Photodetectors are key optoelectronic building blocks performing the essential optical-to-electrical signal conversion, and unlike solar cells, operate at a specific wavelength and at high signal or sensory speeds. Towards achieving high detector performance, device physics, however, places a fundamental limit of the achievable detector sensitivity, such as responsivity and gain, when simultaneously aimed to increasing the detector’s temporal response (speed) known as the gain-bandwidth product (GBP). While detector’s GBP has been increasing in recent years, the average GBP is still relatively modest (∼106-109 Hz-A/W). Here we discuss photoconductor-based detector performance limits and opportunities based on arguments from scaling length theory relating photocarrier channel length, mobility, electrical resistance with optical waveguide mode constrains. We show that short-channel detectors are synergistic with slot-waveguide approaches, and when combined, offer a high-degree of detector design synergy especially for the class of nanometer-thin materials. Indeed, we find that two-dimensional material-based detectors are neither limited by their low mobility nor by associated carrier velocity saturation limitations and can, in principle, allow for 100 GHz fast response rates, which is unlike traditional detector designs that are based on wide channel lengths. However, the contact resistance is still a challenge for such thin photo absorbing materials – a research topic that is still not addressed yet. An interim solution is to utilize heterojunction approaches for functionality separation. Nonetheless, atomistic and nanometer-thin materials used in such next-generation scaling length theory based detectors also demand high material quality and monolithic integration strategies into photonic circuits including foundry-near processes. As it stands, this letter aims to guide the community if achieving the next generation photodetectors aiming for a performance target of GBP ∼ 1012 Hz-A/W.

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增益带宽积增强型光电探测器路线图

光电探测器是执行基本光电信号转换的关键光电构建块，与太阳能电池不同，光电探测器以特定波长和高信号或传感速度运行。然而，为了实现高探测器性能，器件物理学对可实现的探测器灵敏度（例如响应度和增益）设置了基本限制，同时旨在提高探测器的时间响应（速度），即增益带宽积 (GBP)。虽然近年来探测器的 GBP 一直在增加，但平均 GBP 仍然相对适中（~106-109 Hz-A/W）。在这里，我们根据与光载流子通道长度、迁移率、具有光波导模式约束的电阻。我们表明，短通道探测器与缝隙波导方法具有协同作用，并且当结合使用时，可提供高度的探测器设计协同作用，尤其是对于纳米薄材料类。事实上，我们发现基于二维材料的探测器既不受其低迁移率的限制，也不受相关载流子速度饱和的限制，原则上可以实现 100 GHz 的快速响应速率，这与基于宽通道长度。然而，接触电阻对于如此薄的光吸收材料来说仍然是一个挑战——一个尚未解决的研究课题。临时解决方案是利用异质结方法进行功能分离。尽管如此，在这种基于下一代缩放长度理论的探测器中使用的原子级和纳米级薄材料也需要高材料质量和单片集成策略到光子电路中，包括近代工厂工艺。就目前而言，这封信旨在指导社区是否实现旨在实现 GBP ∼ 1012 Hz-A/W 性能目标的下一代光电探测器。