NSF-BSF: New Approaches to Contacts to 2D Semiconductors

NEW APPROACHES FOR ELECTRICAL CONTACTS TO SEMICONDUCTING TRANSITION METAL DICHALCOGENIDES New semiconductors such as two-dimensional transition metal dichalcogenides have great potential to advance energy-efficient electronics and satisfy future high computational workloads. However, the electrical resistance for current to flow through transistors fabricated from these semiconductors still limits the performance of devices and circuits. Therefore, researchers at The Pennsylvania State University, in collaboration with counterparts at Technion–Israel Institute of Technology, will exploit complementary expertise to gain fundamental insight into electrical contacts to two-dimensional semiconductors. The insights they gain from testing hypotheses about the origins of contact resistance will allow them to engineer contacts with ultra-low resistance. This project will train graduate and undergraduate students by involving them in research relevant to industry and leading laboratories around the world. The principal investigators will engage in exchange visits for intensive planning and outreach activities to student groups, including outreach to undergraduate honors students at The Pennsylvania State University and middle school girls. Through their own exchange visits, students will gain hands-on experience in complementary research techniques and a global perspective on research. The project will have scientific and technological impact in the fields of semiconductor devices and two-dimensional materials. Considering the advantages and diverse functionality afforded by two-dimensional semiconductors, they have the potential for enormous economic impact through integration with existing, ubiquitous silicon technology. Other technologies that may be impacted include transparent displays and flexible electronics.Two-dimensional semiconductors based on transition metal dichalcogenides are ideally suited for short-channel transistors and energy-efficient logic devices that can be integrated in a monolithic three-dimensional fashion or used for flexible electronics. Yet one of the key challenges to advancing this technology is contacting the semiconductors with low resistance. Moreover, the metal/semiconductor interface plays a crucial role in determining the carrier type in the channel of the transistor. Researchers at The Pennsylvania State University and Technion–Israel Institute of Technology will test hypotheses on the role of metal deposition, use of semimetals, and junction formation on the resistance of contacts to atomically thin semiconductors. They will perform experiments to separate the confounding effects of key variables to gain deeper insight into the metal/semiconductor interface. Their work to elucidate the physics of contacts will be aided by materials discovery of new semimetals. The Pennsylvania State University will exploit decades of experience studying interfacial reactions at contact interfaces, materials characterization, and thin-film synthesis. At the Technion, research will build upon recent insights on current transport in two-dimensional semiconductor devices, including the design of specialized test structures to pinpoint the origin of the components of resistance. By combining these strengths, the team will develop a deeper understanding of Fermi-level pinning in contacts to two-dimensional semiconductors and how to engineer contacts with unprecedented low contact resistances.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.