關鍵詞: AlGaN; 深紫外LED; 內量子效率; 光提取效率; 電光轉換效率
中圖分類號: O734 文獻標識碼: A 文章編號: 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 是一種寬禁帶直接帶隙半導體材料，是第三代半導體材料中的典型代表之一。通過改變AlGaN材料中的組分，可以連續調節其禁帶大小，從3． 4 eV 到6． 1 eV，覆蓋了從210 nm 到360 nm 的紫外波段范圍，因此其是制備深紫外LED 的理想材料。過去幾十年，深紫外光源主要是由汞燈以及一些氣體和固體激光器提供。汞是一種劇毒物質，未來會逐漸被禁止使用，且汞燈體積大、使用不方便、壽命短、能耗高。氣體和固體激光器體積大，能耗高、波長不可調諧，只能應用在一些特殊場景，不適合大規模日常使用。因此，急需發展基于半導體AlGaN 材料的固態紫外光源?；贏lGaN 的深紫外LED 在很多領域具有巨大的應用前景，如水、空氣凈化、表面殺菌消毒、光存儲、3D 打印、紫外光刻、非視距通信、氣體傳感、紫外光療、油墨固化以及防偽檢測等［1］，如圖1 所示。特別是在殺菌消毒應用方面，因為新冠疫情的原因，各種深紫外線殺菌消毒市場應用需求不斷增長，為深紫外LED 的開發利用提供了千載難逢的機遇。根據法國Yole 公司的市場調研報告，未來幾年，深紫外LED 的市場規模將會呈現指數級增長，到2025 年有望達到千億級規模。深紫外LED 擁有如此巨大的市場應用前景，但目前AlGaN 基深紫外LED 的發光效率依舊很低，其外量子效率( EQE) 和插墻效率( WPE) 普遍低于10%和5%，遠遜于InGaN 基藍光LED，因此，AlGaN 基深紫外LED 的性能還有很大的提升空間，還有許多難題和挑戰需要研究人員去解決。