Refractory metals as alternate contact metals for 2D/3D Heterostructures

Vertical three-terminal complex devices based on 2D/3D heterostructures require metal contacts that can withstand high temperature and harsh chemical environment brought about by the 2D/3D material synthesis that follows the metal contact fabrication [1, 2, 3]. Refractory metals, such as Mo, W and Cr, are candidates for this purpose and have been used by our team for the fabrication of contacts to the Base (MoS₂) in a vertical GaN/MoS₂/GaN heterojunction bipolar transistor. Since refractory metals exhibit endurance toward high temperature, abrasion and degradation, they are expected to form sharp, high-quality interface with 2D materials. Motivated by this, we have performed first principle simulation study of refractory metals/2D/3D systems and analyzed structural and electronic properties, such as binding energies, Schottky barrier heights (SBH), and mid-gap charge densities, and investigated the feasibility of using refractory metals as contact metals in 2D/3D systems. Furthermore, we have made an attempt to establish a correlation between the metal type and degree of Fermi level pinning using theoretical as well as in-house experimental data. 1. ACS Nano 10, 3580, 2016, 2. App. Phys. Lett 111, 051602, 2017, 3, 2D Materials 5, 045016, 2018