A pathway to strain-free AlGaN grown on native GaN substrates

We demonstrate that facet-controlled epitaxial lateral overgrowth enables the formation of regular, strain-relieving misfit dislocation (MD) arrays at {11−22} interfaces and results in relaxed growth of AlGaN on native GaN substrates (threading dislocation density <104 cm−2). Complementary plan-view and cross-sectional transmission electron microscopy studies confirmed the presence of uniform MD arrays with spacing matching the value predicted for an ideal, strain-relieving array. The MDs exhibited a pure edge-type Burgers vector (b = 1/3 ⟨11−20⟩) and were aligned parallel to [1−100]. Based on these results, we outline a pathway to achieve low threading dislocation densities in thick, relaxed, crack-free AlGaN epilayers grown on native GaN.