The formation of nanodimensional InAs crystallites on Si wafers was studied by the method of high fluence implantation of As and In ions with subsequent high temperature treatment. It was found that the size and depth distributions of the crystallites depend on both the implantation temperature and the annealing conditions. A broad band in an energy range of 0.75–1.1 eV was recorded in the photolumines  cence spectra of the samples

Komarov, A. F.

Komarov, F. F.

Mil’chanin, O. V.

Mudryi, A. V.

Vlasukova, L. A.

Wesch, V.

English

Электронная библиотека БГУ

ISSN 10628738, Bulletin of the Russian Academy of Sciences: Physics, 2010, Vol. 74, No. 2, pp. 252–255. © Allerton Press, Inc., 2010.
Original Russian Text © F.F. Komarov, O.V. Mil’chanin, L.A. Vlasukova, W. Wesch, A.F. Komarov, A.V. Mudryi, 2010, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya
Fizicheskaya, 2010, Vol. 74, No. 2, pp. 273–276.
252
INTRODUCTION
The synthesis of directgap semiconductors A3B5
in a Si matrix is of interest in designing the next gener
ation of photodetectors and lightemitting diodes
based in silicon technology. We earlier reported we had
obtained coherent InAs nanocrystals in Si (001) by the
hot highfluence implantation of As and In ions with
subsequent annealing [1]. In this work, we present the
results from studying the effect of the implantation
and annealing regimes on the processes of the ion
beam synthesis of InAs nanocrystals in silicon.
EXPERIMENTAL
Silicon wafers were first implanted with As ions
(245 keV, 4.1 × 1016 cm–2) and then with In ions
(350 keV, 3.7 × 1016 cm–2) at 25 and 500°С. Part of the
samples implanted with heavy ions at room tempera
ture were additionally exposed to  ions with an
energy of 100 keV and a fluence of 1.2 × 1016 cm–2 in
terms of atomic hydrogen. This procedure was per
formed to obtain an internal getter at a depth about of
500 nm during postimplantation annealing. The
samples were subsequently annealed in an inert ambi
ent (900°C, 60 min). The fluences of hot ion implan
tation were reduced by a factor of 1.5 and the anneal
ing duration was increased (from 30–45 to 60 min) as
compared to the experiment described in [1]. To ana
lyze the depth distributions of the implanted impuri
ties and to study the structural and optical properties
of the samples, we applied the methods of Rutherford
backscattering (RBS), transmission electronic
microscopy (TEM), and photoluminescence (PL).
H2
+
RESULTS AND DISCUSSION
Figure 1 presents the RBS spectra of the samples
under study. Analysis of the spectra shows that implan
tation at room temperature results in the formation of
an amorphous layer with a thickness of 330–350 nm.
Subsequent annealing leads to a restoration of the
crystal structure and to a significant redistribution of
impurities. An significant decrease in the amount of
implanted impurity is observed; in addition, about half
the arsenic atoms are in lattice sites. After heat treat
ment, the random spectra of samples with and without
a getter coincide. In the aligned spectrum of a sample
with a getter, however, in the channel range from 150
to 220, the yield of backscattered He+ ions is less (by
10%) than in a sample without a getter. In the case of
hot implantation, no amorphization of the nearsur
face region is observed. In our opinion, the increase in
the yield of backscattered He+ ions in the aligned
spectrum (spectra from 170 to 190) corresponds to a
region of imperfections located deeper in the sample
(as compared to the impurity maximum). The incor
poration of part of the impurities into the silicon lat
tice sites is observed immediately after hot implanta
tion. Hightemperature annealing of the given sam
ples leads to further significant restoration of the
silicon matrix’s crystal structure, and to the incorpo
ration of approximately half of the implanted impuri
ties into the silicon matrix sites.
Figure 2 shows the depth profiles of In and As in
silicon samples simulated (SRIM’2003) and calcu
lated from the experimental RBS spectra. The calcu
lation of As and In concentrations in Si by RBS spec
tra is complicated by the overlapping of peaks from In
and As. To solve this problem, we measured RBS spec
IonBeam Synthesis of InAs Nanocrystals
in Crystalline Silicon
F. F. Komarova, O. V. Mil’chanina, L. A. Vlasukovaa, W. Weschb, 
A. F. Komarova, and A. V. Mudryic
a Belarusian State University, Minsk, 220030 Belarus
email: komarovf@bsu.by
b Friedrich Schiller University, D07743 Jena, Germany
c Scientific and Practical Materials Research Center, National Academy of Sciences of Belarus, Minsk, 220072 Belarus 
Abstract—The formation of nanodimensional InAs crystallites on Si wafers was studied by the method of
highfluence implantation of As and In ions with subsequent hightemperature treatment. It was found that
the size and depth distributions of the crystallites depend on both the implantation temperature and the
annealing conditions. A broad band in an energy range of 0.75–1.1 eV was recorded in the photolumines
cence spectra of the samples.
DOI: 10.3103/S1062873810020310
BULLETIN OF THE RUSSIAN ACADEMY OF SCIENCES: PHYSICS  Vol. 74  No. 2  2010
IONBEAM SYNTHESIS OF InAs NANOCRYSTALS IN CRYSTALLINE SILICON 253
tra at two angles of the incidence of helium ions into
the samples: 0° and 50°. The depth profiles were cal
culated by simulations of the spectra until they coin
cided completely with the experimental spectra
obtained at two angles of the incidence of helium ions
into the samples. The profiles of In and As after
implantation at room temperature are close to the cal
culated profiles. The hot conditions of implantation
lead to a broadening of the depth profiles as compared
to the calculation data, and a displacement of the
depth profiles toward the sample surface is observed.
The subsequent hightemperature annealing of the
implanted samples (for the two implantation temper
atures) results in a significant redistribution of impu
rity atoms and a decrease in its concentration. Finally,
(after heat treatment), hot implantation leads to
broader (up to 400 nm deep) depth profiles as com
pared to implantation at 25°C.
The results of the TEM studies are depicted in
Fig. 3. For the sample implanted at room temperature
with an additional implantation of hydrogen, a thin
layer of secondary defects (mostly dislocation loops) is
registered at a depth of approximately 500 nm. The
16k
0
100 200
12k
8k
4k
300 400
3×
16k
0
100 200
12k
8k
4k
300 400
3×
Yield
Channel number
(a)
(b)
Fig. 1. RBS spectra of Si samples implanted with As ions
(245 keV, 4.1 × 1016 cm–2) and In ions (350 keV, 3.7 ×
1016 cm–2) at temperatures of 25 (a) and 500°C (b) and
annealed at 900°C for 60 min. Random spectra are
depicted by open circles; spectra upon channeling, by full
circles.
6
0 100 200
4
2
300 400 500
6
0 100 200
4
2
300 400 500
7
As
In
In
As
6
0 100 200
4
2
300 400 500
In
As
Implantation
In + As, 25°С
Annealing
900°С, 60 min
Implantation
In + As, 500°С
As
In
Annealing
900°С, 60 min
As
In
Depth, nm
A
to
m
ic
 c
on
ce
n
tr
at
io
n
, 
%
 
A
to
m
ic
 c
on
ce
n
tr
at
io
n
, 
%
A
to
m
ic
 c
on
ce
n
tr
at
io
n
, 
%
(a)
(b)
(c)
Fig. 2. Simulated (SRIM 2003) (a) and calculated (RBS
spectra) depth profiles of As and In atoms in silicon
implanted at 25 (b) and 500°C (c).
254
BULLETIN OF THE RUSSIAN ACADEMY OF SCIENCES: PHYSICS  Vol. 74  No. 2  2010
KOMAROV et al.
formation of defects of this sort is characteristic of the
process of recrystallization of amorphous layers. Sep
arate inclined dislocations are observed throughout
the entire implanted layer. The irregularity (rough
ness) of the surface in comparison with the initial
wafer should be noted. This presumably may be attrib
uted to defect system transformation during annealing
and to a shift of impurities (indium) from the near
surface region. At depths from 100 to 350 nm, there
are small precipitates from 2 to 10 nm in size. This
region in the crystal corresponds to concentration
maxima in the implanted impurity profiles. A detailed
study of the structure of these inclusions according to
the technique described in [1] allowed us to identify
them as InAs nanocrystals. In the case of hot implan
tation, two spatially separated layers of secondary
defects are observed. The first defect layer containing
micropores and microtwins is localized in the thin
nearsurface region. In the deeper defect layer (400–
450 nm), separate dislocation loops are recorded. The
density of secondary defects is significantly lower than
for the samples described in [1]. Between the two
defect layers, at the sample depth of 80–350 nm, there
is a defectfree silicon region containing InAs precip
itates. Alongside the small clusters (from 2 nm), con
siderably larger ones with sizes up to 80 nm are
observed (Fig. 3e). Increasing the duration of heat
treatment up to 60 min thus leads to a reduction in the
density of secondary defects in the structure and to an
appreciable increase in the size of InAs precipitates (in
[1], the average size of precipitates was 3–6 nm for an
annealing duration of 45 min).
Figure 4 depicts the PL spectra of samples mea
sured at 4.2 K after implantation and subsequent
annealing. For the crystals implanted at 25°C, a broad
band in a range of 0.75–1.1 eV with a maximum of
0.93 eV is recorded in PH spectra. The intensity of this
band is almost five times greater for the samples with a
getter layer in comparison with the sample without
getter (curves 2 and 1 in Fig. 4a, respectively). A band
with a phononless line of 0.79 eV is observed in the
spectrum, due to the recombination of bound excitons
(a)
100
mm
(b)
1.8 nm
100
mm(c)
20 nm
(d) (e)
Fig. 3. TEM images of the crosssection of silicon samples
after implantation of In and As ions at 25 (a, c) and 500°C
(b, d, e) and hightemperature annealing.
0.7 0.8 0.9 1.0 1.1 1.2
0.7 0.8 0.9 1.0 1.1 1.2
In
te
n
si
ty
, 
ar
b.
 u
n
it
s
(a)
(b)
1
2
2
1
Photon energy, eV 
T ~ 4.2 K
T ~ 4.2 K
Fig. 4. PL spectra of silicon samples after implantation of
As+ and In+ ions at 25 (a) and 500°C (b) and hightemper
ature treatment.
BULLETIN OF THE RUSSIAN ACADEMY OF SCIENCES: PHYSICS  Vol. 74  No. 2  2010
IONBEAM SYNTHESIS OF InAs NANOCRYSTALS IN CRYSTALLINE SILICON 255
on ioninduced defects (interstitial carbon–interstitial
oxygen (Ci–Oi pairs)) [2]. For the samples implanted
at 500°С, a broad band in the range 0.75–1.1 eV with
an extended lowenergy wing is also found in the PL
spectra (curve 1 in Fig. 4b). The intensity of this band
is four times greater than that of samples implanted at
room temperature (Fig. 4a, curve 1). For purposes of
comparison, Fig. 4b depicts the PL spectrum of a sam
ple for which the implantation fluences of arsenic and
indium ions were higher by a factor of 1.5 and the
duration of annealing at 900°С was less (curve 2) as
compared to the conditions of the present experiment
[1]. We may assume from a comparison of the spectra
in Fig. 4b that the broad band in a range 0.75–1.1 eV
is a superposition of at least two PL bands with max
ima of ~0.94 and ~0.99 eV.
CONCLUSIONS
In this work, we studied the influence of impurity
(As + In) implantation temperature and regimes of
postimplantation annealing on the processes of the
ionbeam synthesis of InAs nanocrystals in silicon. It
was found that a decrease in the fluence of ions and a
reduction in the duration of heat treatment allow us to
reduce the level of damage in an implanted layer. An
increase in the duration of annealing, however, leads
also to an increase in the size of formed InAs nanoc
rystals (up to 80 nm). For all of the samples, the PL
spectra exhibit a broad band in the spectral range
0.75–1.1 eV. Application of an additional implanta
tion of hydrogen ions for the formation of a gettering
layer in the process of postimplantation annealing
makes it possible to significantly increase the intensity
of the given PL band.
ACKNOWLEDGMENTS
This work was supported in part by the Belarusian
Republican Foundation for Fundamental Research,
projects no. T08R–175 and F08–150.
REFERENCES
1. Komarov, F., Vlasukova, L., Wesch, W., et al., Nucl.
Instr. and Meth. B, 2008, vol. 266, p. 3557.
2. Trombetta, J.M. and Watkins, G.D., Appl. Phys. Lett.,
1987, vol. 51, p. 1103.


Ion Beam Synthesis of InAs Nanocrystals in Crystalline Silicon

http://elib.bsu.by/bitstream/123456789/20405/1/BRAS252.pdf

Ion Beam Synthesis of InAs Nanocrystals in Crystalline Silicon

Abstract

Similar works

Full text

Available Versions

Электронная библиотека БГУ