Modeling of the Effect of Metal Islands in Hybrid Contacts to MoS2

Abstract

Contacts to ultra-thin layered semiconductors such as MoS 2 can be fabricated on either the top (basal plane) or edges of the semiconductor layers. Edge contacts may offer lower contact resistivity than top contacts, but there is a trade-off because the area of the edges is so low. A resistor circuit model has been used to explore hybrid contacts that offer lower contact resistance on multilayer semiconductors than either top-only or edge-only contacts. Metal islands from the hybrid contact protrude through the layers of semiconductor, creating edge contacts while a top contact is still present. Parameters are identified for three cases. When the edge contact resistivity is too high relative to the top contact resistivity, the metal islands increase the resistance of the hybrid contact above that of the top-only contact because of the reduced top contact area. An intermediate range of edge contact resistivities exists for which the hybrid contact provides a lower resistance than either a top-only or edge-only contact. In this case, smaller islands are better due to a reduced area to perimeter ratio. Finally, very low edge contact resistivities and high 2 semiconductor sheet resistances lead to hybrid contacts with resistances that are higher than those of the edge-only case. When adding islands is detrimental, current in the semiconductor beneath the contact must flow around the islands, leading to the increase in contact resistance.