Asymmetric Polarization Response of Electrons and Holes in Si FeFETs: Demonstration of Absolute Polarization Hysteresis Loop and Inversion Hole Density over 2×1013 cm−2
Kasidit Toprasertpong, Zhijian Lin, T. E. Lee, Mitsuru Takenaka, Shinichi Takagi
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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> enhanced up to 2.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . 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.