Analytical modelling of the current (I)-voltage (V) characteristics of sub-micron gate-length ion-implanted GaAs MESFETs under dark and illuminated conditions

An analytical model for current (I)-voltage (V) characteristics of a short-channel ion-implanted GaAs MESFET has been presented for dark and illuminated conditions. For the sake of simplicity, the non-analytic (i.e. non-integral) Gaussian doping function commonly considered for the channel doping of an ion-implanted GaAs metal semiconductor field effect transistor (MESFET) has been replaced by an analytic Gaussian-like doping profile in the vertical direction. The device uses an indium-tin oxide-based Schottky gate through which an optical radiation of 0.87 mu m wavelength is coupled from an external source into the device to modulate the I-V characteristics of the short-gate length GaAs MESFET. The coupled light generates electron-hole pairs in the active channel region below the gate and develops a photovoltage across the Schottky gate-channel junction and modulates the device characteristics. This study also includes the modelling of this photovoltaic effect by taking the short-gate length effects into consideration. The developed model includes the effects of doping profile and device parameters on the drain current of the short-channel ion-implanted GaAs MESFETs under dark and illuminated conditions of operations. The accuracy of the proposed model is extensively verified by comparing the theoretically predicted results with numerical simulation data obtained by using the commercially available ATLAS (TM) device simulation software.