Ballistic transport in black phosphorus transistors

As a strong candidate for future electronics, atomically thin black phosphorus (BP) has attracted great attention in recent years due to its tunable bandgap and high mobility. Here we show that the transport properties of BP device under high electric field can be improved greatly by the interface engineering of high-quality HfLaO dielectrics and transport orientation. By designing the device channels along the lower effective mass armchair direction, a record high drive current up to 1.2 mA/μm at 300 K and 1.6 mA/μm at 20 K can be achieved in a 100 nm back-gated BP transistor, surpassing any two-dimensional semiconductor transistors reported to date. The highest hole saturation velocity of 1.5×10⁷ cm/s is also achieved at room temperature. Ballistic transport shows a record high 36% and 79% ballistic efficiency at room temperature and 20 K, respectively, which are also further verified by theoretical simulations.