Dependency of depletion capacitance on switching threshold of an inverter

Abstract

Depletion capacitance of a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is a critical parameter that determines the switching threshold of an inverter. The study of this dependency is lacking in the literature. This challenge is addressed by demonstrating a prerequisite for effectively modulating the Hole Concentration (HC) in the channel towards the bulk region of the Zener Tunnelling Tunnel Diode Partially Depleted Silicon On Insulator (ZT-TDPDSOI). The modulation of HC facilitates a variable capacitance effect, leading to a reduction in the subthreshold swing (SS). Fermi level (FL) and electric field analyses are conducted to investigate the variation in HC and the resultant change in capacitance. Furthermore, the effect of the bulk potential, originating from the variation in HC at the drain-channel junction, is revealed. FL and Valence Band Energy (VBE) are used to explain the concentration variation within the channel near the drain-channel region. Doping of P⁺ region below source/drain modulates the HC in the channel. The HC extracted from energy band diagram is validated through box profile approximation (BPA). ZT-TDPDSOI is implemented in the inverter circuit and verified the increase in the switching threshold and transition slope there by increasing the efficiency of inverter. Transfer characteristics of inverter is analysed here. There is 12% increase in switching threshold, 4% increase in transition slope and 8% reduction in risetime in ZT-TDPDSOI. All simulations are performed using atlas and mixed signal Technology Computer Aided Design (TCAD).