Graphene on Silicon Hybrid Field-Effect Transistors

TL;DR

This paper introduces a novel graphene-on-silicon heterostructure technology for solution-gated transistors, analyzing their electrical properties and developing a physics-based model to explain hybrid charge transport behavior.

Contribution

The work presents a new fabrication method for graphene-on-silicon FETs and a comprehensive model explaining their unique hybrid electrical characteristics.

Findings

Hybrid devices exhibit combined features of graphene and silicon.

Graphene acts as a shield, influencing potential distribution and subthreshold behavior.

The model accurately predicts experimental results and explains the screening effect.

Abstract

The combination of graphene with silicon in hybrid devices has attracted attention extensively over the last decade. Most of such devices were proposed for photonics and radiofrequency applications. In this work, we present a unique technology of graphene-on-silicon heterostructures and their properties as solution-gated transistors. The graphene-on-Silicon field-effect transistors (GoSFETs) were fabricated exploiting various conformations of drain-source regions doping and channel material dimensions. The fabricated devices were electrically characterized demonstrating hybrid behavior with features specific to both graphene and silicon. Although GoSFET's transconductance and carrier's mobility were found to be lower than in conventional silicon and graphene field-effect transistors (SiFETs and GFETs), it was demonstrated that the combination of both materials within the hybrid channel contribute uniquely to the charge carrier transport. A comprehensive physics-based compact modeling was specifically developed, showing excellent agreement with the experimental data. The model is employed to rationalize the observed hybrid behavior as the theoretical results from the electrostatics and the carrier transport under a drift-diffusion approach show that graphene acts as a shield for the silicon channel, giving rise to a non-uniform potential distribution along it, especially at the subthreshold region. This graphene screening effect is shown to strongly affect the device subthreshold swing when compared against a conventional SiFET due to a non-negligible diffusion current in this operation regime.