Next generation field-effect transistors based on 2D black phosphorus crystal

Two-dimensional (2D) crystals emerge as a new class of semiconducting material which may potentially revolutionize future electronic devices. Unlike graphene, black phosphorus (BP) is a semiconductor which has a predicted direct bandgap that can be tuned from 0.3 eV in its bulk form to 2.0 eV when reduces to a monolayer thinness. The presence of a bandgap in BP makes it advantageous over graphene in facilitating good transistor switching action. Here, field-effect transistors based on multi-layer BP and high-k gate dielectric (HfO2) are demonstrated using CMOS-compatible processes. Respectable transistor characteristics are achieved including a room temperature hole mobility of ∼413 cm²/Vs and a subthreshold slope of ∼200 mV/dec. Good ohmic contacts with a low Schottky barrier height of ∼130 meV is realized using nickel (Ni), which can be further reduced to ∼20 meV through thermal annealing. The potential of achieving low contact resistance coupled with enhanced carrier transport properties makes BP a promising channel material for next generation nanoelectronic device applications.