GaN/SiC heterojunction diodes have been fabricated and characterized. Epitaxialn-type GaN films were grown using metalorganic chemical vapor deposition (MOCVD) and electron cyclotron resonance assisted molecular beam epitaxy (ECR-MBE) onp-type Si-face 6H-SiC wafers. TheI–Vcharacteristics have diode ideality factors and saturation currents as low as 1.2 and10−32A/cm2,respectively. The built-in potential in the MOCVD- and ECR-MBE-grownn-pheterojunctions was determined from capacitance–voltage measurements at 2.90±0.08 eV and 2.82±0.08 eV, respectively. From the built-in potential the energy band offsets for GaN/SiC heterostructures are determined at&Dgr;EC=0.11±0.10eV and&Dgr;EV=0.48±0.10eV. ©1998 American Institute of Physics.