Device applications of epitaxial graphene on silicon carbide
Graphene is a sp 2 bonded sheet of carbon atoms with honeycomb symmetry that shows non-dispersive transport characteristics. In graphene, electrons move as relativistic Dirac particles with a velocity ∼10× higher than in a conventional semiconductor. Carrier mobilities more than 100 000 cm 2 /V·s [1,2] and saturation velocities of about 5 × 10 7 cm −2 s −1 have been reported  . These properties in addition to a high current density up to 10 9 A/cm 2 and high thermal conductivity up to 5000 W
... m −1 K −1  make it extremely appealing for applications in electronics. The two-dimensional nature of graphene enables tight control of the carrier density using the field effect  , and permits the use of conventional semiconductor processing techniques. It is worth noting that most of these extraordinary properties are related to pristine graphene  under slightly idealized conditions such as graphene exfoliated from highly oriented pyrolitic graphite (HOPG), suspending the sheets between metal leads, or using an ultra flat and inert substrate as BN. In research and technology, graphene is used in more complex structures, and at conditions that are determined by the targeted applications. For instance, electrical transport is subject to a variety of scattering events       . The type of scattering mechanism that dominates in a specific sample could be derived from the magnitude of the carrier mobility (µ), and its dependence on temperature (T) and carrier density (n)  . Therefore, mobilities greater than 100 000 cm 2 /V·s are known to indicate scattering that is dominated by acoustic phonons, where µ AC ∼ 1/n [1, 2, 9] . This is typical for graphene when the substrate is removed and it is heated in order for the adsorbates to volatilize. Long-range Coulomb scattering results in mobilities of the order of 1000-10 000 cm 2 /V·s that are independent of carrier density, n [8, 10, 11] . It is related with charge impurities on graphene or more likely at the supporting insulator substrate. Neutral defects become significant in either highly defective samples or at high carrier densities and mobility dominated by short-range scatter, µ SR ∼ 1/n [7, 11, 14, 15] . In most of the electronic applications graphene is supported by a dielectric substrate (typically SiO 2 or high-k dielectrics) or by semi-insulating SiC. In this cases the values of the electron mean free path l gr and mobility observed in Abstract Graphene has become an extremely hot topic due to its intriguing material properties allowing for ground-breaking fundamental research and applications. It is one of the fastest developing materials during the last several years. This progress is also driven by the diversity of fabrication methods for graphene of different specific properties, size, quantity and cost. Graphene grown on SiC is of particular interest due to the possibility to avoid transferring of free standing graphene to a desired substrate while having a large area SiC (semi-insulating or conducting) substrate ready for device processing. Here, we present a review of the major current explorations of graphene on SiC in electronic devices, such as field effect transistors (FET), radio frequency (RF) transistors, integrated circuits (IC), and sensors. The successful role of graphene in the metrology sector is also addressed. Typical examples of graphene on SiC implementations are illustrated and the drawbacks and promises are critically analyzed.