Quantum transport simulation study of negative capacitance FETs based on the Landau theory and its applications

Abstract

Negative capacitance FETs (NCFETs) are suggested as one of the candidates to overcome the fundamental thermal limit of conventional MOSFETs. In this work, we investigate the basic characteristics of short-channel NCFETs with quantum mechanical transport coupled with Landau-Khalatnikov (LK) equation for modeling the ferroelectric gate stack. In the conventional transistor, potential barrier is lowered with increasing drain voltage, which is a typical drain-induced barrier lowering but in the NCFETs, the potential barrier is raised with drain bias, which we call the drain-induced barrier rising (DIBR). DIBR causes negative differential resistance in output characteristics of NCFETs. DIBR also induces the hysteresis behavior in voltage transfer characteristics (VTC) of NCFET inverters, even though the hysteresis behavior does not appear in the transfer curve of the NCFETs. However, the hysteresis of the NCFET inverter is a key to a new application. Schmitt trigger inverters which filter the noise in circuits consist of 4 to 6 MOSFETs, while the NCFET based Schmitt trigger is composed of two devices, n type and p type. It suggests a possibility of expansion of the applications.