Generation of misfit dislocations by basal-plane slip in InGaN/GaN heterostructures

The authors have observed that for In_xGa_1-xN epitaxial layers grown on bulk GaN substrates exhibit slip on the basal plane, when in the presence of free surfaces that intercept the heterointerface and for indium compositions x≥0.07. This leads to almost complete relaxation of the local misfit strain by generation of radial-shape dislocation half loops. For x≥0.17, generation of straight misfit dislocations by glide on the secondary <1123> {1122} slip system is observed, in addition to the radial-shape half loops at surface pits. These two mechanisms act independently with no observed interaction between them, leading to the conclusion that slip on the basal plane occurs first during the growth process. The secondary slip system is activated later and involves a significantly higher critical stress energy.