Effects of Al-containing Intermediate III-nitride Strained Multilayers on the Threading Dislocation Density and Optical Properties of GaN Films

We report the influence of intermediate AlN/GaN, AlGaN/GaN or AlN/AlGaN strained multilayer structures on the threading dislocation (TD) density and optical properties of GaN films. A series of GaN films were deposited at 1050°C on (0001) sapphire substrates using intermediate AlN/GaN, AlGaN/GaN or AlN/AlGaN strained multilayer structures. Etching pit density (EPD) counts and transmission electron microscopic (TEM) studies show that the implementation of AlN/GaN and AlGaN/GaN in GaN films enables the blocking of TDs in the films very efficiently. Photoluminescence (PL) measurements exhibit the increment of near band edge emission intensity in the GaN films having Al_0.5Ga_0.5N/GaN or AlN/GaN intermediate strained multilayer structures. Cross-sectional TEM observations show that TD annihilation and de-multiplication processes play important roles in the TD density reduction in the GaN films having Al-containing strained multilayer structures.