将多层黑磷集成到光导天线中用于太赫兹辐射
Integration of multi-layer black phosphorus into photoconductive antennas for THz emission
摘要：
我们报告的制造，表征和建模的光导天线使用40 nm的薄膜片的黑磷（BP）作为光电导体和六方氮化硼（hBN）作为覆盖层，以防止氧化的BP。在氧化的高电阻率Si衬底上制造偶极天线，并且将BP和hBN薄片拾取并转移到氮气手套箱内的天线上。转移矩阵技术用于优化BP和hBN的厚度以获得最大吸收。BP薄片沿着天线的阳极-阴极间隙与扶手椅轴对齐，使用反射各向异性测量晶体取向。在780和1560 nm处用100 fs脉冲照射下的光电流成像显示出偏置依赖的最大光电流定位于天线间隙，在780（1560）nm处激发的线性偏置区域中峰值光电导为1（2）S/cm。偏置中的光电流饱和（泵注量）发生在约1 V（0.25 mJ/cm $^2$）。器件性能的数值模拟通过求解麦克斯韦方程组和漂移扩散方程，以获得响应于脉冲激光激发的光电流密度，这在很大程度上是在定性与实验观察。从表面电流密度计算的THz输出表明，BP THz PCA性能至少与基于低温生长GaAs的更传统的器件相当。这些设备代表了使用BP的高性能THz光电导天线的一步。
英文摘要：
We report the fabrication, characterization, and modeling of photoconductive antennas 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.
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