Direct demonstration of carrier distribution and recombination within step-bunched UV-LEDs  

作　　者：HOUQIANG XU JIEAN JIANG LI CHEN JASON HOO LONG YAN SHIPING GUO CAI SHEN YANPING WEI HUA SHAO ZI-HUI ZHANG WEI GUO JICHUN YE 

机构地区：[1]Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,Ningbo 315201,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]School of Physical Science and Technology,ShanghaiTech University,Shanghai 201210,China [4]Advanced Micro-Fabrication Equipment Inc.,Shanghai 201201,China [5]Institute of Micro-Nano Photoelectron and Electromagnetic Technology Innovation,School of Electronics and Information Engineering,Hebei University of Technology,Tianjin 300401,China

出　　处：《Photonics Research》2021年第5期764-771,共8页光子学研究（英文版）

基　　金：National Key Research and Development Program of China(2016YFB0400802);National Natural Science Foundation of China(61974149);Key Research and Development Program of Zhejiang Province(2019C01080,2020C01145);Science and Technology Innovation 2025 Major Project of Ningbo(2018B10088,2019B10121);Instrument Developing Project of the Chinese Academy of Sciences(YJKYYQ20190074)。

摘　　要：AlGaN-based solid state UV emitters have many advantages over conventional UV sources. However, UV-LEDs still suffer from numerous challenges, including low quantum efficiency compared to their blue LED counterparts. One of the inherent reasons is a lack of carrier localization effect inside fully miscible AlGaN alloys. In the pursuit of phase separation and carrier localization inside the active region of AlGaN UV-LED, utilization of highly misoriented substrates proves to be useful, yet the carrier distribution and recombination mechanism in such structures has seldom been reported. In this paper, a UV-LED with step-bunched surface morphology was designed and fabricated, and the internal mechanism of high internal quantum efficiency was studied in detail. The correlation between microscale current distribution and surface morphology was provided, directly demonstrating that current prefers to flow through the step edges of the epitaxial layers. Experimental results were further supported by numerical simulation. It was found that efficient radiative recombination centers were formed in the inclined quantum well regions. A schematic three-dimensional energy band structure of the multiple quantum wells(MQWs) across the step was proposed and helps in further understanding the luminescence behavior of LEDs grown on misoriented substrates. Finally, a general principle to achieve carrier localization was proposed, which is valid for most ternary Ⅲ-Ⅴ semiconductors exhibiting phase separation.

关 键 词：distribution mechanism QUANTUM 

分 类 号：TN312.8[电子电信—物理电子学]