A Unified Depletion/Inversion Model for Heterojunction Trigate FinFETs DC Characteristics

Abstract

This paper presents a comprehensive I-V model for the evaluation of above threshold DC characteristics of trigate AlGaN/GaN FinFETs for both depletion and inversion mode of operations. For the depletion mode, 2DEG carrier concentration, n_{s} , is evaluated considering the trigate geometry of the device, which is then used to assess drain current (I_{\text {2D}}) for both the linear as well as the saturation region of operations. At a relatively higher gate bias, where the 2DEG is fully un-depleted, a significant rise in the drain current is observed which is associated with the creation of two additional side channels in the GaN layer of AlGaN/GaN FinFET, caused by the inversion of carriers. This component of the drain current, referred to as inversion current ( I_{inv} ), is modeled using the solution of a 2D Poisson equation. The total current ( I_{ds} ) is the summation of both the depletion as well as the inversion currents ( I_{ds} = I_{inv} + I_{\text {2D}} ). The developed technique is validated using experimental data and is seen to exhibit a good degree of accuracy. Therefore, the proposed model could serve as a useful tool to predict AlGaN/GaN FinFETs output and transfer characteristics.