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Proceedings Paper

Absorption in InGaN-on-sapphire LED structures: comparison between photocurrent measurement method (PMM) and photothermal deflection spectroscopy (PDS)
Author(s): Sven Silvius Schad; Barbara Neubert; Jens Bruening; Christoph Eichler; Frank Habel; Ferdinand Scholz; Peter Unger; Daniel Hofstetter
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Paper Abstract

In this work, we investigate the absorption distribution in InGaN-on-sapphire based light-emitting diodes (LEDs). We observed by photothermal deflection spectroscopy (PDS) and transmission measurements that most of the absorption takes place in a thin layer close to the sapphire substrate. The lateral intensity distribution in the surrounding of LED emitters is determined by the photocurrent measurement method. Based on the observations by PDS and transmission, a model for the lateral light propagation in the LED-wafer containing also a thin, strong absorbing layer is presented. It is shown that interference of the mode profiles with the absorbing layer leads to different modal absorption which explains the non-exponential intensity distribution. We are able to estimate the optical thickness of the absorbing layer to be 75 nm. Furthermore, this layer can be identified as one of the major loss mechanism in InGaN-LEDs grown on sapphire substrate due to the large absorption coefficient which is effective at the emission wavelength.

Paper Details

Date Published: 21 June 2004
PDF: 9 pages
Proc. SPIE 5366, Light-Emitting Diodes: Research, Manufacturing, and Applications VIII, (21 June 2004); doi: 10.1117/12.528783
Show Author Affiliations
Sven Silvius Schad, Univ. Ulm (Germany)
Barbara Neubert, Univ. Ulm (Germany)
Jens Bruening, Univ. Ulm (Germany)
Christoph Eichler, Univ. Ulm (Germany)
Frank Habel, Univ. Ulm (Germany)
Ferdinand Scholz, Univ. Ulm (Germany)
Peter Unger, Univ. Ulm (Germany)
Daniel Hofstetter, Univ. de Neuchatel (Switzerland)

Published in SPIE Proceedings Vol. 5366:
Light-Emitting Diodes: Research, Manufacturing, and Applications VIII
Steve A. Stockman; H. Walter Yao; E. Fred Schubert, Editor(s)

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