Collaborative Research: Silver-Based Colloidal Quantum Dot Devices for Ubiquitous Mid-Wavelength Infrared Sensing

第1部分：与可见光或近红外夜视相机不同，工作在中波长红外(MWIR)中的光电探测器可以通过雾、雾和其他遮蔽物成像，不需要外部光源，因为它们可以仅通过感知物体发出的辐射来捕捉图像。这些传统上用于军事监视的MWIR光电探测器正在发现越来越多的应用，从夜间驾驶辅助、搜救、生物医学成像到危险化学品的环境监测。然而，现有的MWIR技术昂贵得令人望而却步，不适合这些应用，因为它们需要低温冷却来实现高灵敏度，这使得探测器笨重、耗电。这项拟议的研究旨在实现一种基于新发现的红外胶体量子点(CQD)的颠覆性光电探测器技术，该技术将允许高温操作，从而消除大范围采用的尺寸、重量和功耗障碍。此外，CQD器件的加工与成熟的硅技术高度兼容，这将允许在晶片规模上单片制造光电探测器，从而大幅降低成本。该项目的高度跨学科性质还将为不同水平的学生创造独特的教育机会，有助于增加进入大学科学和工程专业的少数族裔学生，并加强我们在美国的STEM工作队伍。第2部分：本研究的总体目标是全面了解基于硫化物银CQD的光电二极管的器件物理，以展示高温、高灵敏度的MWIR光电二极管。由紧密堆积、强耦合的硫化银量子点组成的薄膜有望通过俄歇抑制实现光电探测器的高温工作。然而，实现高性能CQD光电二极管的主要挑战在于缺乏合适的能带排列的材料组合，以及对光电二极管结构中的器件操作缺乏了解。这项研究虽然是一项进步的器件研究，但将探索一种基于两种类型的CQD形成异质结的新方法，这将使实现高器件性能所需的能级微调成为可能。基于这种方法，该项目将对俄歇抑制和热产生载流子产生的暗电流，以及光电二极管中光产生载流子的输运、复合和捕获产生基本的了解。该项目的成果可能会使一种低成本、高性能的MWIR传感技术在广泛的应用中得到普遍应用。此外，这项MWIR CQD研究，与现有的可见光、近红外和短波红外CQD相结合，将直接促进多光谱成像焦平面阵列的开发。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Part 1:Unlike visible or near-infrared night vision cameras, photodetectors operating in the mid-wavelength infrared (MWIR) can image through fog, mist, and other obscurants and do not require an external source of illumination as they can capture images solely by sensing the radiation that objects emit. These MWIR photodetectors that have been traditionally used for military surveillance are finding growing number of applications ranging from night driving assist, search-and-rescue, biomedical imaging, to environmental monitoring of hazardous chemicals. However, existing MWIR technologies are prohibitively expensive and ill-suited for these applications as they require cryogenic cooling to achieve high sensitivity, making the detector bulky, heavy, and consume large power. The proposed research aims to enable a disruptive photodetector technology based on newly discovered infrared colloidal quantum dots (CQDs) that will allow high temperature operation thereby removing the size, weight, and power consumption barriers to wide-scale adoption. Furthermore, the processing of CQD devices is highly compatible with mature silicon technology that will allow monolithic fabrication of photodetectors at the wafer scale leading to dramatic reduction in cost. The highly interdisciplinary nature of this project will also create unique educational opportunities for various levels of students that will help increase the pool of underrepresented minorities entering science and engineering programs at colleges and strengthen our STEM work force in the US.Part 2:The overall goal of this research is to gain a comprehensive understanding of device physics of photodiodes based on silver chalcogenide CQDs to demonstrate high temperature, high sensitivity MWIR photodiodes. Films composed of close-packed, strongly-coupled silver chalcogenide CQDs have the promising potential to enable high temperature operation of photodetectors through Auger suppression. However, the major challenges in realizing high performance CQD-based photodiodes lies in the unavailability of material combinations with suitable band alignment and the lack of understanding of device operation in photodiode structures. This research, though a progressive device study, will investigate a new method of forming heterojunctions based on two types of CQDs which will enable fine tuning of energy levels needed for achieving high device performance. Based on this approach, this project will generate fundamental understanding of Auger suppression and dark current arising from thermally generated carriers as well as carrier transport, recombination, and trapping of optically generated carriers in photodiodes. The outcomes of this project could potentially enable a low-cost, high performance MWIR sensing technology that will be ubiquitously utilized in a broad range of applications. Moreover, this MWIR CQD research, combined with existing visible, near-, and short-wavelength infrared CQDs, will directly contribute to the development of multispectral imaging focal plane arrays.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.