Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States.
Department of Material Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
Nano Lett. 2021 Dec 8;21(23):9838-9844. doi: 10.1021/acs.nanolett.1c03665. Epub 2021 Nov 18.
Photodetectors fabricated from low-dimensional materials such as quantum dots, nanowires, and two-dimensional materials show tremendous promise based on reports of very high responsivities. However, it is not generally appreciated that maximizing the internal gain may compromise the detector performance at low light levels, reducing its sensitivity. Here, we show that for most low-dimensional photodetectors with internal gain the sensitivity is determined by the junction capacitance. Thanks to their extremely small junction capacitances and reduced charge screening, low-dimensional materials and devices provide clear advantages over bulk semiconductors in the pursuit of high-sensitivity photodetectors. This mini-review describes and validates a method to estimate the capacitance from external photoresponse measurements, providing a straightforward approach to extract the device sensitivity and benchmark against physical limits. This improved physical understanding can guide the design of low-dimensional photodetectors to effectively leverage their unique advantage and achieve sensitivities that can exceed that of the best existing photodetectors.
基于高响应率的报道，由量子点、纳米线和二维材料等低维材料制成的光电探测器具有巨大的应用潜力。然而，人们通常没有意识到，最大化内部增益可能会降低光电探测器在低光水平下的性能，降低其灵敏度。在这里，我们表明，对于大多数具有内部增益的低维光电探测器，灵敏度取决于结电容。由于极低的结电容和减少的电荷屏蔽，低维材料和器件在追求高灵敏度光电探测器方面比体半导体具有明显的优势。本综述描述并验证了一种从外部光响应测量中估算电容的方法，提供了一种直接的方法来提取器件的灵敏度，并与物理极限进行基准测试。这种改进的物理理解可以指导低维光电探测器的设计，有效地利用其独特的优势，并实现超过现有最佳光电探测器的灵敏度。
