GaN epilayers were prepared on sapphire substrate by Hot Wall Epitaxy
technique using Ga and NH3 gas as source materials. The initial layer
was needed to grow a high quality GaN epilayers on a sapphire substrat
e, because it has an important affect in the crystallinity of the epil
ayers. We grow the separated and combined initial layers on nitrided s
apphire substrate and performed the measured. We certify that from the
se data the crystallinity of GaN epilayers grown on separated initial
layers was better than that on combined initial layer.