ALD Reactivity-Driven 2DEG-Like Interfacial Conduction in Nanolaminate InGaZnO Transistors toward High-Mobility and Stable Oxide Electronics

Abstract

Achieving ultrahigh mobility in oxide semiconductors without sacrificing stability has remained a long-standing challenge owing to their inherent disorder and the tradeoff between mobility and stability. In this study, we demonstrated for the first time that the completeness of atomic layer deposition (ALD) surface reactions is the key factor for the formation of well-defined vertical heterostructures in amorphous InGaZnO (IGZO) thin films, which in turn trigger quantum confinement effects and 2Delectron gas (2DEG) like interfacial conduction. By comparing high-reactivity oxygen plasma and low-reactivity ozone as oxidants, we revealed that only plasma-assisted ALD achieved complete surface reactions, yielding atomically ordered InOx–(Ga, Zn)O stacks with distinct interfaces. This engineered structure resulted in an exceptional field-effect mobility (>87 cm2 V−1 s−1) with positive threshold voltage (0.56 V), an apparent two-step conduction signature, and superior stability of the positive/negative bias temperature stability of 0.35/−0.01 V. Temperature-dependent transport from room to cryogenic temperature (83K) and high-temperature annealing (600°C) further confirmed the correlation among reaction completeness, interface quality, and 2DEG-like interfacial conduction. This study identifies a critical link between ALD surface chemistry and quantum transport in oxides and provides a novel and practical strategy to overcome the mobility–stability tradeoff in next-generation oxide transistors.