Ghosh Sayantan, Varghese Abin, Thakar Kartikey, Dhara Sushovan, Lodha Saurabh
Department of Electrical Engineering, IIT Bombay, Mumbai, India.
Department of Materials Science and Engineering, Monash University, Clayton, VIC, Australia.
Nat Commun. 2021 Jun 7;12(1):3336. doi: 10.1038/s41467-021-23679-8.
Layered transition metal dichalcogenides have shown tremendous potential for photodetection due to their non-zero direct bandgaps, high light absorption coefficients and carrier mobilities, and ability to form atomically sharp and defect-free heterointerfaces. A critical and fundamental bottleneck in the realization of high performance detectors is their trap-dependent photoresponse that trades off responsivity with speed. This work demonstrates a facile method of attenuating this trade-off by nearly 2x through integration of a lateral, in-plane, electrostatically tunable p-n homojunction with a conventional WSe phototransistor. The tunable p-n junction allows modulation of the photocarrier population and width of the conducting channel independently from the phototransistor. Increased illumination current with the lateral p-n junction helps achieve responsivity enhancement upto 2.4x at nearly the same switching speed (14-16 µs) over a wide range of laser power (300 pW-33 nW). The added benefit of reduced dark current enhances specific detectivity (D*) by nearly 25x to yield a maximum measured flicker noise-limited D* of 1.1×10 Jones. High responsivity of 170 A/W at 300 pW laser power along with the ability to detect sub-1 pW laser switching are demonstrated.
层状过渡金属二硫属化物因其非零直接带隙、高光吸收系数和载流子迁移率以及形成原子级尖锐且无缺陷的异质界面的能力，在光电探测方面展现出巨大潜力。高性能探测器实现过程中的一个关键且基本的瓶颈是其与陷阱相关的光响应，这种光响应在响应度和速度之间进行权衡。这项工作展示了一种简便方法，通过将横向、面内、静电可调谐的p-n同质结与传统的WSe光电晶体管集成，将这种权衡减弱近2倍。可调谐的p-n结允许独立于光电晶体管调制光载流子数量和导电沟道宽度。横向p-n结增加的光照电流有助于在很宽的激光功率范围（300 pW - 33 nW）内，以几乎相同的开关速度（14 - 16 μs）将响应度提高到2.4倍。暗电流降低的额外好处是将比探测率（D*）提高近25倍，从而产生最大测量值为1.1×10琼斯的闪烁噪声限制D*。展示了在300 pW激光功率下170 A/W的高响应度以及检测低于1 pW激光开关的能力。
