AlGaN -based 280nm light-emitting diodes with continuous wave powers in excess of 1.5mW

We report on AlGaN-based light-emitting diodes over sapphire with peak emission at 280nm. A modified active layer structure consisting of four multiple quantum wells, addition of an electron blocking magnesium doped p-AlGaN layer, improved contacts along with flip-chip packaging resulted in a cw power of 0.7mW at 230mA for a single 200μm×200μm device. Flip-chipping four 100μm×100μm devices in a parallel configuration improved the dc saturation current and enabled us to obtain a cw power of 1.53mW (at 450mA) and a pulse power as high as 24mW (at 1.5A). These powers translate to values of 0.36% and 0.12% for the external quantum efficiency and the wall plug efficiency.