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Towards a deeper understanding of the reduced efficiency droop in low defect-density GaInN wide-well LEDs

: Maier, M.; Passow, T.; Kunzer, M.; Pletschen, W.; Köhler, K.; Wagner, J.


Physica status solidi. C 7 (2010), No.7-8, pp.2148-2150
ISSN: 1610-1634
ISSN: 1610-1642
ISSN: 1862-6351
International Conference on Nitride Semiconductors (ICNS) <8, 2009, Jeju/Korea>
Journal Article, Conference Paper
Fraunhofer IAF ()
InGaN/GaN; LED; efficiency droop; time resolved electroluminescence

A series of 400 nm emitting GaInN/GaN single-well light-emitting diodes, grown on ultra-low dislocation density GaN templates with well widths varying between 3 and 18 nm, were investigated by pulsed and time resolved electroluminescence measurements using small signal modulation technique for the latter. A reduction of the efficiency droop at high current densities with increasing well width was observed. The highest overall external quantum efficiency was obtained for LEDs with 11 nm thick double-heterostructure (or wide well) active region at current densities above 70 A/cm2. Furthermore, carrier lifetime and volume carrier density in the wells were determined. A model based on the interplay between defect assisted recombination, depending on dislocation density, and strongly carrier density dependent loss processes is presented explaining the well-thickness dependence of the efficiency droop.