III-nitride photonic-crystal light-emitting diodes with high extraction efficiency

Light-emitting diodes are becoming an increasingly attractive alternative to conventional light sources due to their small size, high efficiency and long lifetime. Ongoing research is dedicated to improving their performance through the use of more efficient light-generating and light-extracting structures. Here, we demonstrate light-emitting diodes achieving high extraction efficiency by using photonic crystals. The structures are III-nitride thin-film light-emitting diodes emitting at lambda=450 nm. The photonic-crystal layer provides superior optical mode control compared to conventional III-nitride light-emitting diodes, efficiently coupling guided modes out of the light-emitting diode. Fabry-Perot and photonic-crystal induced modes are observed in the far-field radiation patterns and are matched to theoretical electromagnetic calculations. The optical mode control results in a high-performance light-emitting diode with an estimated unencapsulated light extraction of similar to 73%, higher than any unencapsulated III-nitride light-emitting diode measured to date.