Analytical model for DC characteristics of optically controlled Gallium nitride MESFET in dark and illuminated conditions

An analytical model has been developed to study the DC characteristics for an optically controlled Gallium Nitride Metal Semiconductor Field Effect Transistor (MESFET). The electrical parameters such as threshold voltage, drain-source current, transconductance and specific on resistance have been determined for dark and illuminated conditions. The Photovoltaic effect due to photo generated carriers under illumination has been studied to modulate the channel cross-section, which in turn changes the threshold voltage, drain-source current and switching speed. The threshold voltage gets reduced under optical illumination condition, which leads the device to operate in depletion mode depending on photon impurity flux density. The resulting I-V characteristics show that the drain-source current is significantly increased with optical illumination compared to the dark condition. Thus it can be seen that because of its superior performance this device can be widely used for optical, power and microwave applications.