Correlation between threading dislocations in highly mismatched GaN heteroepitaxial layers

A simple model that establishes a quantitative measure for the positional correlation degree of threading dislocations (TDs) in heteroepitaxial layers is proposed. Accordingly, analyzing the linewidth of the Gaussian fit that follows the experimental rocking curve (RC), we obtained the correlation degree of screw and edge TDs in GaN epitaxial layers grown on sapphire substrate. Calculating the numerical integral using both the standard Wilkens correlation parameter, M, and the new one, S, and comparing the numerical results with the experimental diffraction patterns for three samples of GaN epitaxial films with different thicknesses, we demonstrate that the newly determined correlation parameter is correct.