Epitaxial growth of GaN films on unconventional oxide substrates

GaN is a unique material with outstanding optoelectronic properties and is suitable for application in light-emitting diodes (LEDs), laser diodes (LDs), high electron mobility transistors (HEMTs), etc. Usually, GaN films are grown on sapphire substrates. However, due to the relatively large lattice and thermal expansion coefficient mismatches between GaN and sapphire, to obtain high-performance and high-power GaN-based devices is still highly desired. In this regard, many researchers have tried hard to grow GaN films on unconventional oxide substrates other than sapphire, which share relatively small lattice and thermal expansion coefficient mismatches with GaN. This review focuses on the recent progress of the epitaxial growth of GaN films on unconventional oxide substrates. The perspectives for the epitaxial growth of GaN films on unconventional oxide substrates are also discussed.