Substrate dielectric effects on graphene field effect transistors

Abstract

Graphene is emerging as a promising material for future electronics and optoelectronics applications due to its unique electronic structure. Understanding the graphene-dielectric interaction is of vital importance for the development of graphene field effect transistors (FETs) and other novel graphene devices. Here, we extend the exploration of substrate dielectrics from conventionally used thermally grown SiO2 and hexagonal boron nitride films to technologically relevant deposited dielectrics used in semiconductor industry. A systematic analysis of morphology and optical and electrical properties was performed to study the effects of different substrates (SiO2, HfO2, Al2O3, tetraethyl orthosilicate (TEOS)-oxide, and Si3N4) on the carrier transport of chemical vapor deposition-derived graphene FET devices. As baseline, we use graphene FETs fabricated on thermal SiO2 with a relatively high carrier mobility of 10 000 cm2/(V s). Among the deposited dielectrics studied, silicon nitride showed the highest mobility, comparable to the properties of graphene fabricated on thermal SiO2. We conclude that this result comes from lower long range scattering and short range scattering rates in the nitride compared those in the other deposited films. The carrier fluctuation caused by substrates, however, seems to be the main contributing factor for mobility degradation, as a universal mobility-disorder density product is observed for all the dielectrics examined. The extrinsic doping trend is further confirmed by Raman spectra. We also provide, for the first time, correlation between the intensity ratio of G peak and 2D peak in the Raman spectra to the carrier mobility of graphene for different substrates.