Effects of multiple buffer layers on structural electronic properties of GaN growth by atmospheric pressure Organometallic Vapor Phase Epitaxy

High-quality GaN epitaxial films have been grown on sapphire by organometallic vapor phase epitaxy using multiple-pair buffer layers. Each pair of buffer layers consists of a thin GaN nucleation layer grown at a low temperature around 500°C and a thick GaN epitaxial layer around 4 μm thick grown at a high temperature around 1000°C. The sample with four-pair buffer layers showed much improved GaN epitaxial films, as compared to the sample with only one-pair of buffer layers. The better qualities include narrower full width at half maximum of 150 arc-s and stronger intensity in double-crystal X-ray diffraction, higher electron mobility of 420 cm2 V-s−1, lower background concentration of 3×1017 cm−3, and lower etch-pit density of mid-105 cm−2.