Fabrication And Properties Of Graphene Fieled-effect Transistors

The first experimental discovery of monolayer graphene by Professor Geim in Manchester is a seminal event in physics science in 2004.With the development of studies,many superior physical and chemical properties of graphene were found out,especially its fascinating electrical properties.Graphene field effect transistor(GFET)has extraordinarily high response frequency and ultra small size,which expected to be the basic device of semiconductor in the future.This dissertation focuses on the fabrication and the related performance of the GFETs.Monolayer and bilayer epitaxial graphene on Si face SiC substrates is prepared in this thesis.The material properties of epitaxial graphene are characterized,including the crystal quality,surface topography and electrical properties.An improved device process is used to fabricate the ohmic contact electrode,and the contact resistance is found to be as low as 0.088 ?·mm.The properties of contact resistance with monolayer and bilayer graphene are measured.The influence mechanism from carrier density,transmission probability and work function are studied.The formation mechanism of the low Au-graphene ohmic contact is studied.A clean self-aligned fabrication process is used to fabricate the monolayer and bilayer GFET,which achieve a tiny space between source-drain electrodes.The device direct current properties are tested.The RF characteristics are obtained by the S parameters test.Small signal equivalent circuit of the GFET is built.The effect mechanism of electrical parameter on device RF characteristics is studied.The device performance is studied comparatively between monolayer and bilayer GFETs.The device DC performance is studied with the temperature ranging from 25 °C to200 °C in bilayer GFET.Different kinds of scattering under high temperature are taken into count to analyze the device DC performance.The relationship between the temperature and carrier mobility/drifting velocity is studied.Hysteresis effect is investigated.The bilayer GFET is used as the core component to fabricate the graphene amplifier circuit,in which the micro-strip matching technique is used.The amplifier shows a small signal power gain of 3.4 dB at 14.3 GHz.