Observation of non-basal slip in semipolar InxGa1-xN/GaN heterostructures

In this paper, we report on observations of the operation of secondary slip systems to relieve lattice mismatch stress in semipolar InGaN/GaN heterostructures. Two-dimensional arrays of misfit dislocations were observed. Consistent with previous reports, primary relaxation occurred along the projected c direction via primary slip on the (0001) basal plane. In addition, evidence for secondary relaxation was detected in cathodoluminescence spectroscopy, high resolution x-ray diffraction, and transmission electron microscopy (TEM) studies. The secondary misfit dislocations were determined by TEM to have a-type Burgers vectors a/3 〈2¯110〉 and line directions along 〈42¯2¯3¯〉, consistent with prismatic slip on one of the m-type planes inclined with respect to the (112¯2) growth surface. Evidence of an additional slip system with approximate misfit line direction of type 〈202¯3¯〉 is also given.