MSE Seminar: Dr. Tingyi Gu, University of Delaware, Electrical and Computer Engineering
Wednesday, March 15, 2023
3:30 a.m.-5:00 a.m.
Room 2110 CHE
301 405 1935
Title: Integrated photonic interface of van der Waals materials and low power optoelectronics
Inspired by the condensed material physics research society, van der Waals (vdWs) semiconductor materials fascinate nanoscale device engineers with their unique optoelectronic properties that can fundamentally address the circuit or system level limitations on speed and power consumptions. In this
talk, I will focus on two heterogeneous structures for vdW material on silicon photonics: (1) polymorphic layered material based integrated photonic memory and (2) few micrometers graphene homojunction by back gate silicon p-i-n junction, followed by the correspondent integrated meta-photonic architectures
which can leverage the materials potentials for future optical computing and communications.
The chalcogenide optical phase change materials build on amorphous-crystalline phase transitions, where the high melting temperature and slow cooling required for crystallization set their power and reset time
limitation. The nonvolatile phase transitions pathways between the two topologically similar layered indium selenides (In 2Se3 ) can potentially break the material limitation, through transitions between two topologically similar layered crystalline states (α and β). which have the same underlying rhombohedral crystal system. The 0.81eV fundamental bandgap difference between the two states promises sufficient contrast of their refractive index and conductivity. Experimental implementations on hybrid silicon microring resonators demonstrated the feasibilities of all-optical and electro-optic memory based on the new phase transition mechanism and revealing the material and structural transitions in high precision. The low energy and nanosecond reset time promise the layered In 2 Se 3 an emerging candidate for future
optical in-memory computing.
Graphene has the highest carrier mobility among the vdW materials, and the carrier transient time along the channel is minimized with ballistic transport condition. However, the formation of large build-in electric field area is always a challenge. Leveraging the scalable and atomically flat silicon photonic
platform, graphene can be seamlessly in direct contact with the foundry manufactured lateral silicon homojunctions, with substrate defined junction area. Graphene significantly improves the device speed through ultrafast out-of-plane interfacial carrier transfer and the following in-plane built-in electric field
assisted carrier collection. More than 50 dB converted signal-to-noise ratio at 40 GHz has been demonstrated under zero bias voltage, the quantum efficiency could be further amplified by hot carrier gain on graphene-i Si interface and avalanche process on graphene-doped Si interface.
Bio: Tingyi Gu’s research focuses on integrated photonic devices, developing optical components with new materials for optical communication and sensing applications. Her work studies nanophotonic and electronic properties of nanostructured materials built by different integration techniques and aims to
achieve a good understanding of how to guide the nanostructured materials towards a scalable integrated photonic system. She joined the ECE faculty of the University of Delaware in the fall of 2016. She received M.S. and Ph.D. degrees in electrical engineering from Columbia University. She completed her
postdoctoral training at Princeton University as a PRISM fellow, studying solution processed chalcogenide materials under guidance of Prof. Craig B. Arnold. She received young investigator awards from AFOSR, NASA, ARO and DARPA.