Analytical Modeling of Surface Potential and Drain Current for Virtually Doped Symmetrical Dielectric Modulated BioFET

Herein we investigate the design considerations for virtually doped, symmetric cavity dielectric modulated BioFET through developed surface potential and drain current analytical models. The models have been deduced using Poisson's equation, considering three sub regions in the channel accounting for formation three effective gate capacitances due to symmetrical structure. The threshold voltage (V
_T
) has been derived from point of minimum potential and constant current method. The presence of different biomolecules in the cavity modulate the threshold voltage (V
_T
) of the device. Shift in threshold voltage (ΔV
_T
) is used as sensitivity metric. The proposed device is effective in detection of weakly charged biomolecules with low dielectric constants (K) such as biotin, streptavadin.The effect of structural design parameters on sensitivity (ΔV
_T
) of the proposed BioFET is studied extensively. Whilst maintaining aspect ratio θ = L
_g\
L
_cavity
equal to 0.4, sensitivity is invariable to gate length (L
_g
) and oxide thickness (t
_ox
) while is significantly affected by channel (t
_Si
) and nanogap (t
_cavity
) thickness. Sensitivity improves with increase in θ and saturates after a certain value. The method of virtual doping of source and drain region relaxes the thermal budget of the fabrication process. The results obtained from developed models have been verified with calibrated simulation results and are found to be in good agreement.