Output Power Enhancement of Vertical-Injection Ultraviolet Light-Emitting Diodes by GaN-Free and Surface Roughness Structures

Nitride-based UV, vertical-injection light-emitting diodes (VLEDs) with GaN-free and surface roughness structures operating at 365 nm were proposed and demonstrated by a combination of wafer bonding and laser lift-off processes. The GaN-free structure offers a promising potential for enhancing the light output of UV-VLEDs. The 3.2x light output enhancement was performed by removing the GaN. With the help of adopting a roughened surface, the light-output power of the UV-VLEDs could be further enhanced by a factor of 2.3 as compared with that of UV-VLED without a roughened surface. The total enhancement of surface-roughened GaN-free UV-VLEDs was increased by a factor of 7.8 compared to that of conventional UV-LEDs at a driving current injection of 250 mA.