摘要
日盲紫外探测器以其较高的探测灵敏度和较低的背景噪声广泛应用于导弹制导、空间安全通信、臭氧层空洞监测和火焰检测等军事和民用领域。氧化镓(Ga_(2)O_(3))是一种典型的超宽禁带半导体材料,其较大的禁带宽度(4.2~5.3 eV)几乎占据太阳光谱的整个日盲波段,被认为是制备日盲紫外探测器的理想材料。主要介绍了Ga_(2)O_(3)。的不同晶体结构和基本特性,并综述了基于多种Ga_(2)O_(3)。结构的日盲紫外探测器的研究进展。基于Ga_(2)O_(3)。纳米线的器件的最大光响应度R>10^(3)A/W,外量子效率能达到10^(5)%;Ga_(2)O_(3)单晶器件的光响应度高达10^(3)~10^(5)A/W,外量子效率超过10^(6)%,响应速度较快(μs级)。Ga_(2)O_(3)基异质结、p-n结和肖特基结的日盲探测器表现出的自驱动特性使其在无需外加电源条件下就能正常工作,这在特殊环境下具有较大的应用潜力。
Significance The sunlight with a wavelength shorter than 280nm cannot penetrate the atmosphere and reach the surface of the earth,for which the 200--280nm waveband is typically referred to as solar-blind region.In recent years,solar-blind ultraviolet photodetectors are widely used in military and civil fields such as missile guidance,space secure communications,ozone hole detection,and flame monitoring due to the advantages of low background noise and high sensitivity.In recent years,the studies of solar-blind ultraviolet photodetectors have mainly focused on wide-bandgap semiconductor materials such as AlxGa1-xN,MgxZn1-xO,and Ga2O3.The bandgap of AlxGa1-xN and MgxZn1-x O is located in the solar-blind region mainly by adjusting the relative composition of Al and Mg.Owning to the relatively high adhesion coefficient and low surface mobility of Al atoms,AlxGa1-xN with high Al content will lead to a larger dislocation density of the epitaxial layer,while phase segregation phenomena are often present for Mgx Zn1-xO with high Mg contents.These factors will lead to poor device performance.Ga2O3is a representative ultrawide bandgap semiconductor material,with a typical band ranging from 4.2to 5.3eV that almost occupies the entire solar-blind region of the solar spectrum.The relatively large bandgap renders it as an ideal candidate for solar-blind ultraviolet detection application.Thanks to the rapid advances in materials synthesis technique,we has witnessed a significant progress in solar-blind ultraviolet photodetectors based on Ga2O3in the past decade.By this token,it is necessary to summarize the recent advances,which may be beneficial for bringing out new highperformance devices with new geometries.Progress In the past few years,various fabrication technologies have been widely adopted to synthesize Ga2O3materials with different crystal structures.For example,in 2004,theβ-Ga2O3single crystals of 1inch(1inch=2.54cm)in diameter have been successfully grown by floating zone for the first time in Japan.Meanwhile,the domestic research on the growth ofβ-Ga2O3single crystals has achieved remarkable results.In 2006,Shanghai Institute of Optics and Fine Mechanics employed the same floating zone to grow theβ-Ga2O3 single crystal.Meanwhile,Tianjin Institute of Electronic Materials has achieved the growth of 2-inchβ-Ga2O3single crystals by using a new edge-defined film-fed growth method in 2018.What is more,various solar-blind ultraviolet photodetectors composed of different forms of Ga2O3 with a variety of device geometries have been investigated.Some effective device optimization approaches such as controlled doping and light manipulation have been introduced to boost the photoresponse of the Ga2O3 based devices.For instance,Sooyeoun et al.from Korea University fabricated the photodetector based on the back-gated field-effect transistor structure using exfoliatedβ-Ga2O3flakes,whose maximum responsivity of the device exceeds104 A/W (Fig.4).Tao′s research group from Shandong University has fabricated the Ga2O3field-effect-transistorbased solar-blind photodetector,its responsivity is up to 105 A/W,and the external quantum efficiency exceeds106%.Besides,our group has reported a catalyst-free vapor-solid growth technique for synthesizingβ-Ga2O3nanowires with single-crystalline quality.The photodetector based onβ-Ga2O3nanowires can operate properly at a large applied bias of 200Vwith the responsivity being enhanced to as high as 103 A/W,and the external quantum efficiency can reach 105%.Fang′s research group from Fudan University has fabricated a high-performance solarblind avalanche photodetector based on highly crystallized ZnO-Ga2O3core-shell heterojunction.The responsivity can reach up to 103 A/W under-10Vbias,and the corresponding external quantum efficiency is as high as 106%[Figs.13(b)--(d)].Moreover,the solar-blind photodetectors based on Ga2O3heterojunction,p-n junction,and Schottky junction with typical self-powered behavior can work normally without external power supply,which might find potential application in special environments.Conclusions and Prospects In summary,we has witnessed extensive progress in Ga2O3 materials and solar-blind ultraviolet photodetectors in the past decade.In respect of material synthesis,the Ga2O3single crystals can be grown at present,and the process route for depositing high-quality and large-area Ga2O3thin films by MOCVD,MBE,magnetron sputtering,and other technologies is mature.Solar-blind photodetectors based on different forms of Ga2O3 have shown superior device performance including high responsivity and external quantum efficiency.What is more,the dark current of the device is as low as 1pA,and the response speed is in the order ofμs.It is believed that the study of Ga2O3 device will mainly focus on the following aspects.First,We need accurately control the size and morphology of Ga2O3 nanomaterials and develop new approach such as doping to reduce the surface state and control internal defects,which is essential for the development of high-performance devices.Second,the effect of defects on crystal quality in single crystals growth,which is an important factor to grow high quality Ga2O3 single crystal,should be extensively studied.Third,the p-type conductivity of Ga2O3 material remains an unsolved problem,which severely limits its application in optoelectronics and power devices.Finally,relevant integration technologies should be developed to solve the problems of device arrangement and assembly.Large area array detectors are to be developed such as focal plane solar-blind imaging systems with the advantages of low power consumption,small size,good compatibility with CMOS readout circuits,and high integration.Additionally,the development of integrated circuit technology that is suitable for Ga2O3related focal plane array is also very important.It is believed that through the continuous efforts in this field,the Ga2O3 based solar-blind ultraviolet photodetectors will be able to be applied to national defense military and civilian fields as soon as possible.
作者
王江
罗林保
Wang Jiang;Luo Linbao(School of Electronic Science and Applied Physics,Hefei University of Technology,Hefei,Anhui 230009,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2021年第11期1-31,共31页
Chinese Journal of Lasers
基金
国家自然科学基金(62074048)
中央高校基础研究基金(JZ2018HGXC0001)
安徽省先进功能材料和器件重点实验室开放基金(4500-411104/011)。
关键词
光电探测器
氧化镓﹔超宽禁带半导体
日盲紫外
光响应
photodetector
gallium oxide
ultra-wide bandgap semiconductor
solar-blind ultraviolet
photoresponse
作者简介
罗林保,E-mail:luolb@hfut.edu.cn。
