Top-Gate Stack Engineering Featuring a High-κ Gadolinium Aluminate Interfacial Layer for Field-Effect Transistors Based on Two-Dimensional Transition-Metal Dichalcogenides

Abstract

Atomic layer deposition (ALD) of gate dielectrics on two-dimensional transition-metal dichalcogenides (2D TMDs) is challenging due to their chemically inert surfaces. Although various surface pretreatments can form nucleation sites to facilitate the precursor adsorption, preserving 2D TMDs during the pretreatments and maintaining gate stack quality with the weak 2D TMD/dielectric interface become the main concerns. In this work, we combine physisorbed-precursor-assisted (PPA)-ALD to minimize damage to 2D TMDs with a second interfacial layer for performance enhancement. Ultrathin GdAlO3 interlayers are integrated into 2D TMD gate stacks with PPA-ALD AlOx seeding layers and HfO2 top dielectrics. Further, 1-nm-thick and pinhole-free GdAlO3 can be deposited on AlOx-seeded monolayer (1L) WS2 by ALD at 250 °C. The material properties of 1L WS2 are preserved, as confirmed by Raman spectroscopy. After the GdAlO3 layer insertion, 1L MoS2 dual-gate (DG) field-effect transistors (FETs) show improved subthreshold swing (SS), field-effect mobility, and Id–Vg hysteresis without compromising the capacitance-equivalent thickness (CET). The proposed strategy is wafer-scale compatible and extendable to the future nanosheet gate-all-around structures.