Black phosphorus photoconductive terahertz antenna: 3D modeling and experimental reference comparison
Black phosphorus photoconductive terahertz antenna: 3D modeling and experimental reference comparison
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DOI：
10.1364/josab.419996
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发表时间：
2021-04
影响因子：
1.9
通讯作者：
Jose Santos Batista;H. Churchill;M. El-Shenawee
中科院分区：
文献类型：
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作者：
Jose Santos Batista;H. Churchill;M. El-Shenawee
本文提出了一种以新兴的二维各向异性材料黑磷为半导体层的太赫兹光导天线（PCA）的三维模型。这项工作旨在了解黑磷（BP）在提高传统太赫兹（THz） pca的信号产生和带宽方面的潜力。基于有限元方法，利用COMSOL Multiphysics软件包对三维BP PCA发射极进行建模，采用四个模块：求解麦克斯韦方程组的频域射频模块、计算光电流的半导体模块、计算温度变化的固体传热模块和计算太赫兹辐射电场脉冲的瞬态射频模块。提出的三维模型是计算密集型的，其中PCA装置包括从纳米到微尺度的薄层厚度。通过应用完美的电和磁边界条件来利用结构的对称性，将计算域减少到射频模块中器件的四分之一。结果表明，由偏置电压诱导的电流传导引起的温度变化仅增加了0.162 K。此外，由于飞秒激光源，半导体中的电磁功率耗散温度增加了0.441 K。结果表明，当最大偏置电压为1 V，平均激光功率为1 mW时，温度变化导致光电流峰值分别增加了~ 3.4%和~ 10%。虽然模拟天线的有源区域为光学和半导体响应提供了准确的结果，但模拟热效应对光电流的影响需要更大的计算域，以避免温度的虚假上升。最后，与参考商用LT-GaAs PCA的测量脉冲相比，模拟的太赫兹信号产生电场脉冲的带宽有增加的趋势。增强信号产生和带宽将改善太赫兹成像和光谱用于生物医学和材料表征应用。
This paper presents a 3D model of a terahertz photoconductive antenna (PCA) using black phosphorus, an emerging 2D anisotropic material, as the semiconductor layer. This work aims at understanding the potential of black phosphorus (BP) to advance the signal generation and bandwidth of conventional terahertz (THz) PCAs. The COMSOL Multiphysics package, based on the finite element method, is utilized to model the 3D BP PCA emitter using four modules: the frequency domain RF module to solve Maxwell’s equations, the semiconductor module to calculate the photocurrent, the heat transfer in solids module to calculate the temperature variations, and the transient RF module to calculate the THz radiated electric field pulse. The proposed 3D model is computationally intensive where the PCA device includes thin layers of thicknesses ranging from nano- to microscale. The symmetry of the configuration was exploited by applying the perfect electric and magnetic boundary conditions to reduce the computational domain to only one quarter of the device in the RF module. The results showed that the temperature variation due to the conduction of current induced by the bias voltage increased by only 0.162 K. In addition, the electromagnetic power dissipation in the semiconductor due to the femtosecond laser source showed an increase in temperature by 0.441 K. The results show that the temperature variations caused the peak of the photocurrent to increase by ∼3.4% and ∼10%, respectively, under a maximum bias voltage of 1 V and average laser power of 1 mW. While simulating the active area of the antenna provided accurate results for the optical and semiconductor responses, simulating the thermal effect on the photocurrent requires a larger computational domain to avoid false rise in temperature. Finally, the simulated THz signal generation electric field pulse exhibits a trend in increasing the bandwidth of the proposed BP PCA compared with the measured pulse of a reference commercial LT-GaAs PCA. Enhancing signal generation and bandwidth will improve THz imaging and spectroscopy for biomedical and material characterization applications.