▎ 摘　　要

Vertical diodes of epitaxial graphene on n(-) 4H-SiC were investigated. The graphene Raman spectra exhibited a higher intensity in the G-line than the 2D-line, indicative of a few-layer graphene film. Rectifying properties improved at low temperatures as the reverse leakage decreased over six orders of magnitude without freeze-out in either material. Carrier concentration of similar to 10(16) cm(-3) in the SiC remained stable down to 15 K, while accumulation charge decreased and depletion width increased in forward bias. The low barrier height of 0.08 eV and absence of recombination-induced emission indicated majority carrier field emission as the dominant conduction mechanism. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4712621]