Electron Microscopy Investigation of the Role of Surface Steps in the Generation of Dislocations during MOCVD Growth of GaN on 4H-SiC

Through the use of specially-prepared on-axis SiC substrates with patterned mesa tops completely free of atomic-scale surface steps, we have previously reported the growth of highquality GaN heteroepitaxial films with greatly reduced threading dislocation densities on the order of 107/cm2. In these films, we reported a defect substructure in which lateral a-type dislocations are present in the nucleation layer but do not bow into threading …