Large and anisotropic carrier mobility in monolayers of the MA2Z4 series (M = Cr, Mo, W; A = Si, Ge; and Z = N, P)

The recent discovery of synthetic two-dimensional materials has opened up a new paradigm for exploring novel transport and optical properties, beyond those found in naturally occurring materials. Here, we present a detailed investigation of the acoustic phonon limited intrinsic carrier mobility in MA2Z4 series (M = Cr, Mo, W; A = Si, Ge; and Z = N, P) monolayers. We find that out of the twelve monolayers studied, only two are metallic (CrGe2N4 and CrGe2P4), and the rest of them are semiconducting. We demonstrate that the carrier mobilities in these monolayers are anisotropic and show a large variation, ranging from a small value of ∼90 cm2 V-1 s-1 to a large value of ∼104 cm2 V-1 s-1. In addition, we show that strain engineering in these materials can further change the electronic band structure drastically, and change the carrier mobilities by up to a factor of 20. Our detailed and systematic study provides a useful platform for designing electronic devices based on the MA2Z4 family of materials.