Epitaxial Graphene As an Electrode Material: A Transistor Testbed for Organic and All-Carbon Semiconductors

We present a transistor testbed for novel organic and all-carbon electronic materials. Epitaxial graphene on silicon carbide (SiC) is used as source and drain electrodes. The gate is implemented as a bottom gate. Due to Fermi level pinning at the graphene/SiC interface, the gate is effective in the channel area only. The semiconductor above source and drain contacts and the graphene itself are unaffected by the bottom gate. This leads to a clear distinction of electronic properties in the sharply separated channel and contact areas. As an example, we investigate P3HT and fullerene films, representing standard p-type and n-type semiconducting materials. In particular, for P3HT an ohmic contact to graphene was observed, and an accurate and consistent determination of transistor parameters was achieved. The fullerene transistor showed a high on/off ratio of 3 x 10(3). The testbed offers the opportunity to determine semiconductor parameters of novel materials under very well-defined conditions.