Investigation of Dielectric Overlayers and Device Processing on Transport and Performance of Epitaxial Graphene Field Effect Transistors

Open Access
Hollander, Matthew Johnston
Graduate Program:
Materials Science and Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
September 09, 2011
Committee Members:
  • Joshua Alexander Robinson, Thesis Advisor
  • graphene
  • transistors
  • FET
Graphene is a two-dimensional, one-atom thick layer of carbon atoms arranged in a honeycomb lattice. Exhibiting exceptional physical and electronic properties, graphene has attracted much recent attention as a novel material with potential applications in electronics and photonics. Although technical and scientific progress in the field of graphene has been rapid, many important issues remain as barriers to practical technological implementations of the material for electronic applications. Among these, device processing and materials integration without degradation or disruption of the excellent intrinsic properties of graphene are paramount. In this thesis, materials integration of metals and dielectrics with epitaxial graphene is investigated. Various contact metals, pre-treatments, and post-treatments are compared and a reproducible, robust process for producing low specific contact resistivity metal contacts to epitaxial graphene is developed. Similarly, various gate dielectrics and methods of deposition are investigated and a reproducible, robust technique for the deposition of thin, high-k gate dielectrics on epitaxial graphene is developed. This technique utilizes high-k oxide seeds evaporated directly from a high-purity oxide source using electron beam physical vapor deposition as a seed layer for subsequent growth by atomic layer deposition. Importantly, this method not only produces uniform, conformal, and robust gate dielectrics, but also leads to an improvement in the transport properties of the underlying graphene, which has been attributed to dielectric screening and a reduction of remote charged impurity scattering. Finally, the combination of optimized contacts and high-k gate dielectrics on epitaxial graphene has allowed for the demonstration of high extrinsic current gain cutoff frequencies for graphene radio-frequency transistors.