Enhancement in external quantum efficiency of 365 nm vertical-type ultraviolet light-emitting diodes with embedded oxide structure

High performance 365 nm vertical-type ultraviolet light-emitting diodes (UV-LEDs) were developed using an embedded self-textured oxide (STO) structure using metal-organic chemical vapor deposition system. From etch-pit-density results, the dislocation densities of LED epilayers were effectively reduced to 5.6×106 cm-2 by inserting the STO structures due to the relaxation of residual stress. The vertical-type UV-LEDs are fabricated using a combination technique of metal bonding and sapphire substrate separation. When the UV-LEDs (size: 45 × 45 mil2) were driven with a 20 mA injection current, the output powers of the LEDs with and without STO were measured to be 10.2 and 5.51 mW, respectively. The external quantum efficiency of LEDs with STO exhibits 32% higher than that of LED without STO. As increasing injection current to 350 mA, a near 45 mW light output was measured from STO-LED sample. This benefit was attributed to the introduction of STO structure which can not only block the propagation of threading dislocations but also intensify the light extraction of LED.