Light output improvement of GaN-based light-emitting diodes grown on Si (111) by a via-thin-film structure

This work reports the fabrication of via-thin-film light-emitting diode （via-TF-LED） to improve the light output power （LOP） of blue/white GaN-based LEDs grown on Si （111） substrates. The as-fabricated via-TF-LEDs were featured with a roughened n-GaN surface and the p-GaN surface bonded to a wafer carrier with a silver-based reflective electrode, together with an array of embedded n-type via pillar metal contact from the p-GaN surface etched through the multiple-quantum-wells （MQWs） into the n-GaN layer. When operated at 350 mA, the via-TF- LED gave an enhanced blue LOP by 7.8% and over 3.5 times as compared to the vertical thin-film LED （TF-LED） and the conventional lateral structure LED （LS-LED）. After covering with yellow phosphor that converts some blue photons into yellow light, the via-TF-LED emitted an enhanced white luminous flux by 13.5% and over 5 times, as compared with the white TF-LED and the white LS-LED, respectively. The significant LOP improve- ment of the via-TF-LED was attributed to the elimination of light absorption by the Si （111） epitaxial substrate and the finger-like n-electrodes on the roughened emitting surface.