Direct observation of ballistic transport in vertical direction of Black Phosphorus

Ballistic transport is the transport of carriers without scattering. In this regime, carriers travel freely and coherently in semiconductors and therefore the ballistic transport is highly desirable for the development of low power, high speed logic and quantum circuits. Due to its puckered lattice structure, the out-of-plane mobility of BP is comparable to in-plane mobility. Here, we report the direct observation of ballistic transport of BP in out-of-plane direction. The ballistic transport observed in vertical direction of BP is within a 3D framework which is different from 1D ballistic transport. Our results shed light on the development of efficiently facilitating carriers on the nanoscale.