關(guān)鍵詞: AlGaN; 深紫外LED; 內(nèi)量子效率; 光提取效率; 電光轉(zhuǎn)換效率
中圖分類(lèi)號(hào): O734 文獻(xiàn)標(biāo)識(shí)碼: A 文章編號(hào): 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(dǎo)體材料，是第三代半導(dǎo)體材料中的典型代表之一。通過(guò)改變AlGaN材料中的組分，可以連續(xù)調(diào)節(jié)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(guò)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(zhì)，未來(lái)會(huì)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(zhǎng)不可調(diào)諧，只能應(yīng)用在一些特殊場(chǎng)景，不適合大規(guī)模日常使用。因此，急需發(fā)展基于半導(dǎo)體AlGaN 材料的固態(tài)紫外光源。基于AlGaN 的深紫外LED 在很多領(lǐng)域具有巨大的應(yīng)用前景，如水、空氣凈化、表面殺菌消毒、光存儲(chǔ)、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(cè)等［1］，如圖1 所示。特別是在殺菌消毒應(yīng)用方面，因?yàn)樾鹿谝咔榈脑颍鞣N深紫外線殺菌消毒市場(chǎng)應(yīng)用需求不斷增長(zhǎng)，為深紫外LED 的開(kāi)發(fā)利用提供了千載難逢的機(jī)遇。根據(jù)法國(guó)Yole 公司的市場(chǎng)調(diào)研報(bào)告，未來(lái)幾年，深紫外LED 的市場(chǎng)規(guī)模將會(huì)呈現(xiàn)指數(shù)級(jí)增長(zhǎng)，到2025 年有望達(dá)到千億級(jí)規(guī)模。深紫外LED 擁有如此巨大的市場(chǎng)應(yīng)用前景，但目前AlGaN 基深紫外LED 的發(fā)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(yuǎn)遜于InGaN 基藍(lán)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(zhàn)需要研究人員去解決。