World Journal Of Engineering
APPLICATION OF QUASI-TERNARY InAsSbP COMPOUND
SEMICONDUCTORS FOR THE GROWTH OF QUANTUM SIZE
OBJECTS ON InAs (100) SUBSTRATE
Karen Gambaryan 1, *, Vladimir Aroutiounian 1, Vardan Harutyunyan 1,
Torsten Boeck 2, Jan Schmidtbauer 2 and Roman Bansen 2
1
Department of Physics of Semiconductors and Microelectronics, Yerevan State University,
1 A. Manoogian, Yerevan, 0025 Armenia. ( * E-mail: kgambaryan@ysu.am )
2
Leibnitz Institute for Crystal Growth (IKZ), 2 Max-Born-str., Berlin, 12489 Germany.
Introduction
A large research effort has been devoted to quantum
dots (QDs), the quantum wires, QD chains, quantum
rings, nanoholes and pits [1-8] due to their modified
density of states, fascinating optoelectronic properties
and device applications for lasers, photodetectors and
other electronic devices. Among quantum size objects
fabrication techniques, the self-organized StranskiKrastanow method is an important one by which
dislocation-free nanostructures can be produced.
Extensive experimental results suggest that surface
morphologies are relying on growth conditions and
matrix materials. On the basis of an atomistic model, it
is shown that the energy change due to the step
formation is negative or positive depending upon the
sign of the misfit. The step formation energy can even
be negative for compressive misfit stress in the
heterolayer, while it is definitely positive for tensile
misfit stress. Narrow band-gap III–V semiconductor
materials as InAs, GaSb, InSb and their alloys are
particularly interesting and useful since they are
potentially promising to access mid– and far infrared
wavelength regions and should provide the next
generation of semiconductor devices for applications
such as infrared gas sensors, molecular spectroscopy
and thermal imaging, as well as thermophotovoltaic
cells. In this paper we present an example of InAsSbP
quaternary lens-shape and ellipsoidal QDs growth on
InAs (100) substrates by liquid phase epitaxy (LPE).
Experimental procedures
The InAsSbP quantum-size objects are grown from the
thin liquid phase using a LPE slide-boat crucible. The
technological know-how to obtain a very thin (~100200 μm in height) working liquid phase was developed
and applied. To ensure a high purity of the structures,
the entire growth process is performed under the pure
hydrogen atmosphere. The InAs (100) substrates have
an 11 mm diameter, are undoped, with a background
electron concentration of n=2×1016 cm-3. The initial
growth temperature were chosen within T=540-560oC. To
expect the strain-induced QDs formation, the undoped and
supersaturated by antimony and phosphorus liquid phase
was used to provide a different sign of lattice mismatch up
to 2% between the InAs substrate and InAsSbP wetting
layer. To initiate the growth of QDs, a supersaturation of
the liquid phase is developed by decreasing the initial
growth temperature up to 2oC at the slower ramp rate. To
study the QDs morphology, size, shape and distribution
density the high resolution Scanning Electron Microscope
(SEM-EDXA–FEI Nova 600–Dual Beam) and atomic
force microscope (AFM–Asylum Research MFP-3D) are
used.
Results and discussion
A series of QDs structures were grown at the different
initial growth temperatures and the liquid phase
compositions, as well as at the different in height liquid
phases. The optimal technological conditions were chosen
for the growth of lens-shape and the ellipsoidal QDs,
quantum rings, QDs/nanopits cooperative structures in
InAsSbP quasi-ternary material system. In Fig. 1 the AFM
– (A, B) and HR-SEM – (C, D) images of the InAsSbP
lens-shape and ellipsoidal QDs grown by LPE on InAs
(100) substrate are presented. From these figures the
bimodal growth mode is quite visible, i.e. QDs massive
consists of relatively uniform distributed small QDs in
sufficiently large (~300 μm2) area with the more low
density and relatively big QDs. Statistical explorations
shown that the small QDs average density ranges from 3
to 9×109 cm-2, with heights and widths dimensions from
0.8 nm to 15 nm and 10 nm to 40 nm, respectively.
Otherwise, the less density and big QDs average diameter
ranges from 40 to 80 nm. In Fig 2 is also presented an
example of InAsSbP quantum dot molecule in the form of
QD/nanopits cooperative structure taken from our
previous work [3]. Our detailed analysis shown that small
QDs are mainly lens-shape, but the bigger ones –
ellipsoidal, and that the elongation occurs mainly in [010]
direction. Note, that the interesting transformation of the
QDs histograms and the distribution function’s shape, i.e.
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World Journal Of Engineering
dependence of the QDs number versus their average
diameter, was detected (Fig. 3). In particularly, the
small QDs distribution is well fitted by the GramCharlier function (Lifshitz-Slezov-like distribution
with the “left” asymmetry), but ellipsoidal QDs – by
the Gaussian.
(A)
(B)
active surface, and (ii) p-InAsSbP/n-InAs diode
heterostructures with QDs inside p-n junction spatial
charge region.
Conclusion
Thus, we have presented an example of the InAsSbP
quaternary lens-shape and ellipsoidal QDs grown by LPE
on InAs (100) substrate. Bimodal growth mechanism for
the QDs was observed. It was shown that during the
growth an elongation of QDs and their shape
transformation from lens-shape to ellipsoidal are occurred.
The small QDs distribution is well fitted by the GramCharlier function, but ellipsoidal QDs – by the Gaussian.
The results of our study can be used for the fabrication of
novel QDs-based semiconductor devices for several midinfrared applications.
Acknowledgments
(C)
(D)
Fig. 1. AFM – A, B and HR-SEM – C, D images of the
InAsSbP lens-shape and ellipsoidal QDs grown
by LPE on InAs (100) substrate.
Fig. 2. HR-SEM image of the InAsSbP QD molecule in
the form of QD/nanopits cooperative structure.
Fig. 3. Number of QDs versus their average diameter.
On the base of researches presented in this paper a two
type of quantum dot mid-infrared photodetectors are
fabricated: (i) photoconductive cells with QDs on the
This work was performed in the frame of German
Academic Exchange Service Award (2010) and in part by
a Research Grant from the Armenian National Science and
Education Fund (ANSEF, 2011) based in New York,
USA.
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