Bright Deep Ultraviolet Luminescence from Semipolar AlGaN Multiple Quantum Wells Grown on Dislocation-Free Crystal Grains

High-quality AlGaN multiple quantum wells (MQWs) were fabricated successfully on semipolar facets of the crystal grains by metal-organic vapor phase epitaxy. Utilizing the advantage of epitaxial lateral overgrowth, dislocation-free can be achieved on the wing region of the crystal grain with semipolar facets. Distinct cathodoluminescence images were observed in the two semipolar MQWs. The step bunching facets contain a high density of macrosteps with Ga-rich ribbons that result in wire-like emission along the steps. By contrast, the flat semipolar MQWs present more uniform emission behaviours. Bright luminescence is observed from both dislocation-free semipolar MQWs. Compared to the regular c-plane planar MQWs, the emission from semipolar MQWs is 1.26 and 4.6 times higher at low and room temperature conditions, respectively. This work sheds new light on the development of high-performance semipolar AlGaN-based deep ultraviolet light-emitting diodes.