Growth mechanism in the multiple buffer layer of GaN on sapphire by organometallic vapor phase epitaxy

[[abstract]]High-quality GaN epitaxial layers with a multiple-pair buffer layer have been grown on sapphire substrates in a separate-flow reactor by metalorganic chemical vapor deposition. Each pair of buffer layers consists of a 300 Å thick GaN nucleation layer grown at a low temperature of 525°C and a 1-4 μm thick GaN epitaxial layer grown at a high temperature of 1000°C. The GaN samples with a multiple-pair buffer layers are characterized by etch-pit density and cross-section TEM measurements. In this experiment, the regions grown on multiple buffer layers were thoroughly examined. Cross-section TEM clearly revealed characteristic defects along the [112¯0] direction in the various pairs of buffer-layer grown regions. We observed the interface of buffer layer and buffer layer, where most vertical dislocations can be terminated in the interface, and few dislocation were repropagated in the subsequent buffer-layer growth. The influence of multiple buffer structure and the dislocation distribution near the buffer-layer interface are discussed[[fileno]]2030154030003[[department]]電機工程學