Hf_0.4Zr_0.6O₂ Thickness-Dependent Transfer Characteristics of In_xZn_1-xO_y Channel Ferroelectric FETs

We investigate how the threshold voltage (V_T) is adjusted to create a memory window (MW) in ferroelectric field-effect transistors (FeFETs) composed of ferroelectric Hf_0.4Zr_0.6O₂ and InZnO (In₂O₃:ZnO = 9:1 wt %). Temperature-dependent polarization measurements reveal a dipole switching in Hf_0.4Zr_0.6O₂. The properties of the n-type InZnO channel are examined by fabricating an oxide transistor with an HfO₂ gate dielectric. Upon replacement of HfO₂ with Hf_0.4Zr_0.6O₂ in the oxide transistor, a counterclockwise MW is observed. Specifically, as the Hf_0.4Zr_0.6O₂ thickness increases from 16 to 24 nm, the V_T of the FeFET after a + gate voltage (V_G) sweep remains nearly constant, while the V_T after a −V_G sweep shifts significantly from −0.9 to 0.5 V. The enlarged MW of approximately 2 V, which is proportional to the Hf_0.4Zr_0.6O₂ thickness in the FeFET, can be explained by considering the balance between V_G controllability across the gate stack and the ferroelectric switching of Hf_0.4Zr_0.6O₂