Optimized MFS Stack With N-Doped TiO2 Channel and La-Doped HfO2 Ferroelectric Layer for Highly Stable FeFETs

In this study, an optimized metal-ferroelectric –semiconductor (MFS) stack containing a La-doped HfO2(HLO) ferroelectric (FE) layer and an N-doped TiO2 (NTO) channel is proposed and used to fabricate highly stable ferroelectric field-effect transistors (FeFETs). HLO and NTO were continuously deposited via atomic layer deposition without breaking the vacuum. Uniform and crystallized FE layers and channels are confirmed in the optimized MFS stack. The fabricated FeFETs exhibit excellent electrical and thermal stability, including a 1.82-V memory window (MW) and high endurance over $10^{{8}}$ cycles with a wide process window above 700°C during rapid thermal annealing. Moreover, ambient stability of oxide semiconductor channel-based FeFETs with 115-mV MW shift after one year of air exposure without a passivation layer was demonstrated for the first time.