Optical sensing in the mid- and long-wave infrared (MWIR, LWIR) is of paramount importance for a large spectrum of applications including environmental monitoring, gas sensing, hazard detection, food and product manufacturing inspection, and so forth. Yet, such applications to date are served by costly and complex epitaxially grown HgCdTe quantum-well and quantum-dot infrared photodetectors. The possibility of exploiting low-energy intraband transitions make colloidal quantum dots (CQD) an attractive low-cost alternative to expensive low bandgap materials for infrared applications. Unfortunately, fabrication of quantum dots exhibiting intraband absorption is technologically constrained by the requirement of controlled heavy doping, which has limited, so far, MWIR and LWIR CQD detectors to mercury-based materials. Here, we demonstrate intraband absorption and photodetection in heavily doped PbS colloidal quantum dots in the 5-9 μm range, beyond the PbS bulk band gap, with responsivities on the order of 10-4 A/W at 80 K. We have further developed a model based on quantum transport equations to understand the impact of electron population of the conduction band in the performance of intraband photodetectors and offer guidelines toward further performance improvement.

中文翻译：

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通过PbS胶体量子点中的带内跃迁实现中波和长波红外光电。

中波和长波红外（MWIR，LWIR）中的光学传感对于包括环境监测，气体传感，危害检测，食品和产品制造检查等在内的众多应用来说至关重要。然而，迄今为止，这种应用是由昂贵且复杂的外延生长的HgCdTe量子阱和量子点红外光电探测器实现的。利用低能带内跃迁的可能性使胶体量子点（CQD）成为用于红外应用的昂贵低带隙材料的诱人低成本替代品。不幸的是，表现出带内吸收的量子点的制造在技术上受到受控重掺杂的要求的限制，迄今为止，重掺杂的要求已将MWIR和LWIR CQD检测器限于汞基材料。这里，