Effects of Plasma Treatment on Contact Resistance and Sheet Resistance of Graphene FET

Abstract

We investigated the effect of capacitively coupled Ar plasma treatment on contact resistance (<TEX>$R_c$</TEX>) and channel sheet resistance (<TEX>$R_{sh}$</TEX>) of graphene field effect transistors (FETs), by varying their channel length in the wide range from 200 nm to <TEX>$50{\mu}m$</TEX> which formed the transfer length method (TLM) patterns. When the Ar plasma treatment was performed on the long channel (<TEX>$10{\sim}50{\mu}m$</TEX>) graphene FETs for 20 s, <TEX>$R_c$</TEX> decreased from 2.4 to <TEX>$1.15k{\Omega}{\cdot}{\mu}m$</TEX>. It is understood that this improvement in <TEX>$R_c$</TEX> is attributed to the formation of <TEX>$sp^3$</TEX> bonds and dangling bonds by the plasma. However, when the channel length of the FETs decreased down to 200 nm, the drain current (<TEX>$I_d$</TEX>) decreased upon the plasma treatment because of the significant increase of channel <TEX>$R_{sh}$</TEX> which was attributed to the atomic structural disorder induced by the plasma across the transfer length at the edge of the channel region. This study suggests a practical guideline to reduce <TEX>$R_c$</TEX> using various plasma treatments for the <TEX>$R_c$</TEX> sensitive graphene and other 2D material devices, where <TEX>$R_c$</TEX> is traded off with <TEX>$R_{sh}$</TEX>.