Improvement in the Crystalline Quality of Epitaxial GaN Films Grown by MOCVD by Adopting Porous 4H-SiC Substrate

Epitaxial GaN films were grown on a porous 4H-SiC (PSC) substrate at 1080°C using metallorganic chemical vapor deposition (MOCVD). The GaN films showed an improved epitaxial quality with the smallest threading dislocation density being demonstrated for growth on the PSC substrates, when compared to that on standard 4H-SiC substrates as well as on sapphire The full width at half-maximum values of the reflection in high-resolution X-ray diffraction of the GaN films grown on sapphire, the standard 4H-SiC, and the PSC substrate under a skew symmetric diffraction geometry were 388, 313, and 224 arcsec, respectively, showing that PSC is effective in reducing the threading edge dislocation density. 224 arcsecs is the smallest ever reported for GaN films. This may be due to a relaxation of the mismatch in the lattice parameter by the lower thermal strain in the GaN films due to the porous structure of the PSC substrate.