High-Performance Enhancement-Mode Ultra-thin ALD-Grown InWSnO Transistors Enabled by W/Sn Co-Engineering and Back-Channel Passivation

We report atomic layer deposition-grown indium–tungsten–tin oxide (IWTO) thin-film transistors that effectively circumvent the conventional on-current–threshold voltage (ION–VTH) trade-off in atomically thin oxide semiconductors. A W/Sn co-engineered IWTO channel is developed by systematically varying the W concentration from 1 to 3 at.% while maintaining a fixed In/Sn cycle ratio, enabling balanced charge transport and threshold-voltage (VTH) stability in ∼2 nm channels. To ensure long-term reliability, an ozone-based back-channel passivation (BCP) process was implemented, suppressing environmental instability without compromising the intrinsic electronic properties. Devices optimized with a 1 at.% W concentration with BCP exhibit superior electrostatic control, characterized by a steep subthreshold swing, negligible hysteresis, and ultra-low leakage current. Notably, these performance advantages persist upon scaling the channel length (LCH) down to 200 nm, maintaining a high-drive current of 338 μA/μm (at VDS = 1 V) with the enhancement-mode operation (VTH > 0 V) and robust bias-stress stability. This work establishes a scalable material platform for high-performance oxide electronics compatible with back-end-of-line applications.