ABSTRACT: Graphene's optical response is characterized by constant absorption in the visible but electrically-tunable absorption in the NIR-SWIR and plasmonic excitations in the midIR-LWIR spectrum. These traits make for interesting applications in photodetection, light modulation and sensing. To make the response more efficient and competitive, however, the small overall absorption in graphene must be overcome by integrating graphene with resonant photonic or plasmonic cavities. Strong light absorption within the resonators creates hot electrons and temperature gradients. In a comprehensive modeling and design scheme of graphene-based optoelectronic applications, the optical, thermal and electrical responses must be considered within a self-consistent approach: absorption creates hot carriers, whose temperature distribution is determined by the thermal properties of graphene and the appropriate relaxation pathways and corresponding rates. But the thermal properties and the absorption in graphene are themselves functions of the temperature. To successfully solve this, self consistent calculation cycles are employed until convergence. In this work we calculate the field and temperature dependence of all relevant graphene quantities by appropriate integrals of Fermi distribution functions and employ this self-consistent opto-thermo-electric modeling strategy to study a graphene midIR photodetector. In one approach, this is based on a split gated lateral graphene pn junction coupled with a plasmonic bow-tie antenna. The antenna localizes the absorption within a subwavelength spot at the pn-junction while the appropriately designed gating potential shifts the graphene Fermi levels to maximize the temperature gradient and thus the thermoelectric currents generated. We estimate competitive responsivities of the order of 20 mA/W and detectivity above 107 Jones within the 6-10 μm wavelength range. Excellent comparison with recent experiments is found. In another approach, a graphene/Si Schottky junction is utilized, whereby the slow cooling of electrons in graphene allows its sub-bandgap operation in the thermionic regime.
BIOGRAPHY: Dr. Lidorikis is Professor of Computational Materials Science in the Department of Materials Science and Engineering at the University of Ioannina Greece. He received his BSc in Physics from the Aristotle University of Thessaloniki Greece (1993) and his PhD in computational physics from Iowa State University in USA (1999). He held postdoctoral positions in Louisiana State University and Massachusetts Institute of Technology as well as an industry position in the MIT spin-off Luminus Devices Inc. His research interests are in Computational Material Science focusing on nanophotonics and nanoplasmonics, organic- and graphene-based optoelectronics, integrated optics for ICT, multiscale modeling of materials, optical spectroscopy and modeling of nanostructured materials and thin films. He has extensive R&D experience in both academia and industry and co-coordinated several European and National projects (FET, NMP, NMBP, ICT, etc). He is author of over 100 peer-reviewed papers and received over > 5700 citations holding an h-index=33. He is the holder of 19 US patents and given more than 50 invited talks in international conferences.