Layer-by-Layer Epitaxy of Multilayer MoS2 Wafers

TL;DR

This paper reports the successful layer-by-layer epitaxial growth of high-quality multilayer MoS2 wafers, enabling improved electronic device performance and precise control over layer number, advancing the practical application of 2D MoS2 in electronics.

Contribution

It introduces a novel layer-by-layer epitaxy method for growing high-quality multilayer MoS2 wafers with controlled layer numbers up to six.

Findings

Enhanced field-effect mobility in multilayer MoS2 transistors.

Record-high on-current densities achieved in trilayer MoS2 FETs.

Systematic analysis of atomic structures and electronic properties.

Abstract

Two-dimensional (2D) semiconductor of MoS2 has great potential for advanced electronics technologies beyond silicon1-9. So far, high-quality monolayer MoS2 wafers10-12 are already available and various demonstrations from individual transistors to integrated circuits have also been shown13-15. In addition to the monolayer, multilayers have narrower band gaps but improved carrier mobilities and current capacities over the monolayer5,16-18. However, achieving high-quality multilayer MoS2 wafers remains a challenge. Here we report the growth of high quality multilayer MoS2 4-inch wafers via the layer-by-layer epitaxy process. The epitaxy leads to well-defined stacking orders between adjacent epitaxial layers and offers a delicate control of layer numbers up to 6. Systematic evaluations on the atomic structures and electronic properties were carried out for achieved wafers with different layer numbers. Significant improvements on device performances were found in thicker-layer field effect transistors (FETs), as expected. For example, the average field-effect mobility ({\mu}FE) at room temperature (RT) can increase from ~80 cm2V-1s-1 for monolayer to ~110/145 cm2V-1s-1 for bilayer/trilayer devices. The highest RT {\mu}FE=234.7 cm2V-1s-1 and a record-high on-current densities of 1.704 mA{\mu}m-1 at Vds=2 V were also achieved in trilayer MoS2 FETs with a high on/off ratio exceeding 107. Our work hence moves a step closer to practical applications of 2D MoS2 in electronics.