  In this work, we propose an explicit analytical equation to show the
variation of top gate threshold voltage with respect to the JFET bottom gate
voltage for a Flexible Threshold Voltage Field Effect Transistor (Flexible-FET)
by solving 2-D Poisson's equation with appropriate boundary conditions,
incorporating Young's parabolic approximation. The proposed model illustrates
excellent match with the experimental results for both n-channel and p-channel
180nm Flexible-FETs. Threshold voltage variation with several important device
parameters (oxide and silicon channel thickness, doping concentration) is
observed which yields qualitative matching with results obtained from SILVACO
simulations.
