Why InO Can Make 0.7 nm Atomic Layer Thin Transistors.

In this work, we demonstrate enhancement-mode field-effect transistors by an atomic-layer-deposited (ALD) amorphous InO channel with thickness down to 0.7 nm. Thickness is found to be critical on the materials and electron transport of InO. Controllable thickness of InO at atomic scale enables the design of sufficient 2D carrier density in the InO channel integrated with the conventional dielectric. The threshold voltage and channel carrier density are found to be considerably tuned by channel thickness. Such a phenomenon is understood by the trap neutral level (TNL) model, where the Fermi-level tends to align deeply inside the conduction band of InO and can be modulated to the bandgap in atomic layer thin InO due to the quantum confinement effect, which is confirmed by density function theory (DFT) calculation. The demonstration of enhancement-mode amorphous InO transistors suggests InO is a competitive channel material for back-end-of-line (BEOL) compatible transistors and monolithic 3D integration applications.