High field transport of high performance black phosphorus transistors

Black phosphorus is a layered material stacked together by weak van der Waals force with a direct bandgap and highly anisotropic electrical characteristics. Most of the previous reports focus on the low-field mobility of transistors based on SiO₂ back gate dielectrics. Recently, black phosphorus transistors encapsulated with hexagonal boron nitride have been demonstrated with greatly improved mobility at low temperatures. However, this approach requires multiple dry transfer methods using both black phosphorus and boron nitride flakes, which are only available in small crystal sizes. Here, we demonstrated high performance black phosphorus transistors using atomic layer deposited high-κ HfO₂ as a back gate dielectric. The maximum drain current density reaches 480 μA/μm at 300 K and a record high drain current 906 μA/μm at 20 K in a short channel 100 nm device based on HfO₂, exhibiting excellent current-carrying capability and high field strength. Moreover, a side-by-side comparison on important figures-of-merit is carried out systematically for transistors based on HfO₂ with those based on conventional SiO₂, showing more than 50% performance improvement in mobility and over 8 times reduction in interface trap density.