NSF Award
2423217
This IMPRESS-U project is jointly funded by NSF, Latvian Council of Science (LCS), US National Academy of Sciences, and Office of Naval Research Global (DoD). The research will be performed in a multilateral international partnership that unites the University of Arkansas (US), Riga Technical University (Latvia), and Taras Shevchenko National University of Kyiv (Ukraine). US portion of the collaborative effort will be co-funded by NSF OISE/OD, EPSCoR/OD, and MPS/DMR/EPM programs.<br/><br/>PART 1 - Progress in science, economy, national defense; fundamental issues, project advances the field, supports education and diversity, or benefits society.<br/>U.S. dominance of Night Vision technology, once considered “the single greatest mismatch of the Gulf War”, is now in question. In the face of stepped-up international investment, U.S. innovation in night vision technology has largely remained unchanged and the U.S. advantage has been shrinking. This award supports research led by the University of Arkansas to help address this gap through discovery and development of a new and novel family of semiconductors, alloys of SiGeSn, that can potentially beat all current IR technology on both cost and performance. The outcome will have a significant impact on the military ability to see better at night and allow storing and sharing of images wirelessly with other warfighters at a different location, ship, or aircraft. Providing such tactical advantages of night operations to the soldier, aircraft, missiles, drones, robotics of any type, is a key factor in determining the outcome in conflict and perhaps even preventing conflict. The issue, however, is that efforts to realize this potential, have been significantly challenged by the difficulty of fabricating (Si)GeSn with sufficiently high Sn concentrations and crystal quality that are needed for creating a direct bandgap semiconductor with high performance. Currently no one has been able to demonstrate SiGeSn with high Sn content and high-quality material. In partnership with Ukrainian and Latvian scientists, the goal of this research is to demonstrate two new and novel “Synthesis Methods” for the fabrication of (Si)GeSn thin film semiconductor alloys that manipulate the position of Sn atoms within the thin film to achieve (Si)GeSn with low misfit dislocations and high Sn content for the first time.<br/>Achieving this goal will have an impact beyond national defense since the country that leads in advanced semiconductor IR imaging technology will also lead in the race to market nearly all new game-changing military and civilian IR imaging technologies, from ground to space warfare to cell phones to medical imaging. It also enhances US competitiveness in new and exciting industries from self-driving vehicles to robotics to surveillance to medical imaging. From this perspective, the SiGeSn semiconductors semiconductor is the ideal new material to advance night vision imaging due to greater capability to engineer the bandgap, longer carrier lifetime, larger absorption coefficient, and lower dark current, all adding up to higher sensitivity. An additional advantage is that SiGeSn is compatible with current Si technology resulting in lower production cost compared to current IR imaging systems. These factors emphasize that the advantage of SiGeSn is that it can potentially beat all current technology on performance and cost, - an advantage for each soldier on the battlefield and each American in everyday life. <br/><br/>PART 2 - Goals and scope, methods and approaches and potential contribution. <br/>The objective of this proposal is to overcome current roadblocks to developing high quality, thin film, stable (Si)GeSn alloys on Si for lighter, faster, higher signal-to-noise, and more energy efficient 2-5 µm infrared devices as the next generation of infrared technology. While (Si)GeSn is an exciting new semiconductor possibility, efforts to realize its potential through traditional growth methods by molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) are challenged by the difficulty of fabricating (Si)GeSn with both the needed Sn concentration and high crystal quality. The issue is that a Sn content greater than 6% Sn is necessary for an indirect-to-direct bandgap transition, which is critical for high optical emission, and a Sn content of ~ 20% Sn is needed to span the near and mid infrared (IR) spectral range. However, at Sn concentrations greater than ~ 10% Sn, due to a significant lattice mismatch between SiGeSn and Si and the low miscibility of Sn in Si (1%), the material develops a high density of misfit and threading dislocations defects, followed by Sn segregation, resulting in high optical losses limiting optical applications. Currently, no one can deliver high Sn content and high material quality, limiting application.<br/>In contrast to these more traditional growth approaches, this project integrates the unique expertise and capability of US, Ukrainian, and Latvian scientists to explore a totally new route to extend the Sn content while maintaining high-quality. The proposed methods rely on the epitaxial growth of fully strained high-quality (Si)GeSn with Sn content of about 10% Sn. This is followed by applying two novel methods to redistribute Sn within the thin film to increase the Sn content from 10% to ~20% locally without misfit and threading dislocations and Sn segregation. <br/>The research partnership to fabricate high-Sn high-quality (Si)GeSn directly on Si substrates makes “monolithic integration” and large-scale manufacturing possible, and at lower cost. The impact reaches well beyond the obvious military applications, impacting high-speed photonics, medical care, surveillance, search/rescue, self-driving vehicles, meteorology, and climatology, each today experiencing an increasing reliance on IR detector technology. Beyond technology, the project will impact developing an engaged semiconductor workforce and strengthen the research, education, and innovation ecosystem. Education will focus on training students who will be experts in semiconductors, the design of novel devices, fabrication principles, and the equipment used to manufacture those devices. Moreover, SiGeSn is a cutting-edge enabling technology that can both give birth to new industries and dramatically transform existing ones, creating opportunities for economic growth and job creation.<br/><br/>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.
