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0 IEE 2001
6 August 2001
Electronics Letters Online No: 20010892
DOI: 10.1049/el:20010892
N. Ulbrich, G. Scarpa, A. Sigl, J. RoBkopf, G. Bohm, G. Abstreiter
and M.-C. Amann (Walter Schottky Institute, Technical Vniversity of
Munich, Am Coulombwall, 0-85748 Gaiching, Germany)
E-mail: nicolaus.ulbrich@wsi.tu-muenchen.de
References
energy of the quantum well owing to its huge bowing effect. These
two features reveal the possibilities of pushing the wavelength of
lasers on InP substrates to a longer infrared range. We previously
demonstrated InAsNDnGaAsP quantum wells on InP substrates
with a 10K photoluminescence (PL) peak wavelength as long as
2 . 6 [5].
~ In this Letter, we report the first application of this
new alloy in an optoelectronic device. We have succeeded in fabricating I ~ A S ~ , ~ ~ N ~ , ~ ~ / I four-period
~ ~ , ~ ~ GMQW
~ , ~ ~diode
AS/I~P
lasers with a wavelength as long as 2.38 p under 260 K.
KNOLL, B., and KEILMANN, F.: ‘Near-field probing of vibrational
absorption for chemical microscopy’, Nature, 1999, 399, pp. 134137
KNOLL, B., and KEILMANN, F.: ‘Infrared conductivity mapping for
nanoelectronics’, Appl. Phys. Lett., 2000, 77, pp. 3980-3982
SCHIFF, H.I., MACKAY, G.I., and BECHARA, J. in SIGRIST, M.W. (Ed.):
‘Air monitoring by spectroscopic techniques’ (Wiley Interscience,
New York, 1994), Chap. 5, pp. 239-334
BLASER, s., HOFSTETTER, D., BECK, M., and FAIST, J.: ‘Free-space
optical data link using Peltier-cooled quantum cascade laser’,
Electron. Lett., 2001, 37, pp. 778-780
MARTINI, R., GMACHL, C., FALCIGLIA, J., CURTI, F.G., BETHEA, C.G.,
CAPASSO, F.,
WHITTAKER, E.A.,
PAIELLA, R.,
TREDlCUCCI, A.,
HUTCHINSON, A.L.,
SIVCO, D.L.,
and CHO, A.Y.: ‘High-speed
modulation and free-space optical audiohide0 transmission using
quantum cascade lasers’, Electron. Lett., 2001, 37, pp. 191-193
TREDICUCCI, A.,
CAPASSO, F.,
SIRTORI, C.,
BAILLARGEON, J.N., HUTCHINSON, A.L., and CHO, A.Y.:
FAIST, J.,
SIVCO, D.L.,
‘High-power
continuous-wave quantum cascade lasers’, IEEE J. Quantum
Electron.. 1998, 34, pp. 336-343
GMACHL, C.,
TREDICUCCI, A.,
CAPASSO, F.,
HUTCHINSON. A.L.,
SIVCO, D.L., SERGENT, A.M., MENTZEL, T., and CHO, A.Y.: ‘High
temperature ( T 2 425K) pulsed operation of quantum cascade
lasers’, Electron. Lett., 2000, 36, pp. 723-725
HOFSTETTER, D.,
BECK, M.,
AELLEN, T.,
and FAIST, J.: ‘Hightemperature operation of distributed feedback quantum-cascade
lasers at 5.3 pm’, Appl. Phys. Lett., 2001, 78, pp. 396-398
0.54
energy, eV
0.50
0.62
0.58
Fig. 1 Photoluminescence spectrum of laser structure at 10 K
Peak at 0.553eV and full width at half maximum is 42.2meV
lnAs ,9,N,~,,/lnGaAs/lnP multiple quantum
well’lasers with emission wavelength h =
2.38 pm
Ding-Kang Shih, Hao-Hsiung Lin a n d Y.H. Lin
Application of a novel InAsN alloy on a laser device is reported
~
for the first time. The four-period InAso 97No 03-Inos 3 G47A~InP strained multiple quantum well laser, growq by gas source
molecular beam epitaxy with an RF-coupled plasma nitrogen
source, lased under pulsed operation at 2 . 3 8 ~at 260K. A
threshold current density of 3.6Wcm2 at 260K and a
characteristic temperature of 62 K have been achieved.
Introduction: Many spectroscopic and medical applications require
lasers operated within 2 to 3 p n . Traditionally, such lasers have
been developed in InGaAsSb/AlGaAsSb material systems lattice
matched to GaSb substrate [l]. However, the development of Sbbased material systems is handicapped by its very undesirable
properties. GaSb compounds are difficult to etch, they have low
thermal conductivity and dissociate at low temperatures. Owing to
the superior quality of InP substrates over GaSb substrates and
the mature growth and processing technology of the InP alloy system, compressively strained In(Ga)As quantum well structures
have been investigated as an alternative approach [2] in this spectral range. In addition, it is noticeable that the novel III-(N, V)
alloy system has recently been proposed as a possible candidate
for the active region of long-wavelength laser diodes [3]. The
advantage of these materials lies in the huge bowing parameters
induced by the large differences in atomic sizes and electronegativities of N and group V atom. Among these mixed group-V nitride
alloys, the ternary alloy InAsN could be a very promising material
for mid-infrared optoelectronic devices. We have recently demonstrated a 2.2 pn InAs/InGaAs/InP highly strained multiple quantum well (MQW) laser grown by gas source molecular beam
epitaxy (GSMBE) [4]. Using InAsN to replace InAs can alleviate
the critical thickness limitation on the quantum well owing to its
small lattice constant, and can also further reduce the bandgap
1342
200
100
0
400
300
current, mA
500
1027/21
Fig. 2 Output power against injection current of InAsN/InGaA.r ridge
waveguide laser measured under pulsed operation at various temperatures
Threshold current density is 3.6 KA/cm2at 260 K
Layer structure: The laser structure was grown on n+-InPsubstrate
in a VG V-80H GSMBE. Besides the element In and Ga sources
and thermally-cracked ASH, and PH, sources used for producing
group 111 and V molecular beams, an EPI UNI-bulb R F plasma
source was used to generate active N species. Si and Be were used
as the dopant sources. The active layer consists of a four-period
MQW, four 3 nm-thick InAso,97No,03
wells separated by three
40 nm-thick Ino.53Gao,47As
barriers, and the upper and lower
Ino.53Gao,47As
layers which are 122 and 126nm-thick, respectively.
First, for the growth, a 0.5p-thick n+-InP buffer layer was
deposited on the n+-InP substrate, both serving as an n-cladding
layer. The active MQW structure was then grown, followed by the
deposition of the p-cladding layer, a 1 . 7 ~ - t h i c kp-type InP with
ELECTRONICS LETTERS
~~
25th October 2001
-
~
Vol. 37
No. 22
the doping concentration increased from 2 x loL7~ m to- 8~x lo’*
~ m - Finally,
~.
a 0.1 pn-thick p+-InGaAs contact layer was deposited. The growth temperature of the active region was as low as
400”C, and the growth rate of InAsN was 1.5 pih. Additionally,
there were no interruptions in the growth of the MQW. This condition was chosen to inhibit the lattice relaxation of the highlystrained InAsN layer. For InAsN growth, the R F power was kept
at 180W and the nitrogen flow rate was kept at 0.1sccm. A
mechanical shutter was used to control the irradiation of nitrogen
beam during the growth and the R F power was turned off immediately after the MQW growth. The nitrogen incorporation is 3%
in the InAsN well layer. In previous studies [6], we have shown
that after rapid thermal annealing (RTA), both the PL intensity
and linewidth of InAsN quantum well are improved. Therefore,
postgrowth rapid thermal annealing was also processed at 575°C
for 20 min under N ambient.
2.5
1
I
1
2.0
:
:
5
._
1.5
Results: Fig. 1 shows the 10K PL spectrum of the laser structure
after the removal of the upper contact and cladding layer. It can
be seen from the Figure that the PL peak is located at 0.553eV
and the full width at half maximum is about 42.2meV. Fig. 2
shows the optical power against injection curves for ridge
waveguide lasers ( W = 6 pn, L = 942.2 pn) under pulsed operation at a series of temperature from 10 to 260K. The pulse length
and repetition rate are 5 p and 500 Hz. The threshold current, Ifh,
is 203 mA at 260 K, which corresponds to a threshold current density of 3.6KA/cm2.The slope efficiency is degraded rapidly as the
temperature increases. Two possible loss mechanisms are suggested. Firstly, in this beyond 2 p laser, Auger recombination
becomes more significant at lower bandgap energy or higher operating temperature. Secondly, because of the high nitrogen composition (-3%) in the wells, the defects introduced by the small
diameter nitrogen located on arsenic sites and the alloy inhomogeneity are expected to exist in InAsN well even after postgrowth
RTA. Fig. 3 displays the spectrum of the above ridge waveguide
laser at 260 K under pulsed injection at 1.41,,l where the If,, is the
threshold current. It can be seen that lasing occurs in many longitudinal modes. The wavelength of the maximum peak is about
2.38pn, which is much longer than those of laser diodes using
InGaAsiInP or InAsP/InP material systems reported so far. Temperature dependence of threshold current density Jfh for the
InAsN/InGaAs/InP MQW laser is shown in Fig. 4. By fitting our
Jfh data to the equation J f h ( Q= Joexp(T/To),we obtain To = 62K
in the temperature range 5&260 K.
L
.E
cn
._
-
Conclusion: We have grown InAsN-InGaAs-InP four-period
MQW diode lasers with an emission wavelength as long as
2.38 pn using RF-plasma assisted GSMBE. The laser can be operated up to 260 K with a characteristic temperature To of 62 K. To
the best of our knowledge, this is the first report on using InAsN
material as the active medium of a laser structure.
1.o
0.5
0
2340
2350
2360
2370
2380
2390
2400
h, nm
2410
p
J
Fig. 3 Emission spectrum of InA.sN/InCaAs laser device
Acknowledgment: This work was supported by the National Science Council of the Republic of China under Contract No. NSC
89-2215-E-002-034.
0 IEE 2001
31 July 2001
Electronics Letters Online No: 20010894
DOI: IO.1049/e1:20010894
T = 260 K, injection current I = 1.41t,,
Maximum peak is located at 2380nm
Ding-Kang Shih, Hao-Hsiung Lin and Y.H. Lin (Room 419,
Department of Electrical Engineering, National Taiwan University,
Taipei, Taiwan, Republic of China)
E-mail: dkshih@epicenter.ee.ntu.edu.tw
References
CHOI, H.K., and EGLASH, s.J.: ‘High-power multiple-quantum-we11
GaInAsSbiAIGaAsSb diode lasers emitting at 2.1 pm with low
threshold current density’, Appl. Phys. Lett., 1992, 61, (lo), pp.
1154-1 156
FOROUHAR, s.,
KSENDZOV, A.,
LARSSON, A.,
and TEMKIN, H.:
‘InGaAsiInGaAsPiInP strained-layer quantum well lasers at
-2p”, Electron. Lett., 1992, 28, (15), pp. 1431-1432
KONDOW, M.,
NAKAHARA, K.,
50
100
150
200
250
300
temperature, K
Fig. 4 Temperature dependence of threshold current density for ridge
ivaiieguide InAsNLnGaAs laser ( W = 6 p , L = 9 4 2 . 2 ~ )under
pulsed operation
+
experimental data
numerical fit with To = 62K
ELECTRONICS LETTERS
25th October 2001
Vol. 37
KITATANI, T.,
NAKATSUKA, S.,
LARSON, M.C.,
YAZAWA, Y., and UOMI, K.: ‘GaInNAs: a novel
material for long-wavelength semiconductors laser’, ZEEE J. Sel.
Topics Quantum Electron.. 1997, 3, (3), pp. 71.9-730
WANG, J.s., LIN, H.H., and SUNG, L.w.: ‘Room-temperature 2 . 2 ~
InAs-InGaAs-InP highly strained multiquantum-well lasers grown
by gas-source molecular beam epitaxy’, IEEE J. Quantum
Electron., 1998, 34, (lo), pp. 1959-1962
wANG, J.S., LIN, H.H., SUNG, L.w., and CHEN, G.R.: ‘Growth of
InAsN/InGaAs(P) quantum wells on InP by gas source molecular
beam epitaxy’, J. Vac. Sci. Technol. E, 2001, 19, (I), pp. 202-206
WANC, J.s., and LIN, H.H.: ‘Growth and postgrowth rapid thermal
annealing of InAsN/InGaAs single quantum well on InP grown by
gas source molecular beam epitaxy’, J. Vac. Sci. Technol. B, 1999,
17, (5), pp. 1997-2000
No. 22
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