Improvement of Light Extraction Efficiency for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

AlGaN-based deep ultraviolet light-emitting diodes (LEDs) with aluminum reflective electrodes deposited to cover both p- and n-mesh contact electrodes have been fabricated. A 1.55-fold increase in light extraction efficiency has been demonstrated. Despite their reduced contact area, the LEDs exhibited only a slight increase in forward voltage of 0.45 V at 20 mA. Also, their 50% lifetime was estimated to be about 10,000 h at 20 mA DC at room temperature by extrapolation. Owing to the reflective electrodes, a 288 nm LED with external quantum efficiency as high as 5.4% was achieved. The light output power was 4.6 mW at 20 mA.