As a third-generation semiconductor material, gallium nitride (GaN) features superior bandgap (far higher than silicon and silicon carbide), thermal conductivity, electron mobility, and on-resistance. Due to high N dissociation pressure during GaN growth at high temperatures, large-sized GaN single crystals are hard to obtain—thus, preparing epitaxial GaN films on heterogeneous substrates becomes the main method for GaN material and device research. Common growth methods include HVPE, MBE, and MOCVD. Most commercial devices are based on GaN heteroepitaxy, with SiC, Si, and Sapphire as primary substrates.