A New Analytical Model for Improving Sub-threshold Conduction of MOSFETs

In this paper, an analytical model representing a long channel MOSFET structure with larger effective channel thickness is proposed which reduces sub-threshold current to pico ampere level. The effective depletion channel thickness is calculated and utilized to find a mathematical expression for sub-threshold current. At first, the equation of a tangent is drawn at surface potential of potential vs. depletion depth curve. The equation of the tangent is derived from solving 1-D Poisson’s equation at SiO2-Si interface. The intersection of tangent with the horizontal axis is assumed as the new effective channel thickness of sub-threshold conduction channel. Further inclusion of gate voltage shifts due to interfacial traps, mobile ions and fixed ions modifies the derived equation and increases the magnitude of sub-threshold current to nano ampere range. This proposed model substantially lowers sub-threshold current in MOSFET than previous models predicted