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3 February 2009 Reduced non-thermal roll-over in violet-emitting GaInN wide-well LEDs grown on low-dislocation-density substrates
Markus Maier; Thorsten Passow; Michael Kunzer; Wilhelm Schirmacher; Wilfried Pletschen; Lutz Kirste; Klaus Köhler; Joachim Wagner
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Proceedings Volume 7231, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIII; 72310K (2009) https://doi.org/10.1117/12.819404
Event: SPIE OPTO: Integrated Optoelectronic Devices, 2009, San Jose, California, United States
Abstract
Near-UV LEDs emitting at around 400 nm can be used e.g. as pump light source in tri-phosphor RGB white luminescence-conversion LEDs with high color rendering.1 Although non-thermal roll-over decreases towards shorter emission wavelengths in GaInN-based LEDs, this effect still limits the efficiency of 400 nm emitting LEDs at current densities above 50 A/cm2. One way to overcome non-thermal roll-over is to combine a GaInN wide-well active region with the growth on low dislocation density (DD) substrates. Single-well LEDs with GaInN layer widths between 3 nm and 18 nm were grown (a) directly on sapphire substrates with a resulting DD of 109 cm-2, (b) on low DD GaN templates on sapphire (DD of 108 cm-2), and (c) on freestanding GaN substrates (FS-GaN, DD of 4×107 cm-2). At low current densities (pulsed mode operation) the LEDs with a 3 nm GaInN QW active region showed the highest efficiency, irrespective of the substrate. However, the electroluminescence (EL) efficiency peaks at around 50 A/cm2 and shows a clear non-thermal roll-over towards higher current densities. The efficiency of LEDs with well widths >3 nm grown on sapphire decreases with increasing well width over the whole range of current densities (≤300 A/cm2). However, when grown on low DD GaN templates or FS-GaN, the efficiency of the LEDs with 11 and 18 nm wide GaInN layers surpasses that of the conventional LEDs (well widths ≤6 nm) for current densities ≥250 A/cm2, yielding the highest EL efficiency of all LED-structures.
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Markus Maier, Markus Maier, Thorsten Passow, Thorsten Passow, Michael Kunzer, Michael Kunzer, Wilhelm Schirmacher, Wilhelm Schirmacher, Wilfried Pletschen, Wilfried Pletschen, Lutz Kirste, Lutz Kirste, Klaus Köhler, Klaus Köhler, Joachim Wagner, Joachim Wagner, } "Reduced non-thermal roll-over in violet-emitting GaInN wide-well LEDs grown on low-dislocation-density substrates", Proc. SPIE 7231, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIII, 72310K (3 February 2009); doi: 10.1117/12.819404; https://doi.org/10.1117/12.819404
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