High‐performance UV emitter grown on high‐crystalline‐quality AlGaN underlying layer

Al 0.25 Ga 0.75 N films were grown on a grooved-Al 0.25 Ga 0.75 N/ AlN/sapphire template by MOVPE. The dislocation density on the grooved areas was as low as 1 x 10 8 cm ―2 . We fabricated a UVA light-emitting diode grown on such an AlGaN underlying layer exhibiting an output power of 12 mW at a DC current of 50 mA with a peak emission wavelength of 345 nm, which corresponds to an external quantum efficiency of 6.7%. This efficiency is the highest reported to date in this wavelength region. We also fabricated a 358 nm UVA laser diode (LD) using a GaN/AlGaN MQW active layer grown on an AlGaN underlying layer. This UV LD exhibits a threshold current of 73 mA and a corresponding current density of 3.8 kA/cm 2 at 7 °C. The characteristic temperature To was 174 K in the temperature range of 7―27 °C.