High-Efficiency InGaN-Based Yellow-Green Light-Emitting Diodes

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We demonstrate the characteristics of high-efficiency yellow-green InGaN-based light-emitting diodes (LEDs) with a strain-accommodative layer and textured surface. The LEDs have chip dimensions of $420\times 350$ μm2 and are packaged in the conventional lamp form. The peak wavelength, optical output power, luminaire efficiency, and external quantum efficiency are 560.7 nm, 0.926 mW, 7.8 lm/W, and 2.1%, respectively, at a driving current of 20 mA. In addition, the output power slope (mW/mA) is $3.3\times 10^{-2}$. It is found that there is potential to improve external quantum efficiency by introducing a chirp InGaN/GaN superlattice structure as the strain-accommodative layer and texturing the surface of the top P-layer in yellow-green InGaN/GaN LEDs. The low power slope can be attributed chiefly to the inferior crystalline quality due to unfavorable growth conditions of InGaN/GaN multiple quantum wells and partially to the stronger internal electric field due to the higher In composition in InGaN wells.
2010-02-25