Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 53: GaN: Devices

HL 53.7: Talk

Wednesday, March 13, 2013, 11:30–11:45, H15

Investigation of extraction efficiency and internal quantum efficiency of GaN-based LEDs — •Ailun Zhao, Uwe Rossow, Heiko Bremers, and Andreas Hangleiter — Institut für Angewandte Physik, TU Braunschweig

In order to better understand the real physical mechanism of efficiency droop for GaN-based light emitting diodes (LEDs), it is very important to know the internal quantum efficiency under electroluminescence conditions since it plays a crucial role. In our study, we calculate the extraction efficiency of our LEDs and subsequently calibrated the results using a systematic variation of the LED structure. In our calculation we consider polarization-dependent partial reflections at interfaces as well as reflections at the metal contact and their interface. Both the dispersion of the refractive indices as well as the complex refraction index of the metal mirror are taken into account. We compare the result of the calculation with experimental data from a series of LEDs with varied distance between the quantum well and the mirror. This procedure allows us to obtain an absolute calibration of the extraction efficiency. Using the result for the extraction efficiency we have determined the internal efficiency from the measured efficiencies for LEDs with various modifications of the active region in order to assess their impact on the droop.