Dislocation defects in GaN epilayers grown on Si (100) substrates by metal-organic chemical-vapor deposition

Dislocation defects in GaN epilayers grown on Si substrates were investigated using cathodoluminescence (CL) and atomic force microscopy (AFM). The dislocation densities of the films were deduced from two-dimensional CL image measurements and ranged from 1 x 10¹¹ cm^-2 to 5 x 10¹¹ cm^-2. These values are larger than those reported for GaN epilayers grown on sapphire substrates. The surface morphology and dislocations in the GaN epilayers were investigated by using AFM. From a comparative study of the CL and the AFM measurements, the GaN epilayers with lower dislocation densities are seen to have good surface morphologies with smaller densities of surface defects.