A self-consistent pseudo-two-dimensional model for hot-electron current in MOST' s

A theoretical formulation for the hot-electron currents (substrate and gate currents) in MOST's with nonuniform impurity profile has been built. By applying a gradual channel approximation for the source section and a pseudo-two-dimensional approximation for the drain section, saturation voltage is obtained by considering the voltage and channel current continuity at the boundary of the two sections. Three fitting parameters in the model are determined by comparing the theoretical calculation results with the observed substrate current in samples with various device parameters. The present model was successfully applied to describe the two experimental results: the gate oxide thickness dependence of the gate current injection efficiency and the kink in the maximum channel electric field strength versus gate voltage (= drain voltage) relation. The nonuniform channel impurity profile is approximated by the modified Gaussian distribution, which is found to agree well with the estimation by the substrate bias effect of MOST's. The calculated gate currents for the device can well explain the implantation energy dependence of the measured gate currents.