Negative differential resistance in graphene-based ballistic field effect transistor with oblique top gate

TL;DR

This paper reports the observation of negative differential resistance in graphene-based ballistic FETs with an oblique top gate, demonstrating room temperature NDR with high peak-valley ratio in defect-free monolayer graphene.

Contribution

It introduces a novel graphene FET design with an oblique top gate and demonstrates room temperature NDR in high-quality monolayer graphene.

Findings

NDR observed only in defectless graphene regions

Peak-valley ratio of 8 at room temperature

Ballistic transport lost in defective graphene areas

Abstract

Negative differential resistance (NDR) with room temperature peak-valley-ratio of 8 has been observed in a ballistic field-effect-transistor (FET) based on graphene, having an oblique top gate. Graphene FETs with a top gate inclination angle of 45 degrees and a drain-source distance of 400 nm were fabricated on a chip cut from a 4 inch graphene wafer grown by CVD. From the 60 measured devices, NDR was observed only in the regions where the CVD graphene displays the Raman signature of defectless monolayers. In other specific positions on the wafer, where graphene quality was not high enough and the Raman signature indicated the presence of defects, the ballistic character of transport is lost and the graphene FETs display nonlinear drain-voltage dependences tuned by the top and back gate voltage.