Table Of ContentSolid State Luminescence
Solid State Luminescence
Theory, materials and devices
Edited by
A.R. Kitai
Department of Materials Science and Engineering and Engineering Physics
McMaster University, Ontario, Canada
I~nl SPR1NGER-SCIENCE+BUSINESS MEDIA, B.V.
PubIished by Cbapman & HalI, 2-6 Boundary Row, London SEI 8HN
Chapman & Hali, 2-6 Boundary Row, London SEI 8HN, UK
Blackie Academic & Professional, Wester Cleddens Road, Bishopbriggs,
Glasgow G64 2NZ, UK
Chapman & Hali Inc., 29 West 35th Street, New York NY1000l, USA
Chapman & Hali Japan, Thomson Publishing Japan, Hirakawacho Nemoto
Building,6F, 1-7-11 Hirakawa-cho, Chiyoda-ku, Tokyo 102, Japan
Chapman & Hali Australia, Thomas Nelson Australia, 102 Dodds Street,
South Melboume, Victoria 3205, Australia
Chapman & Hali India, R. Seshadri, 32 Second Main Road, CIT East,
Madras 600 035, India
First edition 1993
© 1993 Springer Science+Business Media Dordrecht
Originally published by Chapman & Hali in 1993
Softcover reprint of the hardcover 1 st edition 1993
Typeset in 10/12 Times by Interprint Limited, Malta
ISBN 978-94-010-4664-0 ISBN 978-94-011-1522-3 (eBook)
DOI 10.1007/978-94-011-1522-3
Apart from any fair dealing for the purposes of research or private study, or
criticism or review, as permitted under the UK Copyright Designs and
Patents Act, 1988, this publication may not be reproduced, stored, or
transmitted, in any form or by any means, without the prior permission in
writing of the publishers, or in the case of reprographic reproduction only in
accordance with the terms of the Iicences issued by the Copyright Licensing
Agency in the UK, or in accordance with the terms of Iicences issued by
the appropriate Reproduction Rights Organization outside the UK.
Enquiries conceming reproduction outside the terms stated here should be
sent to the publishers at the London address printed on this page.
The publisher makes no representation, express or implied, with regard to
the accuracy of the information contained in this book and cannot accept
any legal responsibility or Iiability for any errors or omissions that may be
made.
A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication data available.
@! Printed on permanent acid-free text paper, manufactured in accordance
with the proposed ANSIjNISO Z 39,48-199X and AN SI Z 39.48-1984
Contents
List of contributors Vll
Preface ix
Principles of luminescence 1
A.H. Kitai
2 Luminescent centres in insulators 21
G. Blasse
3 Luminescence spectroscopy 53
U. W. Pohl and H.-E. Gumlich
4 One-photon rare earth optical transitions: recent theoretical
developments 97
G. W. Burdick and M.e. Downer
5 Thin film electroluminescence 133
G.O. Muller
6 Powder electro luminescence 159
S.S. Chadha
7 Thin film electroluminescence devices 229
R Mach
8 Light emitting diodes: materials growth and properties 263
S.P. DenBaars
9 Atomic layer epitaxy of phosphor thin films 293
B.W Sanders
10 Lamp phosphors 313
T.E. Peters, RG. Pappalardo and RB. Hunt, Jr
11 Phosphors for other applications 349
G. Blasse
Index 373
v
Contributors
G. Blasse
Debye Research Institute
University of Utrecht
Utrecht
The Netherlands
G.W. Burdick
The University of Texas at Austin
Texas
USA
S.S. Chadha
School of Biological and Chemical Sciences
University of Greenwich
London
UK
S.P. DenBaars
Materials Department
University of California, Santa Barbara
California
USA
M.C. Downer
The University of Texas at Austin
Texas
USA
H.-E. Gumlich
Technical University of Berlin
Berlin
Germany
Vll
Vlll Contributors
R.B. Hunt, Jr
GTE Laboratories Inc., Danvers
Massach usetts
USA
A.K. Kitai
Departments of Materials Science and Engineering Physics
McMaster University, Hamilton
Ontario
Canada
R. Mach
Central Institute for Electron Physics
Berlin
Germany
G.O. Muller
Central Institute for Electron Physics
Berlin
Germany
R.G. Pappalardo
GTE Laboratories Inc., Danvers
Massachusetts
USA
T.E. Peters
GTE Laboratories Inc., Chelmsford
Massachusetts
USA
U.W. Pohl
Technical University of Berlin
Berlin
Germany
B.W. Sanders
Institute for Environmental Chemistry
National Research Council Canada, Ottawa
Ontario
Canada
Preface
Historically, black body radiation in the tungsten filament lamp was our
primary industrial means for producing 'artificial' light, as it replaced gas
lamps. Solid state luminescent devices for applications ranging from lamps
to displays have proliferated since then, particularly owing to the develop-
ment of semiconductors and phosphors. Our lighting products are now
mostly phosphor based and this 'cold light' is replacing an increasing
fraction of tungsten filament lamps. Even light emitting diodes now chal-
lenge such lamps for automotive brake lights.
In the area of information displays, cathode ray tube phosphors have
proved themselves to be outstandingly efficient light emitters with excellent
colour capability. The current push for flat panel displays is quite intense,
and much confusion exists as to where development and commercialization
will occur most rapidly, but with the need for colour, it is now apparent that
solid state luminescence will play a primary role, as gas phase plasma
displays do not conveniently permit colour at the high resolution needed
today. The long term challenge to develop electroluminescent displays
continues, and high performance fluorescent lamps currently illuminate
liquid crystal monochrome and colour displays. The development of tri-
component rare earth phosphors is of particular importance.
This book begins with a chapter on the physics of luminescence, covering
the classical and quantum mechanical theory of radiation in atoms and
solids. Chapter 2 focuses on phosphors, describing the fundamental pro-
cesses and models that are useful to sort out the rather complex electronic
and vibrational interactions. Chapter 3 deals with state of the art experimen-
tal methods and gives examples of fundamental luminescence processes in
solids. Chapter 4 presents a current understanding of rare earth ions in
crystalline fields.
The next section of the book focuses on different device and material
types: thin film electroluminescence is described from a physics perspective
in Chapter 5 and Chapter 6 traces the rather painful but important
development of powder phosphors for electroluminescence.
IX
x Preface
Chapter 7 presents the current state of thin film electroluminescence, and
Chapter 8 is devoted to both the theory and technology involved in light
emitting diodes which are now reaching new levels of efficiency.
Chapter 9 discusses, in some detail, the concept of kinetically limited
growth for thin films which allows large area, uniform coverage of both
phosphor and semiconductor materials.
Finally Chapters 10 and 11 present a very comprehensive account of
phosphors for fluorescent lamps and special applications in for example,
medicine.
A.H. Kitai
Ontario
Canada
1
Principles of luminescence
A.H. Kitai
1.1 INTRODUCTION
Technologically important forms of luminescence may be broken into
several categories, as shown in Table 1.1. Although the means by which the
luminescence is excited varies, all luminescence is generated by means of
accelerating charges. The portion of the electromagnetic spectrum visible to
the human eye has wavelengths from 400 to 700 nm. The evolution of the
relatively narrow sensitivity range of the human eye is a complex subject,
but is intimately related to the solar spectrum, the absorbing behaviour of
the terrestrial atmosphere, and the reflecting properties of organic materials,
green being the dominant colour in nature and, not surprisingly, the
wavelength at which the human eye is most sensitive. In this chapter, we
cover the physical basis for radiation and radiation sources in solids that
produce visible light.
Table 1.1 Luminescence types, applications and typical efficiencies (visible output
power/electrical input power)
Luminescence type Typical application Luminous efficiency
Blackbody radiation Tungsten filament lamp -5%
Photoluminescence Fluorescent lamp -20%
Cathodoluminescence Television screen -10%
Electrol uminescence Light-emitting diode, 0.1-50%
flat panel display
1.2 RADIATION THEORY
A stationary point charge has an associated electric field E as shown in Fig.
1.1. A charge moving with uniform velocity relative to the observer gives
rise to a magnetic field as shown in Fig. 1.2.
1
2 Principles of luminescence
Fig. 1.1 The lines of electric field E due to a point charge q.
B
Fig. 1.2 The lines of magnetic field B due to a point charge q moving into the page
with uniform velocity.
Both electric and magnetic fields store energy; the total energy density is
given by
It is important to note that the energy density moves with the charge so long
as the charge is either stationary or undergoing uniform motion; this is
evident since a new reference frame may be constructed in which the
observer is stationary with respect to the charge.
For an accelerated charge, however, energy continuously leaves the
charge to compensate exactly the work done in causing the charge to
accelerate. Consider the charge q in Fig. 1.3. Initially at rest in position A,
it accelerates to position B and then stops there. The electric field lines now
emanate from position B, but would, further out, have emanated from
position A, since the field lines cannot convey information about the
location of the charge at speeds greater than the velocity of light c. This
results in kinks in the lines of electric field which propagate away from q
with velocity c. Each time q accelerates, a new series of propagating kinks
is generated. Each kink is made up of a component of E that is transverse
to the direction of expansion, which we call E 1-' If the velocity of the charge
during its acceleration does not exceed a small fraction of c, then for r large,
qa . ()
E1- = 2 sm
4n8oc r
