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Proceedings Paper

Position-controlled MOVPE growth and electro-optical characterization of core-shell InGaN/GaN microrod LEDs
Author(s): Tilman Schimpke; H.-J. Lugauer; A. Avramescu; T. Varghese; A. Koller; J. Hartmann; J. Ledig; A. Waag; M. Strassburg
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Paper Abstract

Today’s InGaN-based white LEDs still suffer from a significant efficiency reduction at elevated current densities, the so-called “Droop”. Core-shell microrods, with quantum wells (QWs) covering their entire surface, enable a tremendous increase in active area scaling with the rod’s aspect ratio. Enlarging the active area on a given footprint area is a viable and cost effective route to mitigate the droop by effectively reducing the local current density. Microrods were grown in a large volume metal-organic vapor phase epitaxy (MOVPE) reactor on GaN-on-sapphire substrates with a thin, patterned SiO2 mask for position control. Out of the mask openings, pencil-shaped n-doped GaN microrod cores were grown under conditions favoring 3D growth. In a second growth step, these cores are covered with a shell containing a quantum well and a p-n junction to form LED structures. The emission from the QWs on the different facets was studied using resonant temperature-dependent photoluminescence (PL) and cathodoluminescence (CL) measurements. The crystal quality of the structures was investigated by transmission electron microscopy (TEM) showing the absence of extended defects like threading dislocations in the 3D core. In order to fabricate LED chips, dedicated processes were developed to accommodate for the special requirements of the 3D geometry. The electrical and optical properties of ensembles of tens of thousands microrods connected in parallel are discussed.

Paper Details

Date Published: 8 March 2016
PDF: 8 pages
Proc. SPIE 9768, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XX, 97680T (8 March 2016); doi: 10.1117/12.2214122
Show Author Affiliations
Tilman Schimpke, OSRAM Opto Semiconductors GmbH (Germany)
Technische Univ. Braunschweig (Germany)
H.-J. Lugauer, OSRAM Opto Semiconductors GmbH (Germany)
A. Avramescu, OSRAM Opto Semiconductors GmbH (Germany)
T. Varghese, OSRAM Opto Semiconductors GmbH (Germany)
A. Koller, OSRAM Opto Semiconductors GmbH (Germany)
J. Hartmann, Technische Univ. Braunschweig (Germany)
J. Ledig, Technische Univ. Braunschweig (Germany)
A. Waag, Technische Univ. Braunschweig (Germany)
M. Strassburg, OSRAM Opto Semiconductors GmbH (Germany)

Published in SPIE Proceedings Vol. 9768:
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XX
Heonsu Jeon; Li-Wei Tu; Michael R. Krames; Martin Strassburg, Editor(s)

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