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Note that, for m + 00 (steady-signal case), accounting for
the well-known relation
HIGH QUALITY 0.98pm GalnAs/GaAs/GalnP
LASERS GROWN BY CBE USING
TERTIARYBUTYLARSINE A N D
TERTIARY BUTYLPHOSPHINE
J. C. G a r c i a , P h . M a u r e l and J. P. Hirtz
and the integral representation of the modified Bessel functions, the BER expression given by eqn. 11 reduces to that of
eqn. 3 with yo replaced by y.
Indexing terms: Epitaxy and epitaxial growth, Semiconductor
lasers
Hlgh quality GalnAs/GaAs/GaInP laser structures were
grown by chemical beam epitaxy using tertiarybutylarsine
(TBAs) and tertiarybutylphosphine (TBP) under pulsed conditions. For a 300gm long cavity, a threshold current density
of 390A/cm2 and external quantum efficiency of 0.6W/A
(two facets) were obtained, which are typical for this kind of
structure. This demonstrates the suitability of TBP and
TBAs as substitutes of arsine and phosphine in chemical
beam epitaxy for laser fabrication.
a
a
5
0
10
15
20
Yo.dB
Fig. 1 BER of DQPSK signals in Nakagamr fading for several ualues of
m
As regards the particular case of Rayleigh fading (m = l),
accounting for eqn. 3.613/1 of Reference 7, it can be rcognised
that the series in eqn. 11 is a geometric series. Therefore, we
obtain the BER expression of DQPSK signals in Rayleigh
fading and AWGN:
P,
1
=
241
+ 4y0 + 2
~ 3
This particular result was first derived in Reference 8.
In conclusion, a new BER expression has been presented,
which can be used for mobile radio systems with DQPSK
modulation format, operating in AWGN environments and
slow fading conditions.
6th January 1993
M. Tanda (Universita di Napoli, Dipartirnento di Ingegneria Elettronica, Via Claudio 2 1 , 1 4 0 1 2 5 Napoli, Italy)
References
1
SUZUKI, H.:‘A
2
‘Characteristicsof a digital mobile radio channel’,IEEE
Trans., 1981, VT-30, pp. 45-53
M.:‘The m-distribution-A general formula of intensity
NAKAGAMI,
distribution of rapid fading’, in: ‘Statistical methods of radio wave
propagation’ (Pergamon Press, Oxford, 1960)
HOOVER, U. M.:‘An instrument for testing North Amencan digital
cellular radio’, Hewlett Packard J., 1991,42, pp. 65-72
PROAKIS, I.: ‘Digital communications’ (McGraw-Hill, New York,
1989),2nd edn.
ABRAMOWiTZ, M., and STEGUN, I. (Eds.):‘Handbook of mathematical functions’(Dover Publications, Inc., New York, 1972)
GRAUSHTEVN, I. s., and RYZHIK, I. M.:‘Tables of integrals, series, and
products’ (Academic Press, Inc., New York, 1980), Revised edn.
TJHUNG, T. T., CHUN LOO, and SECORU. N. P.: ‘BER performance of
DQPSK in slow Rician fading’, Electron. Lett., 1992, 28, (18), pp.
1763-1765
statistical model for urban multipath propagation’,
IEEE Trans., 1977, COM-25, pp, 673-680
3
4
5
6
7
8
AULIN, T.:
432
More and more attention is currently being paid to reduce the
hazards in 111-V growth technologies such as metal organic
chemical vapour deposition (MOCVD), chemical beam
epitaxy (CBE) of gas source molecular beam epitaxy
(GSMBE) which use highly toxic gases such as arsine (ASH,)
or phosphine (PH,). The most common organometallic
sources sources proposed as substitutes for arsine and phosphine are tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP). These two products have now been widely used
for the MOCVD epitaxial growth of GaAs and I n P based
microwave and optoelectronic devices [l-31, leading to comparable performances with those obtained with P H , and
ASH,. In contrast, only a few reports have been presented o n
CBE grown material [4-61 and, to our knowledge, no report
has been presented on the device performances of CBE grown
structures without the use of hydride gaseous sources.
We report for the first time the fabrication of high quality
GaAs/GaInAs/GalnP 0.98 pm laser diodes grown with TBP
and TBAs. 0.98 pm pump laser diodes have now been extensively developed for use in optical systems involving Er doped
silicon fibres [7] or Er doped glasses [8]. The structure of the
diodes is generally a GaInAs/GaAs/GaAlAs graded index
separate confinement heterostructure single quantum well
(GRINSCH-SQW). However, the A1 containing structures
generally suffer from reliability problems due to defect propagation originating from the GaAlAs layers [SI. Therefore,
replacement of GaAlAs by G a l n P has been proposed and
GaInAs/GaAs/GaInP laser structures emitting at 0.98 pm
have been developed [lo, 111.
The GaInAs/GaAs/GaInP laser structures were grown on
(100) oriented n-GaAs substrates in a CBE 32 Riber machine.
Trimethylindium (TMIn) and triethylgallium (TEGa)
organometallic sources are used as the starting materials for
group 111 elements. The TBP and TBA bubbler temperatures
were kept at room temperature. No carrier gas is used due to
the high vapour pressure of these precursors, which permits
direct control of the flow rate by usual mass flow controllers.
The cracking temperatures of T B P and TBAs were fixed to
900 and 700”C, respectively. More details on the growth
experiments will be reported elsewhere. Previous experiments
[121 revealed a significant reduction in carbon incorporation
of at least one order of magnitude in G a I n P when TBP is
used instead of phosphine. Solid beryllium (Be) and gaseous
hydrogen sulphide (H,S) are used as p and n type dopant
sources, respectively. The active region of the device is made
of three 70A thick GaInAs uantum wells, with 200A thick
GaAs barriers, with a l o 0 0 ~thick GaAs optical cavity on
each side and 1.2pm thick n (N, = 2 x l O ’ * ~ m - ~and
)
p
( N o = 2 x 1 0 ’ * ~ m - ~type
)
G a I n P cladding layers. A p+
(N, = 5 x 10’9cm-3) GaAs cap layer is grown on top of the
structure for ohmic contact formation.
After growth, a standard photolithographic technique was
used to define large area lasers with widths varying between
40 and 100pm. Fabry-Perot cavities with lengths varying
between 190 and 860pm were then cleaved and the individual
diodes were then characterised under pulsed conditions. Selected diodes are presently being mounted on copper heatsinks
ELECTRONICS LETTERS 4th March 1993 Vol. 29 No. 5
for power measurements and results will be published elsewhere
Acknowledgments: We thank D. Leguen for material growth,
C. Grattepain for SIMS experiments, A. Friederich and J.
Nagle for constant interest and encouragement. This work has
been partially supported by the Commission of the European
Community through the 5031 ‘MORSE‘ ESPRIT project.
7th January 1993
J. C. Garcia, Ph. Maurel and J. P. Hirtz (Laboratoire Central de
Recherckes, Thomson CSF, Domaine de Corbeville F-91404 Orsay
Cedex, France)
It
References
M., SATO, K., and KoNDO, Y . : ‘Metalorganic vapor
phase epitaxial growth and 1.5pm laser fabrication using ethyldimethylindium, tertiarybutylphosphine and tertiarybutylarsine’,
Appl. Phys. Lett., 1992,60, pp. 1217-1219
2 KIM, T. s., BAYRAKTAROGLU, B., HENDERSON, T. s., and PLUMTON, U.
L.: ‘Organometallic vapor phase epitaxy of AIGaAslGaAs heterojunction bipolar transistors using tertiarybutylarsine’. Appl. Phys.
Lett., 1991,543, pp. 1997-1999
3 OUGAZZADEN, A., MELLET, R., GAO, Y., KAZMIERSKI,K., RHEIN, c., and
MIRCEA, A.: ‘State of the art 1.3pm lasers by atmospheric pressure
MOVPE using tertiarybutylphosphine’, Electron. Lett., 1991, 27,
pp. 1005-1006
4 RITTEK D., PANISH, M. B., HAMM, R. A., GERSHONI, G., and BRENER, I.:
‘Metalorganic molecular beam epitaxy of InP, GaInAs and GaAs
with tertiarybutylarsine and tertiarybutylphosphine’, Appl. Phys.
Lett., 1990,56, pp. 1448-1450
5 HINCELIN, G. ZAHOUH, M., MELLET, R., and H)UGNET, A. M.: ‘Growth
of InP in CBE with high purity tertiarybutylphosphine’, J. Cryst.
Growth, 1992,120, pp. 119-123
6 BEAM 111, E. A., HENDERSON, T. s., SEABAUGH, A. c., and YANG, J. Y . :
‘The use of tertiarybutylphosphine and tertiarybutylarsine for the
metalorganic molecular beam epitaxy of GalnAs/InP and GaInP/
GaAs materials systems’, J. Cryst. Growth, 1991, 116, pp. 436-446
7 SCHMUCK, H., PFEIWER, TH., and VEITH, G.: ‘Widely tunable narrow
linewidth erbium doped fibre ring laser’, Electron. Lett., 1991, 27,
pp. 21 17-2119
8 LAFQRTA, P., LONFHI, S., TACCHEO, S., SVELTO, O., and SACTHI, G.:
‘10 kHz linewidth diode-pumped Er : Yb glass laser’, Electron.
Lett., 1992, 28, pp. 2067-2069
9 WANG, c. A., and GROVES, s. H . : ‘New materials for diode laser
pumping of solid state lasers’, IEEE J. Quantum Electron., 1992,
QE-28, pp. 942-951
10 ZHANG, G., NAPPI, I., VANTINNEN, K., ASONEN, H., and PESSA, M . : ‘LOW
threshold current InGaAs/GaAs/GaInP lasers grown by gassource MBE, Appl. Phys. Lett., 1992,61, pp. 96-98
1
3
E
a
>
>
I ,mA
Fig. 1 Pulsed light output power per facet as Junction of injection
current, and current-voltage characteristic for GalnAs/GaAs/GaInP
SCH-MQW laser IWpm wide and 320pm long at 20°C
Fig. 1 shows pulsed light output power per facet as a function of injection current, together with the current-voltage
characteristic, for a 100pm wide, 320pm long device at room
temperature. The threshold current density and the external
quantum efficiency of this diode are, respectively, 390A/cm2
and 0.6W/A (two facets). The threshold current density
decreases down to 300A/cmZ for a n 860pm long cavity and
the external quantum eficiency increases up to 0.66 W/A for a
190pm long cavity. Fig. 2 shows the dependence of the inverse
of external quantum efficiency with cavity length. The straight
line through the points yields an internal quantum etliciency
of 60% and the internal waveguide losses calculated from the
slope of the line are 1Ocm-I, values which are typical for this
kind of device.
11
OGASAWARA,
MAUREL, PH., GARCIA, I. C., REGREW, PH., HIRTZ, I. P . , VASSILAKIS, E.,
BALDY, M., PARENT, A., and C A R R I ~ R E ,c.: ‘Room temperature
MX)mW CW output power per facet from a single GaInAs/GaAs/
GaInP large area laser diode grown by CBE, Efectron. Lett., 1993,
29, (I), pp. 91-93
12 GARCIA, J. c., REGREW, PH., DELAGE, s., BLANCK, H., and HIRTZ, 1. P.:
‘Chemical beam epitaxy of GaInP using tertiarybutylphosphine’.
Proc. 7th Int. MBE Conf., Stuttgart, 1992 (to be published in J .
Cryst. Growth)
PREDICTION SIGNAL CONTROLLED SCANS
FOR IMPROVED MOTION COMPENSATED
VIDEO CODING
H. Schiller
0
200
400
600
cavity lenglh,pm
800
1000
Indexing terms’ Video, Image coding
Fig. 2 Reciprocal differential quantum efficiency of GalnAslGaAsl
GaInP lasers against cavity length
In summary, tertiarybutylphosphine and tertiarybutylarsine
have been successfully used as the replacements for phosphine
and arsine in the realisation of GaInAs/GaAs/GaInP 0.98
lasers by CBE. Hydride-free lasers exhibit low threshold
current density and internal losses and high external quantum
efficiency. This confirms the suitability of these phosphorus
and arsenic sources for high performance laser structures
growth with CBE.
ELECTRONICS LETTERS 4th March 1993 Vo/. 29
No. 5
Interdependencies between prediction signal and prediction
error in predictive coding schemes are investigated. Without
additional side information, adaptive scan paths for DCT
and nontransform coding of prediction error blocks can be
derived from the prediction signal gradient. Simulations indicate that these paths efficientlyscan some blocks when used
alternatively to zigzag scan.
Introduction: For digital coding of image sequences with a
moderate degree of motion, hybrid coding schemes have
gained increasing popularity. In state-of-the-art hybrid
433
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