In Situ Engineering of Vertical Indium Gradients via Sputtering Kinetics for High-Performance IGZO Channel-All-Around Transistors

Vertical channel-all-around (VCAA) transistors based on indium-gallium-zinc oxide (IGZO) are promising candidates for monolithic 3D integration. However, they inherently suffer from contact resistance asymmetry and trade-offs between the drive-current and leakage due to uniform channel doping limitations. This study demonstrates a high-performance VCAA FET featuring a vertical indium-gradient channel, engineered via in situ resputtering kinetics during deposition. The modulated band structure reduces the Schottky barrier height (ϕ_BN) at the bottom electrode, achieving a record high on-current of 82.8 μA/μm and an ultralow contact resistivity of 8 × 10^-7 Ω·cm². We propose an analytical framework to decouple top and bottom contact resistances, revealing that transport behavior is driven by asymmetric ϕ_BN and drain-induced barrier thinning (DIBT). This work provides fundamental insights into vertical transport in oxide semiconductors and offers a scalable pathway for engineering contact symmetry in vertical logic devices.