The influence of template type and residual strain of the buffer layer on the structural properties of GaN/AlN superlattices was studied using high resolution X-ray diffraction. Using sapphire substrates, an effective thinning of the GaN quantum wells and the corresponding thickening of the AlN barriers were observed in superlattice structures grown on thin, strained AlN templates as compared with superlattice structures grown on thick, relaxed GaN templates. Moreover, a bimodal strain relaxation of superlattice structures in dependence of template type was observed. The superlattices grown on AlN templates relax predominantly by the formation of misfit dislocations, while the superlattices grown on GaN templates relax predominantly by cracking of the layers. These effects were explained in terms of the influence of residual strain in the buffer/template systems used for the growth processes of superlattice layers. A correlation was made between the strain state of the system and the cracking processes, the dislocation density, the radius of curvature and the layer thickness.

Influence of Template Type and Buffer Strain on Structural Properties of GaN Multilayer Quantum Wells Grown by PAMBE, an X-Ray Study. V.P.Kladko, A.V.Kuchuk, N.V.Safryuk, V.F.Machulin, P.M.Lytvyn, V.G.Raicheva, A.E.Belyaev, Y.I.Mazur, E.A.DeCuir, M.E.Ware, M.O.Manasreh, G.J.Salamo: Journal of Physics D, 2011, 44[2], 025403