Silver free III-nitride flip chip light-emitting-diode with wall plug efficiency over 70% utilizing a GaN tunnel junction

Amolecular beam epitaxy regrowth technique was demonstrated on standard industrial patterned sapphire substratelight-emitting diode(LED) epitaxial wafers emitting at 455  nm to form a GaNtunnel junction. By using an HF pretreatment on the wafers before regrowth, a voltage of 3.08  V at 20 A/cm2 was achieved on small area devices. A high extraction package was developed for comparison withflip chip devices which utilize anLED floating in silicone over a BaSO4coated header and produced a peak external quantum efficiency (EQE) of 78%. A highreflectivitymirror was designed using a seven-layerdielectriccoating backed byaluminum which has a calculated angular averagedreflectivity over 98% between 400 and 500  nm. This was utilized to fabricate aflip chipLED which had a peak EQE and wall plug efficiency of 76% and 73%, respectively. Thisflip chip could increase light extraction over a traditionalflip chipLED due to the increasedreflectivity of thedielectric basedmirror.

Source: Applied Physics Letters - November 9, 2016 Category: Physics Authors: B. P. Yonkee, E. C. Young, S. P. DenBaars, S. Nakamura and J. S. Speck Source Type: research