摘要
高灵敏度、可室温下工作的太赫兹(THz)探测器是太赫兹在生物技术、量子传输、通信、成像等领域得以应用的关键。本文报道了一种石墨烯太赫兹探测器设计方法,该探测器通过将蝶形天线与石墨烯pn结构建至一个器件中,利用蝶形金属天线将波长为110 mm(2.7 THz)的太赫兹远场光汇聚至约800 nm的石墨烯THz吸收层,同时将这蝶形天线的两极设计为两个独立栅极,将800 nm的吸收层转变为可分离光电子的pn结区,通过增强局域光场增加太赫兹吸收,并同时增强光电子分离效率,将正交极化方向的消光比提升了1到2个数量级,在室温下实现了较低的噪声等效功率(NEP)~1 nW·Hz^(−1/2)。这一设计为太赫兹探测提供了新的技术路径。
In electromagnetic spectrum,terahertz(THz)wave is between light and microwave.Its photon energy is much lower than normal infrared light and its frequency is higher than microwave.Therefore,it is hard to implement techniques of these two spectral ranges into THz spectrum,especially techniques in generation,modulation and detection.This has hindered the exploitation of THz spectrum although recent studies have showed its promising potentials in industries such as semiconductors,biotechnology,communications,imaging and so on.In THz detection,it is critical to have detectors with high response speed,high sensitivity and capability of operating at room temperature.In this study,we have designed a bow-tie antenna and integrated it into a graphene photodetector.By simulating with finite element analysis,we optimize the total length of the bow-tie antenna as about 50μm and a gap of about 800 nm in the middle in order to target at 2.7 THz wave.By design,the antenna localizes the THz radiation to the narrow gap and enhances the local electric field by more than 20 times.Inside the same narrow gap,we build a graphene pn junction by applying different voltages on the two halves of the antenna,which also function as two independent gate electrodes in the device.In this device geometry,the absorption enhancement region overlaps with photocarrier separation regions in graphene,which therefore greatly increases photocurrent generation as firstly reported in Ref.25.In addition to the antenna,we also design the channel.Firstly,we use BN-encapsulated graphene which has shown low residual doping(residual doping concentration of 1.3×10^(11) cm^(−2))and high mobility(μup to 20000 cm2·V^(−1)·s^(−1) at room temperature)in the device.The high-quality graphene as channel guarantees a large seeback-coefficient difference at the pn junction and fast photoresponse.Secondly,the channel width at the antenna gap is reduced for further increasing the electron temperature and photocarrier-separating efficiency.Whereas the channel width at the contact is maintained for decreasing the contact resistance.With the antenna and channel design in an as-fabricated device,the photocurrent is enhanced by up to 2 orders of magnitude when the polarization of incident wave coincides with the optimized polarization of the antenna.The corresponding noise equivalent power(NEP)is calculated as about 1 nW·Hz^(−1/2)if Johnson-Nyquist noise is assumed as the dominating noise.Moreover,the operating frequency is measured as larger than 5 kHz,which,together with the enhanced photoresponse,indicates that our design is a promising candidate for THz detection.
作者
杨嘉炜
郑春阳
庞亚会
纪仲阳
李雨芮
胡嘉仪
朱江瑞
陆琪
林立
刘忠范
胡清梅
关宝璐
尹建波
Jiawei Yang;Chunyang Zheng;Yahui Pang;Zhongyang Ji;Yurui Li;Jiayi Hu;Jiangrui Zhu;Qi Lu;Li Lin;Zhongfan Liu;Qingmei Hu;Baolu Guan;Jianbo Yin(Faculty of Information Technology,Beijing University of Technology,Beijing 100124,China;Beijing Graphene Institute,Beijing 100095,China;Academy for Advanced Interdisciplinary Studies,Peking University,Beijing 100871,China;Department of Electronics,Peking University,Beijing 100871,China;College of Science,China University of Petroleum(Beijing),Beijing 102249,China;School of Materials Science and Engineering,Peking University,Beijing 100871,China;College of Chemistry and Molecular Engineering,Peking University,Beijing 100871,China.)
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2023年第10期125-133,共9页
Acta Physico-Chimica Sinica
基金
国家重点研发计划(2020YFA0308900)
国家自然科学基金(T2188101,52072043,60908012,61575008,61775007)
北京市自然科学基金(4172011)资助项目。
