Improved Negative-Capacitance Switch of Ferroelectric Field Effect Transistor Using Defect Passivation Engineering

A ferroelectric negative-capacitance (NC) transistor using aluminum-doped hafnium oxide (HfAlO_x) with fluorine passivation is successfully demonstrated. The fluorine-passivated device shows a nearly hysteresis-free forward/reverse swing of sub-30 mV dec⁻¹ for symmetric switch, a wide sub-60 mV (dec·swing)⁻¹ range over 4 decades of drain current, an ultralow off-leakage current of 4 fA μm⁻¹, and a high on/off current ratio of >10⁸. The fluorine defect passivation (FP) reduces oxygen vacancies of ferroelectric HfAlO_x to mitigate interface depolarization field and thereby reinforce surface potential amplification effect during NC operation.