关键词: AlGaN; 深紫外LED; 内量子效率; 光提取效率; 电光转换效率
中图分类号: O734 文献标识码: A 文章编号: 1000-985X( 2020) 11-2079-19
Ｒesearch Progress of AlGaN based Deep Ultraviolet Light Emitting Diodes
WU Feng，DAI Jiangnan，CHEN Changqing
( Wuhan National Laboratory for Optoelectronics，Huazhong University of Science and Technology，Wuhan 430074，China)
Abstract: Deep ultraviolet ( DUV) light has a large potential application in sterilization，biochemical detection，UV curving，UV communication，and so on． AlGaN based DUV light emitting diodes ( LEDs) have attracted tremendous attention and research because of their unique advantages such as nontoxicity，small size，low power consumption，long service life and wavelength tunability． After nearly 20 years research and development，the emission efficiency and device lifetime of AlGaN DUV LEDs have been promoted significantly，and some products have been commercialized． However，compared with the GaN based blue LEDs，the efficiency of current AlGaN DUV LEDs is still very low，which means the promotion room is very large for the research community． This paper first introduces the research status of the state-of-art AlGaN DUV LEDs，and analyses the reasons for the low emission efficiency． Then，the recent progresses of the AlGaN DUV LEDs，from the internal quantum efficiency ( IQE) ，light extraction efficiency ( LEE) ，and wall-plug efficiency ( WPE) ，respectively，have been systematically reviewed． The various solutions that improve the efficiencies have been summarized． Finally，the future development directions and possible solutions for the efficiency have been provided．Key words: AlGaN; deep ultraviolet light emitting diode; internal quantum efficiency; light extraction efficiency; wallplug efficiency
AlGaN 是一种宽禁带直接带隙半导体材料，是第三代半导体材料中的典型代表之一。通过改变AlGaN材料中的组分，可以连续调节其禁带大小，从3． 4 eV 到6． 1 eV，覆盖了从210 nm 到360 nm 的紫外波段范围，因此其是制备深紫外LED 的理想材料。过去几十年，深紫外光源主要是由汞灯以及一些气体和固体激光器提供。汞是一种剧毒物质，未来会逐渐被禁止使用，且汞灯体积大、使用不方便、寿命短、能耗高。气体和固体激光器体积大，能耗高、波长不可调谐，只能应用在一些特殊场景，不适合大规模日常使用。因此，急需发展基于半导体AlGaN 材料的固态紫外光源。基于AlGaN 的深紫外LED 在很多领域具有巨大的应用前景，如水、空气净化、表面杀菌消毒、光存储、3D 打印、紫外光刻、非视距通信、气体传感、紫外光疗、油墨固化以及防伪检测等［1］，如图1 所示。特别是在杀菌消毒应用方面，因为新冠疫情的原因，各种深紫外线杀菌消毒市场应用需求不断增长，为深紫外LED 的开发利用提供了千载难逢的机遇。根据法国Yole 公司的市场调研报告，未来几年，深紫外LED 的市场规模将会呈现指数级增长，到2025 年有望达到千亿级规模。深紫外LED 拥有如此巨大的市场应用前景，但目前AlGaN 基深紫外LED 的发光效率依旧很低，其外量子效率( EQE) 和插墙效率( WPE) 普遍低于10%和5%，远逊于InGaN 基蓝光LED，因此，AlGaN 基深紫外LED 的性能还有很大的提升空间，还有许多难题和挑战需要研究人员去解决。