Unraveling In‐Plane Crystallographic Anisotropy‐Dependent Memory Performance In Van Der Waals α‐In ₂ Se ₃ Ferroelectric Semiconductor Field‐Effect Transistors

Abstract The ferroelectric semiconductor field‐effect transistors (FeS‐FETs) based on α‐In 2 Se 3 emerge as promising non‐volatile memory devices. However, the intrinsic in‐plane (IP) crystallographic anisotropy of α‐In 2 Se 3 introduces orientation dependence, leading to pronounced variations in memory performance depending on the IP alignment of the source/drain (S/D) contacts. This study presents the first demonstration of IP anisotropy‐dependent ferroelectricity in α‐In 2 Se 3 FeS‐FETs with S/D contacts aligned along the armchair (AC) and zigzag (ZZ) directions. The AC‐aligned S/D configuration achieves a ferroelectric resistance switching (FRS) ratio of 6.42, an on/off current ratio of 4.53 × 10 4 , and a normalized memory window (MW) of 59 %, whereas the ZZ‐aligned counterpart exhibits an FRS ratio of 1.05, an on/off ratio of 5.25, and negligible MW. The electron transports proceed through twisted pathways along the AC direction, but proceed along a straight trajectory in the ZZ direction to avoid high‐energy barrier regions due to the threefold rotational symmetric lattice. Thus, the excessive electron transmission and a reduced Schottky barrier height effectively screen the influence of ferroelectric bound charges in the ZZ‐aligned S/D contacts. These findings establish clear correlations between IP anisotropy and the ferroelectric functionality of α‐In 2 Se 3 , offering critical guidelines for the design of FeS‐FETs.