Internal Quantum Efficiency of InGaN/GaN Led Structures Grown on a Patterned Sapphire Substrate

Effect of a patterned sapphire substrate on the increase of external quantum efficiency in "blue" InGaN/GaN LED structures is studied. It is shown that in structures with high internal quantum efficiency (no less than 60%), an increase of the external quantum efficiency is due to an increase of the coefficient of the radiation output from the crystal. Epitaxial growth of GaN on a sapphire substrate with an array of elements of pyramidal shape with a base of 900 nm and a period of 1200 nm allows to increase by 75% the coefficient of the radiation output.