GaN/AlGaN multiple quantum wells on a-plane GaN pillars for stripe-geometry nonpolar ultraviolet light-emitting devices

We investigated the growth of ${\mathrm{GaN/Al}}_{\text{0.20}}{\mathrm{Ga}}_{\text{0.80}}\mathrm{N}$ multiple quantum wells (MQWs) on selective-area-grown a-plane GaN pillars over r-plane sapphire. In contrast to the MQWs grown on planar a-plane GaN templates, these ${\mathrm{GaN/Al}}_{\text{0.20}}{\mathrm{Ga}}_{\text{0.8}}\mathrm{N}$ MQWs on the pillars exhibited pit-free and atomically smooth surface morphology. Their structural quality and their UV emission (at 357 nm) increased with the underlying pillar height. The epitaxy of GaN/AlGaN MQWs on the selective-area-grown pillars is thus a promising and simple approach for fabricating stripe-geometry, high-efficiency, nonpolar UV emitters.