Mathematical modelling of accumulation layer thickness of fully depleted G4-FETs

A physics based mathematical model is proposed here to determine the accumulation layer thickness in thin film fully depleted G⁴-FETs. The model was derived as a function of surface potential which was calculated by self-consistently solving two dimensional Poisson´s equation. The dependence of accumulation layer thickness on gate biases as well as the device structural parameters are also analysed here. The purpose of proposing this model is to determine the range of structural parameters for designing the devices, within which the accumulation layer thickness remains small enough to be approximated as a sheet of charge of zero thickness so that popular charge sheet model can be used to analyse transistor characteristics. Moreover, the biasing range can be determined also for which charge-sheet model can be used to design circuits.