Fabrication of High Power Deep Ultraviolet Light-Emitting Diodes with Glass Lenses Using Atomic Diffusion Bonding

This work demonstrated that both the output power and external quantum efficiency of AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) are greatly enhanced by bonding glass lenses to the LED chips using atomic diffusion bonding (ADB). ADB is advantageous because it permits the bonding of glass to DUV-LEDs at room temperature. A Ti film was found to improve light transmittance through the bonding interface and to provide good bonding strength. In addition, hydrophilic treatment of the bonding surfaces prior to Ti film deposition during ADB and post-bonding annealing further enhanced the bonding strength. In this manner, 255 nm DUV-LEDs with glass lenses having n values almost equal to that of sapphire were fabricated, using the ADB process in conjunction with a 0.4-nm-thick Ti film on each side. Even though the glass lens exhibited some light absorption, the output power and the maximum external quantum efficiency of these glass-lens-bonded LEDs were both 2.5 times greater than the values for an LED without a lens. (C) The Author(s) 2019. Published by ECS.