2, Kun-wei LIN3, Jian-kai LIOU1, Wen-chau LIU1
1. Institute of Microelectronics, Department of Electrical Engineering, National Cheng-Kung University, Tainan 70101, Taiwan, China; 2. Department of Electronic Engineering, Nation Ilan University, I-Lan 26041, Taiwan, China; 3. Department and Graduate Institute of Computer Science and Information Engineering, Chaoyang University of Technology, Taichung 41349, Taiwan, China
Abstract:  An InGaN/GaN multiple-quantum-well (MQW) light-emitting diode (LED) with a ten-period i (undoped) -InGaN/p (Mg doped) -GaN (2.5 nm/5.0 nm) superlattice (SL) structure, was fabricated. This SL structure that can be regarded as a confinement layer of holes to enhance the hole injection efficiency is inserted between MQW and p-GaN layers. The studied LED device exhibits better current spreading performance and an improved quality, compared with a conventional one without SL structure. Due to the reduced contact resistance as well as more uniformity of carriers injection, the operation voltage at 20 mA is decreased from 3.32 to 3.14 V. A remarkably reduced reverse-biased leakage current (10?7?10?9 A) and higher endurance of the reverse current pulse are found. The measured output power and external quantum efficiency (EQE) of the studied LED are 13.6 mW and 24.8%, respectively. In addition, significant enhancement of 25.4% in output power as well as increment of 5% in EQE for the studied devices is observed, as the studied devices show superior current spreading ability and reduction in dislocations offered by the SL structure.
Keywords:  GaN; superlattice (SL); current spreading; hole confinement; electrostatic discharge (ESD)
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