Manish Chhowalla, University of Cambridge
Ultra Clean van der Waals Contacts Using Indium Alloys on Two-Dimensional Semiconductors
Written by Tomojit Chowdhury
Contact configuration is one of the most crucial parameters that dictates the over-all performance of transistor devices. The Chhowalla Group at the University of Cambridge proposed an alternative contact design that exhibited improved device performance. They chose indium as their contact metal due to its exceptionally low melting temperature (156˚C) compared to other commonly known contact metals, such as gold (Au) and titanium (Ti). “Clearly indium electrodes can be patterned on atomically thin transition metal dichalcogenide (TMD) sheets under very gentle evaporation conditions,” said Chhowalla, alluding to the “soft” physical nature of the metal. In addition, he showed how platinum (Pt) and indium (In) could be alloyed under mild conditions, and thus could be simultaneously deposited atop layered TMDs ensuring “ultra-clean” contacts with atomically sharp metal-semiconductor (Schottky) interface. Such “work function engineering of metal contacts on 2D semiconductors” allowed fabrication of field-effect transistor devices with exceptional carrier mobility.