10.6% external quantum efficiency germicidal UV LEDs grown on thin highly conductive n-AlGaN

Abstract

We report on the material challenges of the growth of highly conductive n-AlGaN in germicidal ultraviolet light emitting diodes (GUV LEDs), with the degradation of the surface morphology of thick highly doped n-AlGaN due to the Si anti-surfactant effect. Threading dislocation inclination, increasing relaxation, and eventual cracking were observed with epitaxial n-AlGaN films thicker than 400 nm, along with an increasing Ga composition with the same metalorganic flows. With the optimization of the n-AlGaN conductivity in previous works, thin n-AlGaN films with high conductivity along with a smoothing superlattice were incorporated in GUV LED devices, resulting in LEDs with 285 nm electroluminescence, a low forward voltage of 4.2 V with a peak external quantum efficiency (EQE) of 10.6% and a peak wall-plug efficiency of 8.6% below 1 A/cm2, and an EQE of 5.5% at 20 A/cm2.