Direct Observation of Interface Charge Behaviors in FeFET by Quasi-Static Split C-V and Hall Techniques: Revealing FeFET Operation

A quasi-static split C-V technique is proposed as a novel method to monitor ferroelectric polarization and charge distribution in FeFETs. In contrast to conventional split C-V, which is not applicable to FeFETs, the proposed technique successfully detects charges induced by V
_g
at the ferroelectric-semiconductor interfaces and extracts real P-V
_g
and Q-V
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characteristics of FeFETs. Through a combination with Hall measurements, responses of minority/majority carriers and trapped charges associated with polarization switching in FeFETs are experimentally obtained for the first time. It is found that trapped carriers, which screen ferroelectric polarization, is a key factor in the device operation of MFIS-FeFET. Our method, extracting Q-V
_g
loops directly from FeFET structures, is a powerful tool to understand the real operation and device physics of FeFETs including the memory window and the NC effect.