Improved MOCVD growth of GaN on Si-on-porous-silicon substrates

The mechanism of the poor surface morphology of MOCVD-grown GaN on porous Si (PSi) substrates was explored. Transmission electron microscopy suggests that a vacancy growth of pores starts, which is accompanied by the migration of the top surface of the PSi layer during the initial growth stage of GaN on the AlN inter layer. This causes a lot of pits on top GaN and wavy interface between GaN of the PSi layer, deteriorating the poor surface morphology. The epitaxial Si layer on PSi is effective in suppressing the migration of the top surface of the PSi layer. The GaN film on the epitaxial-Si/PSi shows a mirror surface with pits-free and very few cracks. No voids at the interface between the AlN IL and Si/PSi substrate are observed.