AlN base layers for UV LEDs - Couverture souple

Walde, Sebastian

 
9783736974517: AlN base layers for UV LEDs
Couverture souple
ISBN 10 : 3736974515 ISBN 13 : 9783736974517
Editeur : Cuvillier, 2021

Synopsis

To enable the fabrication of high performance ultraviolet (UV) light-emitting diodes (LEDs) this work aims at improving the quality of AlN base layers on sapphire substrates. The main issues for UV LEDs are still a limited internal quantum efficiency due to a high amount of threading dislocations along with a limited light extraction efficiency due to total internal reflection at the AlN/sapphire interface. Therefore, high-temperature annealing of AlN/sapphire layers and growth on nanopatterned sapphire substrates were comprehensively investigated. High-temperature annealing was applied to AlN layers of different strain and thickness grown by metalorganic vapour phase epitaxy (MOVPE). The threading dislocation density could be successfully reduced by more than one order of magnitude down to 6 × 108 cm-2. Wave optical simulations of UV LEDs on nanopatterned sapphire substrates (NPSS) were conducted and showed a potential increase in light extraction efficiency compared to a planar substrate. The optimized MOVPE growth process on sapphire nanopillars and sapphire nanoholes resulted in a fully coalesced and atomically smooth AlN surface. The threading dislocation density was reduced to 1 ×109 cm-2 for AlN on both nanopillars and nanoholes. UVC LEDs emitting at 265 nm wavelength were grown on top of the developed templates. Increased internal efficiency was obtained by reduced dislocation density and more efficient light extraction was achieved on NPSS in case of a transparent heterostructure and reflective contacts. Thus, the developed templates yield considerable improvement in light output compared to conventional templates.

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Éditeur
Cuvillier
Date d'édition
2021
Langue
anglais
ISBN 10 
3736974515
ISBN 13 
9783736974517
Reliure
Broché
Nombre de pages
156
Coordonnées du fabricant
info@cuvillier.de
info@cuvillier.de

Nonnenstieg 8
Göttingen
37075
Allemagne