Observation of non-basal slip in semipolar In_xGa_1-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.