The Optimal Electronic Structure for High-Mobility 2D Semiconductors: Exceptionally High Hole Mobility in 2D Antimony.

Two-dimensional (2D) semiconductors have very attractive properties for many applications such as photoelectrochemistry. However, a significant challenge that limits their further developments is the relatively low electron/hole mobility at room temperature. Here using the Boltzmann transport theory with the scattering rates calculated from first-principles that allow us to accurately determine the mobility, we discover an exceptionally high intrinsic mobility of holes in monolayer antimony (Sb), which is ∼1330 cm2 V-1 s-1 at room temperature, much higher than the common 2D semiconductors including MoS2, InSe, and black phosphorus in monolayer form, and is the highest among 2D materials with a band gap of >1 eV reported so far. Its high mobility and the moderate band gap make it very promising for many applications. By comparing the 2D Sb with other 2D materials in the same group, we find that the high mobility is closely related with its electronic structure, which has a sharp and deep valence band valley, and, importantly, located at the Γ point. This electronic structure not only gives rise to a high velocity for charge carriers but also leads to a small density of states for accepting the scattered carriers, particularly by eliminating the valley-valley and peak-valley scatterings that are found to be significant for other materials. This type of electronic structure thus can be used as a target feature to design/discover high-mobility 2D semiconductors. Our work provides a promising material to overcome the mobility issue and also suggests a simple and general principle for high-mobility semiconductor design/discovery.