Asymmetric Polarization Response of Electrons and Holes in Si FeFETs: Demonstration of Absolute Polarization Hysteresis Loop and Inversion Hole Density over $2\times 10^{13}\mathrm{cm}^{-2}$

Abstract

We have investigated the device operation of Si ferroelectric FETs (FeFET) through direct measurements of polarization and electron/hole densities in p-FeFETs and n-FeFETs. Unlike electrons in n-FeFETs, inversion holes in p-FeFETs are found to be well coupled with ferroelectric polarization, resulting in inversion hole density $N_{s}$ enhanced up to $2.5\times 10^{13}$ cm−2. Based on experimentally-confirmed ferroelectric-semiconductor coupling behaviors, we propose a method to extract absolute polarization in ferroelectric gate stacks without centering P-V loops. We demonstrate that obtaining accurate polarization states is a key to understand the FeFET characteristics: it explains the physical origin of a difference in the memory window between p- and n-FeFETs.