Enhanced performance of GaN-based vertical light-emitting diodes with circular protrusions surmounted by hexagonal cones and indium-zinc oxide current spreading layer

The performance of vertically structured GaN-based light-emitting diodes (VLEDs) with an efficient surface roughening scheme that uses KrF laser irradiation, chemical wet etching, and an indium-zinc oxide (IZO) transparent conductive layer atop the n-GaN surface is investigated. The GaN surface, with circular protrusions and hexagonal cones, gives photons multiple opportunities to find escape cones, and the IZO film acts as a current spreading layer. The fabricated VLEDs with the proposed surface roughening scheme exhibited 79.3 and 65.1% increases in light output power at 350 and 750 mA, respectively, and showed a relatively low forward voltage compared to that of regular VLEDs.