Lattice-plane bending angle modulation of Mg-doped GaN homoepitaxial layer observed by X-ray diffraction topography

Abstract

We have studied the lattice-plane modulation of Mg-doped GaN homoepitaxial layers by X-ray diffraction topography. X-ray rocking curve images and full-width at half maxima images of a 2 inch GaN wafer were obtained by an image stacking method. Low frequency components evaluated from Fourier transformations of the X-ray rocking curves tended to increase as the Mg-doping concentration increased, which indicates an increase of film lattice modulation. For Mg-dopant concentrations greater than 10¹⁹ cm⁻³, the film lattice-plane changed from a convex to concave shape and became wrinkled. We attribute this lattice-plane modulation to the relaxation of strain in the in-plane direction after the generation of dislocations by Mg doping.