Abstract
Luminescence efficiency droop has been studied in AlGaN epitaxial layers and multiple quantum wells (MQWs) with different strength of carrier localization in a wide range of temperatures. It is shown that the dominant mechanism leading to droop, i.e., the efficiency reduction at high carrier densities, is determined by the carrier thermalization conditions and the ratio between carrier thermal energy and localization depth. The droop mechanisms, such as the occupation-enhanced redistribution of nonthermalized carriers, the enhancement of nonradiative recombination due to carrier delocalization, and excitation-enhanced carrier transport to extended defects or stimulated emission, are discussed.
Highlights
Luminescence efficiency droop has been studied in AlGaN epitaxial layers and multiple quantum wells (MQWs) with different strength of carrier localization in a wide range of temperatures
It is shown that the dominant mechanism leading to droop, i.e., the efficiency reduction at high carrier densities, is determined by the carrier thermalization conditions and the ratio between carrier thermal energy and localization depth
III-nitride-based light-emitting diodes (LEDs) suffer from the efficiency droop effect: their quantum efficiency peaks at low driving currents and decreases significantly at higher currents, which are desired for high-power applications like general lighting
Summary
Luminescence efficiency droop has been studied in AlGaN epitaxial layers and multiple quantum wells (MQWs) with different strength of carrier localization in a wide range of temperatures. (Received 8 September 2015; accepted 14 April 2016; published online 21 April 2016)
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