Reliability Challenges in Equivalent-Oxide-Thickness Scaling with High-κ Er₂O₃ Dielectrics on Two-Dimensional MoS₂ Field-Effect Transistors

The integration of high-κ films with two-dimensional (2D) semiconductors offers a pathway to advance metal-oxide-semiconductor technology scaling. While reliability studies on gate stacks with 2D semiconductors have focused on device performance instabilities, the stability of bulk dielectric properties, particularly for ultrathin high-κ films on 2D semiconductors, remains underexplored. This work demonstrates the scalability of high-κ Er2O3 on mechanically transferred MoS2, achieving an equivalent oxide thickness below 1 nm. However, the critical issue is identified: time-dependent degradation of the dielectric constant, which persists despite various passivation methods. Notably, this instability is absent when the high-κ film is deposited on a clean surface of MoS2 grown on a sapphire substrate, revealing that the degradation originates from suboptimal surface conditions of the 2D semiconductor rather than the dielectric itself. These findings highlight the necessity of addressing 2D material surface effects to fully realize the potential of ultrathin high-κ dielectrics in future device applications.