Abstract: Behind nearly all computational electronics is complementary metal oxide semiconductor (CMOS) technology consisting of n-type and p-type silicon transistors. Counter-intuitively, actual metal oxide semiconductors still cannot be used for CMOS because their disordered oxide (anionic) lattice has inherently poor p-type conduction properties. To help achieve more energy-efficient CMOS electronics, we measure the sub-gap density of states (DoS) in emerging p-type and established n-type metal oxide transistors of Cu₂O, SnO, and amorphous InGaZnO_x. With 0.1 to 5 eV tunable lasers, the photoconductive response maps the defect density from the valence to conduction band-edges. The resulting sub-gap DoS further simulates transistor transfer curves from first-physics-principles and helps to identify which defect states are roadblocking beyond-silicon CMOS.

As an alternate pathway to beyond-silicon computing, semiconductor molecular crystals suggest new methods for rapid spin-flip technology desired in quantum information. Efficient charge multiplication in single-crystal molecular semiconductors like pentacene generates correlated triplet-pair states with remarkably long spin-coherence. Using femtosecond-resolved microscopy and applied B= 0-7 T magnetic fields, we induce impulsive spin-conversions between the S= 0, 1, and 2 triplet-pairs spin states. Collectively, our demonstration of robust optical spin- and defect-state manipulations in organic crystals and metal oxides suggests future promise for new quantum information and neuromorphic computing paradigms.

Short Bio: Dr. Matt Graham is an associate professor of physics at Oregon State University, where he runs the Micro-Femto Energetics Lab, which develops new spectroscopy methods that study emerging transistor devices and graphene-based quantum materials. His academic path includes a PhD at UC Berkeley and a Kavli Postdoctoral Fellowship at Cornell University, and he presently Chairs the Ultrafast Optical Phenomena Technical Group for Optica (formerly OSA).