Defect Structure and Evolution of GaN-Based Light-Emitting Diodes on Planar and Cone-Patterned Sapphire Substrates

Epitaxial layers of GaN and InGaN/GaN multi-quantum well light emitting diodes (LEDs) were prepared both on cone-shaped patterned sapphire substrates and conventional sapphire substrates. The mechanism of nucleation of GaN epilayers was studied using metallographic and atomic force microscope images of the surface of GaN epilayers, and the internal factors of cone-shaped patterned sapphire substrates that accelerate GaN transverse growth and improve the quality of epitaxial layers were analyzed. The microstructural properties of GaN epitaxial layers grown on a patterned sapphire substrate were studied in detail using transmission electron microscopy to determine the distribution and growth. The surface morphology of p-GaN was characterized by scanning electron microscopy, and some other information about the defects was obtained. The full width at half maximum of electroluminescence spectra of LED grown on the patterned sapphire substrate is small, and its monochromaticity is good.