AN INTERDISCIPLINARY JOURNAL OF
`D~=~t:ARCH ON EXCITED STATE PROCESSES
`IN CONDENSED MATTER
`
`VOLUMES 110&61
`APRIL 1994
`JLUMA 60&61 1-1030 (1994)
`To be followed by Vol. 69.4
`
`ISSN 0022-231~
`
`Proceedings of the 1993
`INTERNATIONAL CONFERENCE
`ON LUMINESCENCE
`
`THE
`UNIVERSITY OF
`CONNECTICUT
`
`~ ;::)
`
`......
`0
`::::::..
`1.1..1
`......
`t· ~
`0
`Q
`
`\
`
`'•
`
`LL
`0
`_.J
`<( z
`a:
`::::)
`0
`J
`
`Vizio EX1025 Page 0001
`
`

`

`JOURNAL OF
`LUMINESCENCE
`
`AN INTERDISCIPLINARY JOURNAL OF
`
`RESEARCH ON EXCITED STATE PROCESSES
`
`IN CONDENSED MATTER
`
`EDITOR
`
`R.S. MELTZER
`
`Department of Physics and Astronomy
`The University of Georgia
`
`VOLUMES 60 & 61 (1994)
`
`ELSEVIER
`
`Vizio EX1025 Page 0002
`
`

`

`Contents
`
`Preface ......... .... . ......................... .... . ....................... . .. .
`
`Committees
`
`Contents .. . ...... ... .. ........ .. ..... .. ... ..... . . ... ......................... .
`
`xi
`
`vii
`
`ix
`
`XI
`
`Announcement of the ICL '93 prize recipient. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`xxvii
`
`Section 1. Bulk semiconductors
`
`Two-photon spectroscopy of lS-excitons in an AC electric field
`G. Biese, D. Frohlich, W. Nieswand, E. Mohler ............ ......................... .
`
`Fluorescent decay times of excitons bound to oxygen traps in ZnTe:O
`Y. Burki, W. Czaja, V. Capozzi, P. Schwendimann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Photoluminescence spectra of trivalent praseodymium implanted in semi-insulating GaAs
`L.E. Erickson, U. Akano, I. Mitchell, N. Rowell, A. Wang . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Optical gain in ZnTe/GaAs epitaxial layers grown by MOVPE
`F.A. Majumder, H. Kalt, C. Klingshirn, A. Naumov, H. Stanzl, W. Gebhardt. . . . . . . . . . . . . . .
`
`Spectroscopic detection of the V + ( d 4
`) acceptor state in zinc selenide and zinc sulfide
`G. Goetz, U.W. Pohl, H.-1. Schulz, M. Thiede . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Excited-state absorption of ZnSe doped with cobalt
`A. Ehlert, 1. Dreyhsig, H .-E. Gumlich, 1.W. Allen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Exciton- phonon interaction and energy transfer of nitrogen-bound excitons in GaP
`T. Bouma, A.1. Scholten, H.A. Zondag, Tj. Luijendijk, 1.1. Dijkhuis . . . . . . . . . . . . . . . . . . . . . .
`
`Donor- acceptor pair decay and evaluation of the recombination constant and the Bohr radii of
`shallow impurities in ZnSe
`G.-1. Yi, G.F. Neumark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Optically stimulated fluorescent emission in Ca 1 - xSrxS:Ce
`D. Maneval, B. Ray, I.V.F. Viney, J.W. Brightwell, B.W. Arterton. . . . . . . . . . . . . . . . . . . . . . . .
`
`Specular optical activity and specular gyrotropic linear dichroism in semiconductors
`A.R. Bungay, Y. Pointel, N.I. Zheludev . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Microwave modulated and thermal modulated photoluminescence studies of Pbl 2 layered semi(cid:173)
`conductor
`E. Lifshitz, L. Bykov, B.M. Ashkinadze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`Fine structure of zero-phonon lines in polymorphic ZnS:Fe 2 +
`B. Litzenburger, U.W. Pohl, H.-E. Gumlich. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4
`
`8
`
`12
`
`16
`
`21
`
`26
`
`29
`
`32
`
`36
`
`40
`
`44
`
`Vizio EX1025 Page 0003
`
`

`

`i
`
`ELSEVIER
`
`Journal of Luminescence 60&61 (1 994) 127- 130
`
`JOURNAL OF
`
`LUMINESCENCE
`
`Cathodoluminescence of Ce: La2 Be 20 5 single crystals
`D. M. Gualtieri
`Applied Physics Laboratory , Allied Signal Research and Technology, P.O. Box 1021, Morristown, NJ 07962-1021, USA
`
`Abstract
`
`Ce 3 + : Y 3Al 50 12 (Ce: YAG) is an important phosphor in high intensity CRT displays since it does not saturate at high
`electron beam power. The saturation power level is of the order of 1 W j cm 2 for most cathodoluminescent materials, and
`this limits the maximum surface brightness of a typical cathode ray tube. However, Ce 3 + : Y AG has been found to be
`linear to at least 104 WI em 2
`. This performance has encouraged our examination of another cerium activated phosphor,
`lanthanum beryllate, Ce: La 2Be 20 5 (Ce: BEL). A crystal of lanthanum beryllate activated with a cerium concentration of
`410 1 8
`atoms/ cm 3 was grown by the Czochralski crystal growth technique. Wafers were prepared from the crystal and
`analyzed in both the as-grown state and after annealing in a flowing atmosphere of 10% by volume hydrogen in argon at
`1150 oc for 4 h. Cathodoluminescent measurements revealed a broadband blue emission of 100 nm width centered at
`480 nm, a blue-shifted analog of the Ce: YAG spectrum. A linear efficiency of0.13lm / W was found to a power loading of
`8 W/ cm 2
`. Pulsed excitation of aCe: BEL crystal by 375 nm radiation produced by frequency doubling of a 750nm laser
`demonstrated a decay time of the fluorescence of the order of 50 ns. All these data show that Ce: La2 Be 20 5 is an excellent
`candidate as a blue phosphor for high intensity CRT applications, particularly for high resolution projection displays
`using single crystal faceplates.
`
`1. Introduction
`
`Conventional CRT faceplates are formed by the
`deposition of phosphor powder on the inside of
`a glass envelope of limited thermal conductivity.
`The image resolution and power capabilities of
`these faceplates are limited, and many applications
`now require CRT performance at the limits of
`phosphor facepl ate technology. The resolution of
`conventional faceplates is limited by phosphor par(cid:173)
`ticle size to about 20 J..lm. Long-term operation
`at high intensity is limited by a decomposition
`threshold of about 1 W j cm 2
`. Short-term operation
`at high intensity is limited by saturation effects
`which, aside from thermal quenching and space
`charge build-up, arise from activator ground
`state depletion, excited stated absorption and
`
`cross-relaxation processes. Activator ground state
`depletion as a consequence of long fluorescent
`decay time is a general feature of phosphors [1].
`Phosphor particles will actually melt at about
`5 W j cm 2
`• High-intensity operation also
`limits
`phosphor lifetime by a process called coulombic
`degradation. This failure mode reduces the inten(cid:173)
`sity of P53, a standard phosphor, to 50o/o of
`its
`initial value after an electron dosage of
`140 C/ em 2
`. This leads to a CRT lifetime in a high
`luminance application of about 1000 h under the
`best conditions.
`Single crystal cathode ray tube faceplates have
`several significant advantages over powder phos(cid:173)
`phor faceplates. Since single crystals have no
`granulation, resolution is
`limited only by the
`dimension of the electron beam. Single crystal
`
`0022-2313/94/$07.00 © 1994 - Elsevier Science B.V. All rights reserved
`SSD1 002 2-23 1 3 (93) E0289- A
`
`Vizio EX1025 Page 0004
`
`

`

`128
`
`D.M. Gualtieri / Journal of Luminescence 60&61 ( 1994) 127- 130
`
`phosphor faceplates do not decompose at high
`power levels, and, because of the intimate thermal
`contact between the excited phosphor portion of
`the crystal and the rest of the crystal faceplate,
`thermal quenching effects are mitigated. Single
`crystal phosphors have shown no coulombic degra(cid:173)
`dation.
`Since the saturation power level is of the order
`of one watt per square centimeter for most
`cathodoluminescent materials,
`this
`limits
`the
`maximum surface brightness of the face of a
`typical cathode ray tube [2,3]. The single crystal
`phosphor, cerium activated yttrium aluminum
`garnet, Ce 3 + :Y 3 Al 50 12 or Ce:YAG, is a cath(cid:173)
`odoluminescent material which has not been
`found to saturate to an excitation power level
`of 104 W j cm 2 [3,4]. The color of the emitted light
`from Ce: YAG
`is yellow-green, and
`its cath(cid:173)
`odoluminescent spectrum
`is sufficiently broad
`that both green and red colors are available
`through filtering, but there is practically no light
`emission in the blue region of wavelength less
`than 475 nm. Red-shifting of the cerium spectrum
`by nearly 50 nm has been accomplished by substi(cid:173)
`tution of gadolinium for yttrium, but similar
`attempts at blue-shifting have been only partially
`successful
`[5]. Single crystal cerium-activated
`yttrium orthosilicate, Ce: Y 2Si0 5 or Ce: YSO,
`a blue phosphor, has been investigated by AT&T
`Bell Laboratories [6,7] which found saturation at
`high power.
`The performance of Ce: Y AG has encouraged
`our examination of another cerium activated
`phosphor,
`lanthanum beryllate, Ce: La2 Be 2 0 5
`(Ce : BEL). BEL is a c-centered monoclinic crystal
`with lattice constants a = 0.7536, b = 0.7348 and
`c = 0.7439 nm and f3 = 91.55° [8]. Each unit cell
`contains four La 2Be 20 5 formula units, and a dis(cid:173)
`tinctive feature of the crystal structure is that
`the lanthanum cations, and the cerium activator
`cations which substitute
`for
`lanthanum, are
`irregularly coordinated to ten oxygen atoms. The
`density of lanthanum cations is 1.941022
`em - 3 ,
`and the refractive indices at a wavelength of
`1 ~mare nx = 1.9641 , ny = 1.9974, and nz = 2.0348.
`BEL has a melting point of a bout 1360 °C,
`and a thermal conductivity about half that of
`YAG.
`
`2. Material preparation
`
`A crystal of cerium activated lanthanum beryl(cid:173)
`late was grown by the Czochralski crystal growth
`technique from a heated mixture of cerium oxide,
`lanthanum oxide, and beryllium oxide
`in an
`iridium crucible at 1360oc [9]. The charge consis(cid:173)
`ted of a 330 g total mixture in the following molar
`percentages: La 20 3 , 49.75°/o; Ce 20 3 , 0.25°/o; BeO,
`50.00°/ o. This is an effective cerium doping of 0.5°/o
`in the melt. Care was taken to correct the weights of
`these oxide powders for absorbed water. This mix(cid:173)
`ture was fused in a cylindrical iridium crucible of
`370 g weight, 2 in (50 mm) in diameter, 2 in (50 mm)
`in height, using RF heating, and after homogeniz(cid:173)
`ing the mixture at a temperature somewhat above
`1400 °C, it was cooled to a temperature at which
`a growth of crystal was observed on the end of
`a seed crystal of b-axis BEL dipped into the molten
`mixture. A large single crystal, attached to the seed
`crystal, was
`then pulled from
`the melt with
`45 rev / min rotation at a rate of 0.5 mm/ h in a pro(cid:173)
`grammed furnace power cycle which was designed
`to give a cylindrical crystal shape. After sufficient
`crystal length had been achieved, the crystal was
`removed from the melt and slowly cooled. The
`resultant, approximately cylindrical, crystal of ce(cid:173)
`rium-doped lanthanum beryllate was 163.5 g in
`weight, 17/4in (108mm) long and 3/4in (19mm) in
`diameter.
`Mass spectrometric analysis of this crystal
`showed that the concentration of cerium sub(cid:173)
`stituted for lanthanum was 410 18
`atomsjcc. Wa(cid:173)
`fers 19 mm diameter by 3 mm thickness were pre(cid:173)
`pared from this crystal and some were annealed in
`a flowing atmosphere of 10°/o by volume hydrogen
`in argon at 1150 oc for 4 h. It was found that this
`reduction anneal changed the appearance of the
`crystal wafers from an orange color to transparent.
`The reduction anneal also doubled the cathodo(cid:173)
`luminescent efficiency of the Ce: BEL wafers.
`
`3. Photometry
`
`Wafers were coated on one side with 80 nm of
`aluminum and mounted in a demountable face(cid:173)
`plate cathode ray tube testing station. The wafers
`
`Vizio EX1025 Page 0005
`
`

`

`D.M. Gualtieri / Journal of Luminescence 60&61 ( 1994) 127- 130
`
`129
`
`~
`0
`8
`0
`
`100
`
`60
`
`2
`~ 80
`<1>
`a_
`0
`c
`<1>
`~
`<1>
`e:..
`.?;- 40
`·u:;
`c:
`.$
`.E 20
`
`0
`
`0
`0
`
`0
`0
`
`00
`
`00
`0
`
`~
`
`Ce:BEL
`15 kV
`
`<iiJ
`0
`
`'b
`
`0
`0
`0
`'6
`0
`0
`0
`'0
`0
`'0
`
`(J)
`0
`
`o~Trrh~rh~~rM~~~~~
`350
`400 450 500
`550 600
`650
`Wavelength (nm)
`
`Fig. 1. Cathodoluminescent spectrum for Ce: BEL
`
`0.16-.----- - - - - - - - - - - - ,
`Ce:BEL
`
`0.14
`
`<1>
`
`~0.12
`~ c: 0.1
`E 2. 0.08
`>. g 0.06
`~ 0.04
`w
`
`<1>
`
`Ce:YSO
`
`0.02
`
`o,rr .. -.rT.-~'I!rT'~'I~
`0
`2 3
`4
`5
`6 7 8
`9 10
`Excitation (watt/cm2)
`
`Fig. 2. Efficiency of Ce: BEL and Ce: YSO as a function of
`excitation po wer density. Ce : BEL does not saturate at high
`excitation power densities.
`
`were excited with an anode potential of 15 kV, and
`the resulting spectrum of cathodoluminescence and
`the cathodoluminescent efficiency were measured.
`Photometry conformed to the C.l.E. photoptic
`curve. Electron beam scanning was with an NTSC
`standard 525 line raster confined to a 3 mm by
`3 mm square in the wafer center. Figure 1 shows
`that the spectrum of Ce: BEL is a blue-shifted ana(cid:173)
`log of the Ce : Y AG spectrum. The efficiency of light
`
`"o
`0 '60
`§=>
`~ 0 0
`~ o o Ce:BEL Fluorescence
`f1
`~
`
`1750
`
`_1500
`~ ·g 1250
`..ci
`~ 1000
`.?;-
`-~ 750
`
`<1> s 500
`
`250
`0~~~~~~~~~~
`0
`25 50 75 1 00 125 150 1 75 200
`Time (nsec)
`
`Fig. 3. Fluorescent decay of Ce : BEL phosphor, as measured
`with a UV excitation pulse derived from a doubled alexandrite
`laser. These data show a decay time of less than 50 ns, similar to
`the decay time of Ce: Y AG.
`
`emission approximately doubled after the hydro(cid:173)
`gen anneal to a value of 0.13 lms/ W. The electron
`beam power was increased in steps to 8.3 W j cm 2
`and no saturation was noted, as seen in Fig. 2. This
`is in contrast to the performance of the Ce: YSO
`blue phosphor, as measured for a wafer from a crys(cid:173)
`tal prepared by the Airtron Division of Litton Sys(cid:173)
`tems, Inc. (200 East Hanover Ave., Morris Plains,
`NJ 07950, telephone (201)-539-5500).
`A rod of Ce : BEL, 5 mm diameter by 48 mm in
`length, was prepared from the crystal and excited
`by a pulse of 375 nm radiation produced by fre(cid:173)
`quency doubling of a 750 nm alexandrite laser. The
`light intensity as a function of time was recorded for
`the excitation pulse and the fluorescence of the
`cerium activated lanthanum beryllate
`rod, as
`shown in Fig. 3. These data demonstrate a fluor(cid:173)
`escence decay time of the order of 50 ns.
`
`Acknowledgments
`
`I am pleased to acknowledge the assistance of
`M. Long in the preparation of the Ce : BEL crystal,
`J. Fleming in the optical fabrication of the crystal
`wafers, and P. Papanestor and J. Krasinski in the
`decay time experiment.
`
`Vizio EX1025 Page 0006
`
`

`

`130
`
`References
`
`D.M. Gualtieri / Journal of Luminescence 60&61 (1994 ) 127- 130
`
`[1] J.M. Robertson and M.W. van Tol, Phys. Stat. Sol. A 63
`(1981) K59.
`[2] J.M. Robertson and M.W. van Tol, Appl. Phys. Lett. 37
`(1980) 471.
`[3] W.F. van der Weg et al., J. Lumin. 24&25 (1981) 633.
`[4] W.F. van der Weg and M.W. van Tol, Appl. Phys. Lett. 38
`(1981) 705.
`
`[5] J.M. Robertson et al., Philips J. Res. 36 (1981) 15.
`[6] J. Shmulovich, G.W. Berkstresser, C.D. Brandle and A.
`Valentino, J. Electrochem. Soc. 135 (1988) 3141.
`[7] G.W. Berkstresser, C.D. Brandle, J. Shmulovich and A.
`Valentino, U.S. Patent No. 4,894,583 (Jan. 16, 1990).
`[8] L.A. Harris and H.L. Yakel, Acta Crystallogr. B24 (1968)
`672.
`[9] C.F. Cline and R.C. Morris, U.S. Patent No. 3,983,051
`(Sept. 28, 1976).
`
`Vizio EX1025 Page 0007
`
`