CONNECTING THE COMPOUND SEMICONDUCTOR COMMUNITY editorialview
October 2009
Volume 15 Number 7
Editor-in-Chief
David Ridsdale dr@angelbcl.co.uk
+44 (0)1923 690210
Consultant Editor
Richard Stevenson PhD
richardstevenson@angelbc.co.uk
+44 (0)1291 629640
Publisher
Jackie Cannon jc@angelbcl.co.uk
+44 (0)1923 690205
Account Handlers
Shehzad Munshi sm@angelbcl.co.uk
+44 (0)1923 690215
LED droop: controversy rages on
Tommy Beazley tb@angelbcl.co.uk
+44 (0)1923 690222
Design & Production Manager
Mitchell Gaynor mg@angelbcl.co.uk As I write this, many of our community are preparing for their trip to the eighth
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International Conference on Nitride Semiconductors (ICNS), which will be held
Circulation Director on the beautiful island of Jeju, off the south coast of Korea. If this meeting is
Jan Smoothy js@angelbcl.co.uk
+44 (0)1923 690200
anything like its predecessor in Las Vegas, it will be a
great affair. That gathering in the fall of 2007 had a
Subscriptions Manager
Debbie Higham dh@angelbcl.co.uk
tremendous buzz about it, and provided a fantastic
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showcase for leading academic work and triumphs in
Commercial Director industry. Let’s hope for more of the same.
Stephen Whitehurst stephen@angelbc.co.uk
+44 (0)2476 718970
LED droop was one of the topics discussed in Vegas.
Directors
Stephen Whitehurst, Jan Smoothy
At the start of that year Philips Lumileds claimed that it
Bill Dunlop Uprichard
had uncovered the mystery behind declining LED
Published by
output as the drive current is cranked up, and the
Angel Business Communications Ltd,
company selected this conference to reveal its finding.
Hannay House, 39 Clarendon Road,
Watford, Herts WD17 1JA, UK The culprit, according to Lumileds, was Auger
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F: +44 (0)1923 690201
recombination, a non-radiative interaction between an
electron, a hole, and a third carrier.
Angel Business Communications Ltd
Unit 6, Bow Court, Fletchworth Gate,
Burnsall Road, Coventry CV5 6SP
This talk and the subsequent paper have ignited a debate on LED droop that
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F: +44 (0)2476 718 971
rages on to this day. The debate’s central question is this: Auger, or not
Auger? Lumileds has an ally in Osram, which believes that the form of Auger
Compound Semiconductor is published eight times
a year on a controlled circulation basis.
recombination may involve interactions with defects or phonons. On the other
Non-qualifying individuals can subscribe at: side of the fence sits Fred Schubert and his co-workers from Rensselaer
£105.00/€158 pa (UK & Europe), £138.00 pa
(air mail), $198 pa (USA). Cover price £4.50.
Polytechnic Institute, who argue that electron leakage is to blame. Hadis
All information herein is believed to be correct at
Morkoç’s group at Virginia Commonwealth University are thinking along similar,
time of going to press. The publisher does not
accept responsibility for any errors and omissions.
but distinctly different lines, and point the finger at poor hole injection.
The views expressed in this publication are not
necessarily those of the publisher. Every effort has
been made to obtain copyright permission for the Other researchers are now joining the debate, including a Korean team that is
material contained in this publication.
arguing that Auger can’t be the cause. These researchers studied carrier rate
Angel Business Communications Ltd will be
equations, and thanks to some nifty mathematics, they reduce the number of
happy to acknowledge any copyright oversights
coefficients to fit the equation down to just one (see this month’s research
in a subsequent issue of the publication.
review for details). Curve fitting the data with their experimental measurements
Angel Business Communications Ltd
led them to conclude that Auger recombination only plays a very minor role in
© Copyright 2009. All rights reserved. Contents may
not be reproduced in whole or part without the the cause of droop.
written consent of the publishers. The paper used
within this magazine is produced by chain of
custody certified manufacturers, guaranteeing
Researchers joining the debate on the origin of LED droop should make for
sustainable sourcing.
fascinating discussion at ICNS. The nitrides continue to confuse us, but that’s
US mailing information: Compound Semiconductor
no bad thing – it makes this family of materials a great field for research.
(ISSN 1096-598X) is published 8 times a year
Jan/Feb, March, April/May, June, July,
August/September, October, November/December
Richard Stevenson PhD
for a subscription of $198 by Angel Business
Communications Ltd, Hannay House, Consultant Editor
39 Clarendon Road, Watford, Herts WD17 1JA, UK.
Periodicals postage paid at Rahway, NJ.
POSTMASTER: send address changes to: Compound
P.S. Last month I mentioned that USCB poached Hiroaki Ohta from Rohm.
Semiconductor, c/o Mercury International Ltd,
365 Blair Road, Avenel, NJ 07001
This is incorrect - he actually went from Rohm to Kyoto University, before
joining UCSB.
Printed by: Pensord Press.
ISSN 1096-598X
October 2009 www.compoundsemiconductor.net 3
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