Research On Infrared Detection Performance Of Graphene

Graphene,as an emerging 2D material,has ultra-high electron mobility,unique energy band structure,low density of states and tunable Fermi energy.These unique properties make it attractive for photodetections,especially in the infrared spectral band.In this thesis,the photoresponse of graphene-Au heterojunction was investigated.The grapehene-Au heterojunction photodetectors were designed and fabricated,then their photovoltaic response was characterized with the energy band theory.Then a "metal-dielectric-graphene-antenna" plasma-enhanced absorption structure was designed and simulated by the finite element electromagnetic simulation tool Ansoft HFSS,and the optical absorption characteristics of this structure in the middle infrared band were also studied theoretically and experimentally.The main contents and contributions of this thesis are summarized as below.(1)Using standard energy band theory,the unique band structure of graphene-Au heterojunction is constructed,which suggests a photovoltaic photoresponse mechanism.Based on this photorsponse mechanism,we designed a heterojunction photodetector made of a graphene sheet atop of a finger-shaped Au electrode.(2)A graphene-Au heterojunction photodetector sample is fabricated in experiments.The fabrication process includes the growth and transfer of graphene,the pattering and fabrication of finger-shaped Au electrode.(3)Photovoltaic response of the graphene-Au heterohunction is characterized.The measurements reveal a photovoltage response in the visible to infrared(405 nm-980 nm)spectral region with a cut-off wavelength at about 980 nm,which is likely imposed by the Pauli blocking of interband transition in the contact-doped graphene.The photoresponsivity has been shown to decrease with increasing wavelength,and depend critically on the in-plane space charge regions formed at the graphene-Au interface.(4)Antenna-enhanced optical absorption is demonstrated in a "metal-dielectricgraphene-antenna" resonant structure.Using the HFSS simulations,we designed and fabricated multilayered antenna structure,and observed an enhanced absorption at the resonance of the antenna fundamental mode.This thesis investigated the photovoltage responses of graphene-Au heterojunctions,and revealed relevant physical mechanisms underlying the photovoltageresponse.Meanwhile,an antenna-enhanced absorption was also demonstrated in a resonant plasmonic structure.The obtained results add new insights in understanding the photoresponse properties of graphene,and laid a foundation for further development of high performance graphene photodetectors.