Integrating high-quality dielectrics with one-nanometer equivalent oxide thickness on two-dimensional electronic devices

TL;DR

This paper presents a novel atomic layer deposition technique using a monolayer seeding layer to create ultrathin, high-quality dielectrics on 2D semiconductors, enabling high-performance low-power electronic devices.

Contribution

The study introduces a robust ALD method with a monolayer seeding layer for uniform high- dielectric films on 2D materials, achieving 1 nm EOT and improved device performance.

Findings

Ultrathin dielectrics down to 1 nm EOT achieved on 2D materials.

Enhanced device performance including RF operation at 60 GHz.

Reduced leakage current and interface states.

Abstract

Two-dimensional (2D) semiconductors are widely recognized as attractive channel materials for low-power electronics. However, an unresolved challenge is the integration of high-quality, ultrathin high-\k{appa} dielectrics that fully meet the roadmap requirements for low-power applications. With a dangling-bond free surface, the deposition of dielectrics by atomic layer deposition (ALD) on 2D materials is usually characterized with non-uniform nucleation and island formation, producing a highly porous dielectric layer with serious leakage particularly at the small equivalent oxide thickness (EOT) limit. Here, we report the robust ALD of highly uniform high-\k{appa} dielectric on 2D semiconductors by using ~0.3 nm-thick exclusively monolayer molecular crystal as seeding layer. Ultrathin dielectrics down to 1 nm EOT is realized on graphene, MoS2 and WSe2, with considerably reduced roughness, density of interface states, leakage current and improved breakdown field compared to prior methods. Taking advantage of the reduced EOT, we demonstrate graphene RF transistors operating at 60 GHz, as well as MoS2 and WSe2 complementary metal-oxide-semiconductor (CMOS) transistors with Vdd =0.8 V and ideal subthreshold swing (SS) of 60 mV/dec, 20 nm-channel-length MoS2 transistors with on/off ratio over 10^7. These studies highlight that our dielectric integration method is generally applicable for different 2D materials, and compatible with top-down fabrication process on large-area chemical vapor deposited films.