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

2016; American Institute of Physics; Volume: 109; Issue: 19 Linguagem: Inglês

10.1063/1.4967501

1520-8842

Benjamin P. Yonkee, Erin C. Young, Steven P. DenBaars, Shuji Nakamura, James S. Speck,

Semiconductor materials and devices

A molecular beam epitaxy regrowth technique was demonstrated on standard industrial patterned sapphire substrate light-emitting diode (LED) epitaxial wafers emitting at 455 nm to form a GaN tunnel 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 with flip chip devices which utilize an LED floating in silicone over a BaSO4 coated header and produced a peak external quantum efficiency (EQE) of 78%. A high reflectivity mirror was designed using a seven-layer dielectric coating backed by aluminum which has a calculated angular averaged reflectivity over 98% between 400 and 500 nm. This was utilized to fabricate a flip chip LED which had a peak EQE and wall plug efficiency of 76% and 73%, respectively. This flip chip could increase light extraction over a traditional flip chip LED due to the increased reflectivity of the dielectric based mirror.