Emergence of material-driven two-dimensional electron gas by thermodynamically robust layers in Al ₂ O ₃ /In ₂ O ₃ /Al ₂ O ₃ nanolaminate structures

In this study, the formation of two-dimensional electron gas (2DEG) at both Al₂O₃ (AO)/In₂O₃ (IO) and reversed IO/AO interfaces was demonstrated, enabling its integration into both channel-first and channel-last processes. While conventional reductive-precursor-driven 2DEG was generated at AO/IO interfaces, material-driven 2DEG was developed at IO/AO with no effect from the fabrication process. An optimized AO/IO nanolaminate showed a mobility of 217.9% (48.6 cm² V^-1 s^-1) relative to a single IO layer (22.3 cm² V^-1 s^-1). Angle-resolved X-ray photoelectron spectroscopy confirmed 2DEG formation at both post-deposited IO on AO (post-IO) and AO on pre-deposited IO (pre-IO) interfaces. Hall effect measurement on the nanolaminate reveals that pre-IO and post-IO contribute comparably to the reduction in sheet resistivity. This finding expands the application of 2DEG interfaces beyond the conventional channel-first process, paving the way for back-gated back-end-of-line transistors and 3D hole-channel fill architecture in next-generation devices.