Electrode Engineering in MoS2 MOSFET: Different Semiconductor/Metal Interfaces

The formation of Ohmic contact between metal electrode and 2D semiconductor channel is considered a key factor for performance improvement of 2D metal-oxide-semiconductor field-effect transistors (MOSFET). However, the Schottky barrier at the metal electrode/2D semiconductor interfaces cannot be lowered effectively due to the pinning effect of Fermi levels, which makes it hard to obtain lower Ohmic contact resistance. Until now, although physical transfer metal electrode or inserted tunneling layer has been reported to get rid of the Fermi-level pinning effect, these different designs of electrode engineering are not systematically compared. To serve better Ohmic contact, three different designs of electrode engineering are employed in 2D MoS2 MOSFET: evaporating Ag electrode on MoS2, transferring MoS2 to Ag electrode, and inserting ultrathin AlOx tunneling layer. Our experimental results demonstrate that the transferring MoS2 to Ag electrode in 2D MoS2 MOSFET can obtain the lowest contact resistance and Schottky barrier of 0.45 omega cm and 12.8 meV, respectively. On this basis, photodiodes with obvious rectifying behavior are fabricated using schemes of electrode engineering, due to their different Schottky barrier high. The detailed contrastive analysis in our three different designs of electrode engineering can provide valuable guidance to optimize the performance of 2D semiconductor MOSFET.