High-power AlGaInN flip-chip light-emitting diodes

Abstract

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 $\text{(∼0.70\hspace{0.05em}}{\mathrm{mm}}^{\mathrm{2}})$ and an optimized contacting scheme allowing high current (200–1000 mA, $\text{J∼30–143\hspace{0.05em}}{\mathrm{A/cm}}^{\mathrm{2}})$ operation with low forward voltages $\text{(∼2.8\hspace{0.05em}}\mathrm{V}$ 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 $\text{(∼0.07\hspace{0.05em}}{\mathrm{mm}}^{\mathrm{2}})$ LEDs. FCLEDs in the blue wavelength regime $\text{(∼435\hspace{0.05em}}\mathrm{nm}$ peak) exhibit $\text{∼21\%}$ external quantum efficiency and $\text{∼20\%}$ wall-plug efficiency at 200 mA and with record light output powers of 400 mW at 1.0 A.