The microstructures of InGaN layers grown onto 2 different GaN substrates were studied: a standard GaN film on sapphire and an epitaxial lateral overgrown GaN structure. These two materials exhibit two distinct mechanisms of strain relaxation. InGaN epilayers on GaN were typically pseudomorphic and undergo elastic relaxation by the opening of threading dislocations into pyramidal pits. A different behavior occurred in the case of epitaxy on epitaxial lateral overgrown GaN where, in the absence of threading dislocations, slip occurred with the formation of periodic arrays of misfit dislocations. Potential slip systems responsible for this behavior were analyzed by using the Matthews-Blakeslee model and taking into account the Peierls forces. A comprehensive analysis of slip systems in the wurtzite structure was presented here and the role of threading dislocations in the strain relaxation of InGaN alloys was considered.

Slip Systems and Misfit Dislocations in InGaN Epilayers. S.Srinivasan, L.Geng, R.Liu, F.A.Ponce, Y.Narukawa, S.Tanaka Applied Physics Letters, 2003, 83[25], 5187-9