Combined MOCVD and MBE growth of GaN on porous SiC

GaN films have been grown homoepitaxially by MOCVD on MBE-grown GaN template layers, using both porous and nonporous SiC substrates. The effect of the porous SiC substrates on dislocations in the MBE and MOCVD GaN layers has been studied using TEM and x-ray characterization. A reduction in dislocation density from ≥1×10¹⁰ cm^-2 in the MBE template to 2.5×10⁹ cm^-2 at the top of the MOCVD film is found, with similar final values in the MOCVD films for both porous and nonporous substrates. We discuss various mechanisms by which dislocation density is reduced in the MOCVD layers.