Spectral dependence of light extraction efficiency of high-power III-nitride light-emitting diodes

Using the recently suggested method of processing the data on external quantum efficiency as a function of output optical power, we have estimated the dependence of light extraction efficiency of high-power light-emitting diodes (LEDs) on their emission wavelength varied between 425 nm and 540 nm. The extraction efficiency is found to increase with the wavelength from similar to 80% to similar to 85% in this spectral range and to correlate with the wavelength dependence of reflectivity of the large-area p-electrode being the essential unit of the LED chip design. The correlation found identifies the incomplete reflection of emitted light from the electrode as the major mechanism eventually controlling the spectral dependence of the efficiency of light extraction from the LEDs. [GRAPHICS] Spectral dependence of light extraction efficiency of the UX: 3 (TM) LED chip: comparison of experiment and modelling results. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim