• 42.55.Px;
  • 61.72.uj;
  • 81.15.Kk;
  • 85.60.Jb


Al0.25Ga0.75N films were grown on a grooved-Al0.25Ga0.75N/ AlN/sapphire template by MOVPE. The dislocation density on the grooved areas was as low as 1 × 108 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/cm2 at 7 °C. The characteristic temperature T0 was 174 K in the temperature range of 7–27 °C. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)