Integration of multi-layer black phosphorus into photoconductive antennas for THz emission
Integration of multi-layer black phosphorus into photoconductive antennas for THz emission
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DOI：
10.1063/5.0016370
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发表时间：
2020-07
影响因子：
3.2
通讯作者：
M. Doha;J. Santos Batista;A. F. Rawwagah;J. Thompson;A. Fereidouni;K. Watanabe;T. Taniguchi;M. El-Shenawee;H. Churchill
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文献类型：
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作者：
M. Doha;J. Santos Batista;A. F. Rawwagah;J. Thompson;A. Fereidouni;K. Watanabe;T. Taniguchi;M. El-Shenawee;H. Churchill
我们报道了使用40 nm黑磷（BP）薄膜片作为光导体，六方氮化硼（hBN）作为防止BP氧化的覆盖层的光导天线（PCAs）的制造，表征和建模。偶极子天线是在氧化的高电阻率Si衬底上制作的，BP和hBN薄片在氮气手套箱中被拾取并转移到天线上。利用转移矩阵技术优化了BP和hBN的厚度，以获得最大的吸收。BP薄片沿天线的阳极-阴极间隙沿扶手椅轴排列，利用反射各向异性测量晶体取向。在780 (1560)nm处，100fs脉冲照明下的光电流成像显示，在780 (1560)nm处激发的线性偏置条件下，最大光电流与偏置相关，位于天线间隙处，峰值光电导率为1 (2)S/cm，偏置（泵浦流量）下的光电流饱和发生在约1 V （0.25 mJ /cm 2）。通过求解麦克斯韦方程组和漂移扩散方程对器件性能进行了数值模拟，得到了响应脉冲激光激励的光电流密度，与实验结果在定性上基本一致。从表面电流密度计算的太赫兹输出表明，BP太赫兹PCA的性能至少可以与基于低温生长的GaAs的传统器件相媲美。这些装置代表了向使用BP的高性能太赫兹光导天线迈出的一步。
We report the fabrication, characterization, and modeling of photoconductive antennas (PCAs) using 40 nm thin-film flakes of black phosphorus (BP) as the photoconductor and hexagonal boron nitride (hBN) as a capping layer to prevent oxidation of BP. Dipole antennas were fabricated on oxidized high-resistivity Si substrates, and BP and hBN flakes were picked up and transferred onto the antenna inside a nitrogen glovebox. The transfer matrix technique was used to optimize the thickness of BP and hBN for maximum absorption. BP flakes were aligned with the armchair axis along the anode–cathode gap of the antenna, with crystal orientation measured using reflection anisotropy. Photocurrent imaging under illumination with 100 fs pulses at 780 and 1560 nm showed a bias-dependent maximum photocurrent localized to the antenna gap with a peak photoconductivity of 1 (2) S/cm in the linear regime of bias for excitation at 780 (1560) nm. Photocurrent saturation in bias (pump fluence) occurred at approximately 1 V ( 0.25 mJ / cm 2). Device performance was modeled numerically by solving Maxwell’s equations and the drift–diffusion equation to obtain the photocurrent density in response to pulsed laser excitation, which was largely in qualitative agreement with the experimental observations. THz output computed from surface current density suggests that BP THz PCA performance is at least comparable to more traditional devices based on low-temperature-grown GaAs. These devices represent a step toward high-performance THz photoconductive antennas using BP.