High performance RF FETs using high-k dielectrics on wafer-scale quasi-free-standing epitaxial graphene

We explore the effect of processing on graphene/metal ohmic contact resistance, the integration of high-κ dielectric seeds and overlayers on carrier transport in epitaxial graphene, and directly demonstrate the importance of buffer elimination at the graphene/silicon carbide (0001) interface for high frequency applications. We present a robust method for forming high quality ohmic contacts to graphene, which improves the contact resistance by nearly six thousand times compared to untreated metal/graphene interfaces. Optimal specific contact resistance for treated Ti/Au contacts is found to average < 100 Ohm-μm. Additionally, we introduce a novel seeding technique for depositing dielectrics by atomic layer deposition that utilizes direct deposition of high-κ seed layers and can lead to an increase in Hall mobility up to 70% from as-grown. Finally, we demonstrate that buffer elimination at the graphene/silicon carbide (0001) interface results in excellent high frequency performance of graphene transistors with current gain cutoff frequency > 130 GHz at 75 nm gate lengths.