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Near-UV to violet LEDs - wavelength dependence of efficiency limiting processes

Wellenlängenabhängigkeit der Effizienz-limitierenden Prozesse von UV-violett LEDs
: Kunzer, M.; Kaufmann, U.; Köhler, K.; Leancu, C.-C.; Liu, S.; Wagner, J.


Physica status solidi. C 4 (2007), No.7, pp.2822-2825
ISSN: 1610-1634
ISSN: 1610-1642
ISSN: 1862-6351
Journal Article
Fraunhofer IAF ()
UV LEDs; AlGaIN; piezo-effect; Piezoeffekt; quantum efficiency; Quanteneffizienz; current dependence; Strom-Abhängigkeit; GaN substrate; MOVPE

Two wavelength series (373-435 nm) of GaInN/GaN triple quantum well LED-structures, one on sapphire and one on GaN-templates, as well as a quantum well thickness series were grown by MOVPE. In order to study luminescence efficiency limiting effects the LED-structures were characterized by electroluminescence- and by temperature and excitation power dependent photoluminescence spectroscopy. The electroluminescence output and the internal quantum efficiency are peaked near 400 nm in both wavelength series, but output and efficiency are significantly enhanced for growth on templates. The photoluminescence data indicate that below 400 nm the efficiency, apart from insufficient vertical carrier confinement, is limited by poor localization within the quantum film plane while above 400 nm piezo-electric fields appear to be and important efficiency limiting effect.