On Low-Resistance Contacts to 2-D MoTe2 by Crystalline Phase Junctions

Low contact resistance to 2-D semiconductor materials plays a critical role on their device applications. It has been experimentally demonstrated recently that the crystalline phase homojunctions between the 1T' metallic and 2H semiconducting phases of 2-D transition metal dichacolgenide (TMDC) materials can be formed by a variety of fabrication techniques. A multiscale simulation approach that integrates atomistic ab initio simulations with quantum transport calculations based on the nonequilibrium Green's function formalism is used to examine the contact properties of the crystalline phase junctions of monolayer MoTe2. It is shown that the following mechanisms can contribute to the low contact resistance of crystalline phase metal-semiconductor junctions of 2-D materials. First, the electric field is significantly enhanced at the 2-D phase junction interface due to the extremely thin body, which results in a thin Schottky barrier. Second, the coupling of electron wave functions cross the 1T'-2H junction interface is strong. Third, different from 3-D bulk metal-semiconductor junctions, metal-induced band gap states (MIGS) do not pin the Fermi level in the 2-D material junctions due to low dimensionality of the MIGS charge. The results provide insights into the possibility and limits of achieving low-contact-resistance contacts to 2-D TMDC semiconductors by using crystalline phase metal-semiconductor junctions.