The objective of this program is to demonstrate new nanoscale photodetectors with high sensitivity and bandwidth for nanophotonic integrated circuits. The approach exploits self-assembly or solution-process of nanocrystal quantum dots in nanogap electrodes to achieve high fabrication integratability with varieties of nanophotonic components. Incorporation of plasmonic effects and new fabrication processes to reduce tunneling barriers are explored to enhance sensitivity and bandwidth. Intellectual merit: This research will demonstrate new design and fabrication of nanoscale quantum dot photodetectors that can be readily incorporated into nanophotonic device integration. The device structure utilizes concentrated high electric field for enhanced efficiency and charge transport. The research on optimizing chemistry and conditions for quantum dot deposition will offer a route to increased speed, a major challenge for quantum dot devices. The utility of plasmonics to concentrate optical field and enhance quantum efficiency will help addressing the prevailing question of optical coupling in nanophotonics. If successful, the research will provide a first solution to fully integratable nanophotonic photodetection. Broader impact: The growing field of Nanophotonics has increased the demand for faster, smaller, and more sensitive on-chip photodetection. Given the divergence in materials and fabrication processes in nanophotonics, a nanoscale photodetector with full fabrication integratability has yet to be demonstrated. Success of this research could have a transformative impact in nanophotonic integrated circuits and broader fields of optical computing, communications and sensing. This research will also provide exciting multidisciplinary training opportunities for graduate and undergraduate students, and lead to broader impact to the society through diversity development, education and outreach activities.
Over the last several decades QDs have been an area of intense research due to their unique optical and electrical properties that arise from the very small size of the particles resulting in a quantification of energy levels of the particle. Research proof of concept devices have suggested that QDs hold unique optical properties that are far superior to the corresponding materials in bulk form, such as high quantum efficiency, size-dependant tunable absorption, and high sensitivity. These make them ideal for the use in optical sensors, although developing a scalable manufacturing process has been challenging. If a CMOS compatible manufacturing process can be developed QD-based photodetectors would find immediate use for a wide range of applications due to their small size, low cost, flexibility, high sensitivity and high performance. Our research focuses on solving this problem by developing a design and process enabling QDs to be deposited by solution process between contact electrodes with sub-micron spatial detection resolution. The fabrication process can be done on a wide variety of substrates; therefore this process is compatible with current CMOS technologies and will allow QDs of any material, including compound semiconductors not compatible with silicon CMOS processes, to be used allowing photodetectors to be created for a wide range of regions of the spectra for a myriad of applications, such as high-resolution imaging arrays and high-sensitivity devices for low light levels including biomedical devices, military and scientific applications. Additionally this technology is compatible with emerging non-silicon based processes, such as polymer based electronics, leading to a new generation of low cost but capable optical sensing devices. We have also fabricated QDs using non-toxic materials such as Si, which can further broaden the application scope of the technology.
