Yang Kewu

Improvement of Metal-Graphene Ohmic Contact Resistance in Bilayer Epitaxial Graphene Devices*

We report on an improved metal-graphene ohmic contact in bilayer epitaxial graphene on a SiC substrate with contact resistance below 0.1 ωmm. Monolayer and bilayer epitaxial graphenes are prepared on a 4H-SiC substrate in this work. Their contact resistances are measured by a transfer length method. An improved photoresist-free device fabrication method is used and is compared with the conventional device fabrication method. Compared with the monolayer graphene, the contact resistance Rc of bilayer graphene improves from an average of 0.24 ωmm to 0.1 ωmm. Ohmic contact formation mechanism analysis by Landauers approach reveals that the obtained low ohmic contact resistance in bilayer epitaxial graphene is due to their high carrier density, high carrier transmission probability, and p-type doping introduced by contact metal Au.

Fibre Optical Parametric Amplification in Defect Bragg Fibres with Zero Dispersion Slow Light Effect

Nonlinearity enhancement by slow light effect and strong light confinement in defect Bragg fibres is demonstrated and analysed in applications of fibre optical parametric amplifiers. Broadband low group velocity and zero dispersion as well as the strong light confinement by band gap enhances the nonlinear coefficient up to more than one order than the conventional high nonlinear fibres. Moreover, the zero dispersion wavelength of coupled core mode can be designed arbitrarily, under which the phase-matching bandwidth of the nonlinear process can be extended.