I-v Characteristics and Transconductance Modeling for Dual Channel Algan/Gan Modfets

Abstract

In this paper we present 2-D analytical model for I-V characteristics and transconductance of dual channel AlGaN/GaN Modulation Doped Field Effect Transistor (DC-MODFET) to demonstrate the current-voltage as well as transfer characteristics of the device structure under different bias conditions. The model analyses sheet charge density and finaly current density in each of the top and bottom channels using effective device threshold expressions based on spontaneous and piezoelectric polarization dependent two dimensional electron gas (2-DEG). An aluminum mole fraction graded doping profile in bottom barrier layer has been used for bottom channel sheet carrier density. Trapping/detrapping surface states are also considered to determine device drive current and trans-conductance expressions. The presence of double channels in the device minimize the current collapse problems, is accurately explained in our proposed model. The current collapse that occurs more in the top channel nearer to the gate, is subsidized by the current in bottom channel, hence minimizing overall current collapse in the device. Finally, the numerical predictions from our model are compared with the published experimental results and found to be in close agreement.