High-power AlGaInN flip-chip light-emitting diodes

Data are presented on high-power AlGaInN flip-chip light-emitting diodes (FCLEDs). The FCLED is “flipped-over” or inverted compared to conventional AlGaInN light-emitting diodes (LEDs), and light is extracted through the transparent sapphire substrate. This avoids light absorption from the semitransparent metal contact in conventional epitaxial-up designs. The power FCLED has a large emitting area $(∼0.70 mm2)$ and an optimized contacting scheme allowing high current (200–1000 mA, $J∼30–143 A/cm2)$ operation with low forward voltages $(∼2.8 V$ at 200 mA), and therefore higher power conversion (“wall-plug”) efficiencies. The improved extraction efficiency of the FCLED provides 1.6 times more light compared to top-emitting power LEDs and ten times more light than conventional small-area $(∼0.07 mm2)$ LEDs. FCLEDs in the blue wavelength regime $(∼435 nm$ peak) exhibit $∼21%$ external quantum efficiency and $∼20%$ wall-plug efficiency at 200 mA and with record light output powers of 400 mW at 1.0 A.