Deep ultraviolet emission from multiple quantum wells on flat N-polar AlN templates fabricated using periodical pulsed H 2 etching

Abstract In a previous study, we successfully grew flat N-polar AlN layers on a c -plane sapphire substrate with a misorientation angle of 2.0° by metal-organic vapor phase epitaxy. However, its surface had undulations due to step bunching, and therefore further improvement of the surface flatness is required. In this study, we employed pulsed H 2 etching during the growth of N-polar AlN layers to improve the surface flatness. Atomic force microscopy results indicated that the surface flatness was significantly improved, exhibiting a root mean square value of 0.4 nm. Further, the deep ultraviolet emission from AlGaN-based multiple quantum wells (MQWs) on the N-polar AlN layers was characterized, and the effect of the surface flatness on the optical characteristics was investigated. The surface flatness was found to play a crucial role in improving the optical characteristics of MQWs on N-polar AlN layers.