The lack of GaN substrates is a limiting factor for the development of III-V nitride devices.Recently we proposed to use GaN/SiC epitaxial wafers, consisting of thin GaN layer depositedby hydride vapor phase epitaxy (HVPE) on SiC wafer, as substrates for subsequent growth of IIIVnitrides and devices development. These wafers are attractive to be used as substrates for GaNdevice fabrication because the GaN-based device structures can be grown on these wafers byhomoepitaxy without any buffer layer. Due to high SiC thermoconductivity and cleavagepossibility, these wafers are especially attractive for high-power electronic and optoelectronicapplications. In this paper, we focus on crystal structure, optical and electrical properties of GaNhomoepitaxial layers and p-n structures grown by HVPE on GaN/SiC epitaxial wafers. Newtypes of III-V nitride epitaxial wafers are described, insulating GaN/SiC epitaxial wafers andAIN/SiC epitaxial wafers.