An approach was reported for using AlN/AlGaN superlattices for threading-dislocation density reduction when growing thick high-quality AlGaN films on sapphire. By using X-ray diffraction measurements, and etch-pit counting by atomic force microscopy, it was shown that the insertion of AlN/AlGaN superlattices suppressed mosaicity and decreased the threading dislocation density by 2 orders of magnitude. The dislocation densities deduced from X-ray diffraction results, and those deduced by chemical etching, were in good agreement.

AlN/AlGaN Superlattices as Dislocation Filter for Low Threading-Dislocation Thick AlGaN Layers on Sapphire. H.M.Wang, J.P.Zhang, C.Q.Chen, Q.Fareed, J.W.Yang, M.A.Khan: Applied Physics Letters, 2002, 81[4], 604-6

Figure 2

Permeation Data for D in (Al,Ti)N Layer

(yielding an activation energy for diffusion of 0.37eV)