Modeling of the Gate Tunneling Current in MFIS NCFETs

Abstract

In this article, we present a model for the gate tunneling current (GTC) in metal-ferroelectric-insulator-semiconductor (MFIS) negative capacitance FETs (NCFETs), which, to the best of our knowledge, is the first such report. The model is numerical in nature, and is developed using the Tsu–Esaki formulation, employing the Wentzel–Kramer–Brillouin (WKB) approximation, in order to estimate the transmission coefficients of the carriers through the barriers. The ferroelectric (FE) material considered is HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and is modeled using the Landau phase transition theory. Simulation results reveal a remarkable nonmonotonic dependence of the GTC on the FE layer thickness, an effect that we explain through the Landau model. Furthermore, it is shown how this GTC can be reduced by orders of magnitude without changing the overall dielectric capacitance—a feature that may prove to be beneficial in low-power circuit designs. Additionally, it is seen that the GTC is a weak function of the remanent polarization and coercive field of the FE. All the model predictions are validated through a comparison with the results obtained from Sentaurus 2-D TCAD simulations. The novel results presented in this work should serve as a guide for detailed experimental studies on the gate current characteristics of MFIS NCFETs.