Analytical investigation of a triple surrounding gate germanium source metal-oxide-semiconductor field-effect transistor with step graded channel for biosensing applications

This paper proposes a compact analytical model and comprehensively investigates the biosensing performance of a novel dielectric modulated triple surrounding gate germanium source metal-oxide-semiconductor field-effect transistor with a step graded channel. Solving the 2D Poisson's equation yields an analytical expression of threshold voltage, channel potential, drain current and sub threshold swing. The sensitivity variation in the biosensor has been thoroughly studied by varying different device parameters to investigate its biosensing performance. Graded doping in channel offers enhanced sensitivity than a non-graded doped channel when the doping of the channel is more near the drain end than source end which is due to stronger electric field and gate capacitance. Effect of fill-in factor for different biomolecules on the sensitivity has been thoroughly discussed. Different analytical results show an excellent agreement with the simulations done on SILVACO ATLAS TCAD simulator.