Contacts and Dielectrics for Two-Dimensional Semiconductors

In our presentation, we will address two related challenges for two-dimensional (2D) semiconductors for nanoelectronic applications: contacts and dielectrics. The first challenge is to make low-resistance contacts to 2D materials. Using modeling, we show how low-k surrounding dielectrics can drastically improve contact resistance, together with high channel doping and small Schottky barrier height. We show that the depletion width in a 2D material is determined by the surrounding dielectric and that image-force barrier lowering reduces the contact resistance by up to an order of magnitude when using a low-k dielectric. The second challenge we address is to make a low effective oxide thickness (EOT) gate stack on top of a mono-or few-layer 2D semiconductor channel without damaging the channel. Here, we present a list of 32 candidate 2D dielectrics starting from first principles calculations. We estimated the EOT and leakage current of each material and identified oxyhalides like LaOBr and LaOCl as promising high-k 2D dielectrics.