International audienceIn this paper, we report on a detailed investigation of the effect of misorientated InP(OOl) substrates on the optical properties of InAs quantum islands grown by molecular beam epitaxy in the Stranski-Krastanow regime. Temperature-dependent photoluminescence and polarization of photoluminescence (PPL) are studied. PPL shows a high degree of linear polarization, near 40%, for the sample grown on the substrate with 2°off miscut angle towards [110] direction (2°F) and only 16% for the sample grown on the substrate with 2°off miscut angle towards [010] direction (2°B). This result pointing out the growth ofInAs quantum wires (QWr) on 2°F substrate and of quasi-isotropic InAs quantum dots (QD) on 2°B substrate. The luminescence remains strong at 300 K as much as 36% of that at 8 K, indicating a strong spatial localization of the carriers in the InAs QIs grown on InP(OOl)

Brault, J.

Bremond, G.

Gendry, M.

Guillot, G.

Hollinger, G.

Maaref, H.

Monat, C.

Olivares, J.

Salem, B.

English

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HAL Id: hal-02165357
https://hal.archives-ouvertes.fr/hal-02165357
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Optical anisotropy and photoluminescence temperature
dependence for self-assembled InAs quantum islands
grown on vicinal (001) InP substrates
B. Salem, J. Olivares, J. Brault, C. Monat, M. Gendry, G. Hollinger, H.
Maaref, G. Guillot, G. Bremond
To cite this version:
B. Salem, J. Olivares, J. Brault, C. Monat, M. Gendry, et al.. Optical anisotropy and photolumines-
cence temperature dependence for self-assembled InAs quantum islands grown on vicinal (001) InP
substrates. Microelectronics Journal, Elsevier, 2002, 33, pp.579 - 582. ￿hal-02165357￿
ELSEVIER Microelectronics Journal 33 (2002) 579-582
Microelectronics
Journal
www.elsevier.comJlocate/mejo
Optical anisotropy and photoluminescence temperature dependence for
self-assembled InAs quantum islands grown on
vicinal (001) InP substrates
B. Salema,*, J. Olivaresa, J. Braultb, C. Monatb, M. Gendryb, G. Hollingerb, H. Maarerc,
G. Guilloe, G. Bremonda
"INSA de Lyon. LPM (UMR 55II CNRS). 69621 Villeurbanne. France
bEcoie Centrale de Lyon. LEOM (UMR 5512 CNRS). Ecully. France
CFaculte des Sciences de Monastir. Monastir. Tunisie
Abstract
In this paper, we report on a detailed investigation of the effect of misorientated InP(OOl) substrates on the optical properties of InAs
quantum islands grown by molecular beam epitaxy in the Stranski-Krastanow regime. Temperature-dependent photoluminescence and
polarization of photoluminescence (PPL) are studied. PPL shows a high degree of linear polarization, near 40%, for the sample grown on the
substrate with 2° off miscut angle towards [110] direction (2°F) and only 16% for the sample grown on the substrate with 2° off miscut angle
towards [010] direction (2°B). This result pointing out the growth ofInAs quantum wires (QWr) on 2°F substrate and of quasi-isotropic InAs
quantum dots (QD) on 2°B substrate. The luminescence remains strong at 300 K as much as 36% of that at 8 K, indicating a strong spatial
localization of the carriers in the InAs QIs grown on InP(OOl). © 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Optical anisotropy; Photoluminescence; InP substrates; Quantum islands
1. Introduction
In recent years, much attention has been devoted to the
fabrication and the characterization of self-assembled
quantum dots (QDs) [1,2], which are important for both
fundamental studies and optical applications such as ultra-
low-threshold current lasers [3]. However, the emission
wavelength ofthe (In, Ga)As QDs grown on GaAs is limited
to the 0.9-1.3 f.Lm range which does not match the usual
wavelength for optical communications. In order to reach
1.55 f.Lm, InAs QDs on InP are promising candidates [4].
Due to a 3.2% lattice mismatch ofInAs on InP(OOl), elastic
strain relaxation takes place above a certain critical thick-
ness via a change of morphology from two-dimensional
(2D) to three-dimensional (3D). Much of the research devel-
oped on self-organized growth of InAs on InP substrates is
devoted to quantum island (QI) formation [4-7]. Among
them, the growth on vicinal surfaces allows a lateral prefer-
ential growth at the surface step edges. Few studies of InAs
QDs formation on misoriented (001) InP substrates have
been reported [8-10]. In this work we report on the optical
* Corresponding author.
E-mail address:salem@insa-lyon.fr (B. Salem).
anisotropy and the temperature-dependent photolumin-
escence (PL) measurements of InAs Qls grown on vicinal
2°F and 2°B (001) InP substrates via solid-source molecular
beam epitaxy (MBE).
2. Experimental details
The samples investigated in this study were grown by
solid-source MBE in a Riber 2300 reactor. InAs self-
assembled Qls were grown on semi-insulating InP(OOl),
simultaneously on 2° off miscut angle towards [110] direc-
tion and 2° off miscut angle towards [010] direction
substrates. Before the growth, the substrates were heated
up to 535°C for a few minutes in order to remove the native
oxide. Then a 300-nm-thick InP buffer was grown at 480°C
at 1 f.LmIh growth rate using a phosphorus pressure equal to
1 X 10-5 Torr. Three monolayers (ML) ofInAs were grown
at 520°C with a reduced growth rate of 0.25 f.LmIh (0.22MLI
s) and an arsenic pressure fixed at 4 X 10-6 Torr. The 3D
growth onset is observed by reflection high electron energy
diffraction (RHEED) at 1.8ML. Uncapped islands were
imaged using ex situ atomic force microscopy (AFM),
using a Park Scientific Instruments microscope, model CP,
operating in the contact mode [13]. In order to characterize
0026-2692/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PH: S0026-2692(02)00022-8
580 B. Salem et at. I Microelectronics Journal 33 (2002) 579-582
3. Results and discussion
3.1. Temperature-dependent PL measurement
Fig. lea) shows the PL spectra measured at several
temperatures for the 2°B sample excited with an Ar +-ion
laser. The excitation power is 200 mW. The PL spectrum at
8 K shows a broad luminescence peak at 0.834 eV; the peak
has an asymmetric shape with a tail at the high-energy side.
The full width at half maximum (FWHM) of the PL peak is
approximately 115 meV. In order to study band filling
phenomena, which may affect PL spectra shape due to the
presence of excited states in the QIs, the linearity of the PL
intensity with excitation power density has been measured,
at 8 K, from 0.6 to 3100 W/cm2. The broad PL peak could
rather originate from the size inhomogeneity of the InAs
QIs. Indeed the smaller InAs QIs would emit at the higher
energy side of the broad and the larger InAs QIs at the lower
energy side. Therefore, the asymmetric shape of the PL peak
with a high-energy tail would indicate that the larger InAs
QIs are more numerous than the smaller InAs QIs. The PL
spectrum at 8 K from the 2°F sample consists of several
sharper bands (Fig. l(b». The measured line-widths of
such individual lines are about only 45 meV, to be
compared with the 115 meV on the previous sample. No
PL intensity transfer from low to high-energy peaks has
been observed versus the excitation power density. This
evidences that these individual lines can be attributed to
the size fluctuation of the InAs QIs. No emission from the
wetting layer is observed, indicating that carriers photo-
generated diffuse quickly from the wetting layer to the
adjacent InAs QIs.
The PL integrated intensity for the two QIs structures as a
function of temperature is shown in Fig. 2. We clearly
observe two different regimes in temperature dependence.
The integrated intensity is quite stable in the 8-100 K range
and decreases for temperatures higher than 100 K. The
decrease of the integrated PL emission at higher tempera-
ture is related to exciton dissociation, and consequent
electron-hole pairs escape from the QIs. The temperature
at which the exciton dissociation is observed is quite higher
than that of quantum wells (QWs) and even other QDs
reported elsewhere. The thermal activation energy of
electron-hole emission from an InP barrier to the quantum
dots was measured to be 79 meV for both samples.
Finally, we show that the PL intensity remains very
strong at room temperature, as much as 36% of its value
at 8 K for the 2°B sample and 30% for the 2°F sample. This
behavior suggests that the photo-generated carriers
--8K
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190K
_._- 240K
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the carrier confinement in these QIs with PL measurements,
the samples were held 10 s under arsenic pressure at growth
temperature and then were covered with a 40-nm-thick InP
layer grown at 0.25 f.unlh using a phosphorus pressure of
4 X 10-6 Torr and finally with a 260-nm-thick InP cap layer
grown at I fLmIh. The PL spectra were obtained in the
8-300 K temperature range. The PL was excited using
either the 514.5 nm line of an Ar +-ion laser or a 1064 nm
line of a YAG laser. The PL emission was dispersed by a
high resolution grating spectrometer and detected by a 77 K
cooled Ge photodetector using a conventional lock-in
technique. The polarization measurements were performed
on the PL emission normal to the surface via a Glan-
Thompson near infrared polarizer at the entrance slit of
the monochromator followed by a quarter wave plate in
order to get the PL signal independent of any light polariza-
tion effect of the optical system response.
Fig. 1. PL spectra at several temperatures of the 2°F sample (a) and 2°B
sample (b).
--8K
- - - 100K
····200K
_._.- 300K
Fig. 2. Temperature dependence of the integrated PL intensity. The ther-
mal-activation energy of electron-hole emission through an InP barrier
calculated from the figure is measured at 79 meV.
1-_- 2"8 I
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B. Salem et at. / Microelectronics Journal 33 (2002) 579-582 581
(1)
recombine mostly in the QIs without escaping to the barrier
layer even at room temperature.
3.2. Polarization photoluminescence studies
PL polarization measurements were performed in the
linear response regime with an excitation spot diameter of
300 !-Lm. The degree of linear polarization P of the emitted
light is classically defined by the following equation:
P = 1[110] - 1[110]
1[110] + 1[110]
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Fig. 4. Polarization PL spectra at 8 K and degree of linear polarization for
the 2°F sample (a) and for the 2°B sample (b).
while a strong PPL signal corresponding to InAs quantum
wires is observed on the substrate tilted 2° off towards [110].
We have also shown a great stability of the integrated PL
intensity in the 8-300 K temperature range according to a
strong localization of photo-carriers in the InAs QIs grown
on InP(OOI). Finally, the PL intensity remains very strong at
room temperature, as much as 36% of its value at 8 K for the
2°B sample which corresponds to the best results obtained
up to now on 111-V quantum dots. Finally, this work points
out that the optical properties of these InAs/lnP QDs are
very close to those needed for laser device applications
and that PPL spectroscopy can efficiently be used as a
way to check and estimate, just after growth, the wire
shape or the isotropic shape of QIs.
4. Conclusion
where 1[110] and 1[110] are the PL intensities along the two
orthogonal directions [1 fO] and [110]. No PL polarization
anisotropy is observed for a InAs/InP quantum well (Fig. 3).
On the 2°F sample, a strong anisotropy is observed; the two
peaks observed at 0.964 and 1.038 eV are related to the
YAG laser. In fact, the PL peak intensities observed in the
[110] direction of the polarizer are twice smaller than that
observed in the [1 fO] direction.
The degree of linear polarization of the 2°F sample is
found to be around 40% (Fig. 4(a». This result is the clear
signature of quantum wires (QWr). We also observed that
the degree of linear polarization gradually decreases with
the increase of the photon energy. This suggests that large
size QWr have stronger optical anisotropy than small ones
as was also evoked for InP/lnGaP and InAs/GaAs(311) QDs
[11,12]. In contrast, the degree of linear polarization of the
2°B misoriented sample is only 16% (Fig. 4(b». These
results reveal that the 2° growth on miscut angle towards
[010] substrate leads to grow more isotropic self-assembled
InAs/lnP QDs.
In conclusion, PL and polarization photoluminescence
(PPL) spectroscopies have allowed to study the optical
properties of InAs QIs grown on InP(OOI) and their depen-
dence on substrate misorientation. We have shown that on
the 2° off miscut angle towards [010] substrate, we obtain a
PPL signature related to quasi-isotropic InAs quantum dots
Fig. 3. Polarization PL spectra at 8 K and degree of linear polarization for
the InAs/lnP quantum welL
[1] P.M. Petroff, S.P. DenBaars, Superiattices Microstruct. 15 (1994) 15.
[2] Y. Nabetani, T. Ishikawa, S. Noda, A. Sasaki, J. AppL Phys. 76 (1994)
347.
[3] C. Weisbuch, B. Vinter, Quantum Semiconductor Structures, Funda-
mentals and Applications, Academic press, San Diego, 1991.
[4] S. Fafard, Z. Wasilewski, J. McCaffery, S. Raymond, S. Charbon-
neau, AppL Phys. Lett. 68 (1996) 991.
[5] A. Rudra, R Houdre, J.F. Carlin, M. llegems, J. Cryst. Growth 136
(1994) 278.
[6] H. Marchand, P. Desjardins, S. Guillon, J.-E. Paultre, Z. Bougrioua,
RY.-F. Yip, RA. Masut, AppL Phys. Lett. 71 (1997) 527.
[7] A. Ponchet, A. Le Corre, H. L'Haridon, B. Lambert, S. Salatin, AppL
Phys. Lett. 67 (1995) 1850.
References
i-----------;::=======::;l1.0
08 §
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- - - (:5), ~ - 0.0 ro
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-0.6 Q)
Q)
M ~8~
L-'-----~'------''____c"''_::__"'----c"'~---'~------'~---'-~----.J -1.0 ~
0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30
Energy (eV)
8.0x1012
::J
~
~
'in 4.0x1012
c:
$
c:
...J
ll.
582 B. Salem et al. / Microelectronics Journal 33 (2002) 579-582
[8] R. Leonelli, C.A. Tran, J.L. Brebner, J.T. Graham, R. Tabti, R.A.
Masut, S. Charbonneau, Phys. Rev. B 48 (1993) 11135.
[9] N. Lebouche-Girard, A. Rudra, E. Kapon, J. Cryst. Growth 175
(1997) 1210.
[10] P. Paki, R. Leonelli, L. Isnard, R.A. Masut, J. Appl. Phys. 86 (1999)
6789.
[11] M. Sugisaki, HW. Ren, S. Nair, Phys. Rev. B 59 (1999) R5300.
[12] M. Henini, S. Sanguinetti, S.C. Fortina, E. Grilli, M. Guzzi,
G. Panzarrini, L.c. Andreani, M.D. Upward, P. Moriarty, P.H.
Beton, L. Eaves, Phys. Rev. B 57 (1998) R6815.
[13] B. Salem, J. Olivares, G. Guillot, G. Bremond, J. Brault, C. Monat,
M. Gendry, G. Hollinger, F. Hassen, H. Maaref, Appl. Phys. Lett. 79
(2001) 4435.


Optical anisotropy and photoluminescence temperature dependence for self-assembled InAs quantum islands grown on vicinal (001) InP substrates

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Optical anisotropy and photoluminescence temperature dependence for self-assembled InAs quantum islands grown on vicinal (001) InP substrates

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