Journal of the Korean Physical Society

pISSN 0374-4884 eISSN 1976-8524


Condensed Matter

J. Korean Phy. Soc. 2011; 58(3): 503-508

Published online March 15, 2011

Copyright © The Korean Physical Society.

An Explanation of Efficiency Droop in InGaN-based Light Emitting Diodes: Saturated Radiative Recombination Rate at Randomly Distributed In-Rich Active Areas

Jong-In Shim, Hyungsung Kim, Dong-Soo Shin, Han-Youl Yoo


We present a comprehensive model of the dependence of the internal quantum efficiency (IQE) on both the temperature and the carrier density in InGaN-based blue and green light emitting diodes (LEDs). In our model, carriers are dominantly located and recombine both radiatively and nonradiatively inside randomly distributed In-rich areas of the InGaN quantum wells (QWs). In those areas, the carrier density is very high even at a small current density. We propose that the saturated radiative recombination rate is a primary factor determining the IQE droop of InGaNbased LEDs. In typical InGaN-based QWs, it is common for the total carrier recombination rate to be smaller than the carrier injection rate even at a small current density. This is mostly attributable to the saturation of the radiative recombination rate. The saturation of the radiative recombination rate increases carrier density in InGaN QWs, enlarges nonradiative carrier losses, and eventually gives rise to the large IQE droop with increasing current. We show how the radiative recombination rate saturates and the radiative recombination rate has influence on the IQE droop in InGaN-based QW LEDs.

Keywords: Radiative recombination rate, In-rich area, Internal quantum efficiency, Efficiency droop, Light emitting diode