Why In2O3 Can Make 0.7 nm Atomic Layer Thin Transistors?

TL;DR

This paper demonstrates the fabrication of enhancement-mode transistors using atomic-layer-deposited amorphous In2O3 channels as thin as 0.7 nm, revealing how atomic-scale thickness control influences electronic properties and device performance.

Contribution

It introduces a novel atomic-layer deposition method for creating ultra-thin amorphous In2O3 channels and explains the electronic behavior through the trap neutral level model and DFT calculations.

Findings

In2O3 channels as thin as 0.7 nm are achievable.

Channel thickness significantly affects threshold voltage and carrier density.

Quantum confinement influences the electronic properties of ultra-thin In2O3.

Abstract

In this work, we demonstrate enhancement-mode field-effect transistors by atomic-layer-deposited (ALD) amorphous In2O3 channel with thickness down to 0.7 nm. Thickness is found to be critical on the materials and electron transport of In2O3. Controllable thickness of In2O3 at atomic scale enables the design of sufficient 2D carrier density in the In2O3 channel integrated with the conventional dielectric. The threshold voltage and channel carrier density are found to be considerably tuned by channel thickness. Such phenomenon is understood by the trap neutral level (TNL) model where the Fermi-level tends to align deeply inside the conduction band of In2O3 and can be modulated to the bandgap in atomic layer thin In2O3 due to quantum confinement effect, which is confirmed by density function theory (DFT) calculation. The demonstration of enhancement-mode amorphous In2O3 transistors suggests In2O3 is a competitive channel material for back-end-of-line (BEOL) compatible transistors and monolithic 3D integration applications.