Single peak deep ultraviolet emission and high internal quantum efficiency in AlGaN quantum wells grown on large miscut sapphire substrates

Abstract

Deep ultraviolet (DUV) AlxGa1-xN/AlyGa1-yN-based multiple quantum wells (MQWs) were grown on sapphire substrates with miscut angles of 0.2° and 4°. Significantly reduced edge type dislocation density and in-plane anisotropy of dislocation distributions were demonstrated for MQWs grown on high miscut sapphire substrate. Up to 10-fold enhanced MQW emission was observed for MQWs grown on 4° miscut sapphire compared to that grown on 0.2° miscut sapphire, and internal quantum efficiency (IQE) as large as 88% was achieved. Compositional inhomogeneity and thus formation of potential minimum were ambiguously demonstrated by localized cathodoluminescence spectra across the step bunched surface of the MQW sample. However, from the macroscale point of view, single peak PL luminescence was shown for MQW grown on high miscut sapphire without peak separation, suggesting a strongly carrier localization effect. A three-dimensional atom diffusion and desorption model describing the MQW growth was also proposed. This work provides a promising approach towards the realization of highly-efficient DUV emitters.