Threading dislocation annihilation in the GaN layer on cone patterned sapphire substrate

• The LED structure on PSS was grown by MOCVD.
• The distribution of defects in GaN film grown on PSS was investigated by TEM.
• The main mechanism of TDs reducing on PSS was revealed.

The microstructure of an epilayer structure for the blue light-emitting diode grown on a cone patterned sapphire substrate was characterized by high-resolution X-ray diffraction, atomic force microscopy and transmission electron microscopy (TEM). Cross-sectional TEM revealed that most of the dislocations, which originated from planar region, propagated laterally toward the cone region during the lateral growth process. This change of the propagation direction prevented the dislocations from penetrate the epitaxy film and thus principally led to a drastic reduction in the threading dislocation density in GaN films. Particularly, we proposed that the six {11‾01} semipolar facets play a very important role during the bending process.