Composition and structural perfection of (AIII,Mn)BV and MnBV (A = Ga, In; B = Sb, As, P) nanolayers

Article abstract of DOI:10.1134/S0020168512050044

We have determined the elemental composition of laser-deposited (Ga,Mn)Sb, (In,Mn)As, MnP, MnAs, and MnSb layers. The InMnAs layers were not single-phase and contained MnAs clusters. Active Ga and Mn diffusion to the substrate and arsenic diffusion from the substrate during the GaMnSb growth process is accompanied by the formation of a GaMnAs intermediate layer. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0020168512050044

ISSN 0020ꢀ1685, Inorganic Materials, 2012, Vol. 48, No. 6, pp. 553–558. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.S. Dunaev, B.N. Zvonkov, Yu.A. Danilov, O.V. Vikhrova, Yu.N. Drozdov, M.N. Drozdov, A.I. Suchkov, 2012, published in Neorganicheskie Materialy,
2012, Vol. 48, No. 6, pp. 643–648.
III
V
Composition and Structural Perfection of (A ,Mn)B
V
and MnB (A = Ga, In; B = Sb, As, P) Nanolayers
V. S. Dunaev , B. N. Zvonkov , Yu. A. Danilov , O. V. Vikhrova , Yu. N. Drozdov ,
a
b
b
b
c
c
d
M. N. Drozdov , and A. I. Suchkov
a
Lobachevsky State University, pr. Gagarina 23, Nizhni Novgorod, 603950 Russia
Research Institute of Physics and Technology, Lobachevsky State University,
b
pr. Gagarina 23/3, Nizhni Novgorod, 603950 Russia
Institute for Physics of Microstructures, Russian Academy of Sciences, ul. Ulyanova 46, Nizhni Novgorod, 603950 Russia
c
d
Institute of Chemistry of HighꢀPurity Substances, Russian Academy of Sciences,
ul. Tropinina 49, Nizhni Novgorod, 603950 Russia
eꢀmail: danilov@nifti.unn.ru
Received November 23, 2011
Abstract—We have determined the elemental composition of laserꢀdeposited (Ga,Mn)Sb, (In,Mn)As,
MnP, MnAs, and MnSb layers. The InMnAs layers were not singleꢀphase and contained MnAs clusters.
Active Ga and Mn diffusion to the substrate and arsenic diffusion from the substrate during the GaMnSb
growth process is accompanied by the formation of a GaMnAs intermediate layer.
DOI: 10.1134/S0020168512050044
INTRODUCTION
cient detail. One major problem is the lack of data on
the composition–depth profile in such structures in
relation to the substrate material, deposition temperaꢀ
ture, and impurity concentration. Other important
issues are structural perfection and the effect of interꢀ
diffusion from the substrate into the layer and from the
layer into the substrate during the growth process on
Recent years have seen increasing interest in spinꢀ
tronics because the use of the spin, a fundamental
property of electrons, along with their charge, is
expected to open up new possibilities for semiconducꢀ
tor devices and logic circuits.
A key requirement for spintronic devices is efficient the properties of the material.
injection of spinꢀpolarized carriers into their active
In this paper, we report the elemental composition
region. Spin injection from a ferromagnetic metal into
a “conventional,” nonmagnetic semiconductor is an
attractive approach because a number of ferromagꢀ
netic metals (for example, Fe and Co) possess a suffiꢀ
ciently high Curie temperature, but they have one seriꢀ
ous drawback: as a result of the conductivity mismatch
between the metallic spin injector and semiconductor
channel, the spin injection efficiency is typically no
higher than 1% [1].
of layers of the (Ga,Mn)Sb and (In,Mn)As semiconꢀ
ductors and MnP, MnAs, and MnSb magnetic halfꢀ
metals produced by laser deposition in a horizontal
quartz reactor.
EXPERIMENTAL
(
In,Mn)As and MnBV (B = P, As, Sb) layers were
grown on ꢀGaAs(100) substrates at substrate temperꢀ
atures in the range tg = 300–450 , and (Ga,Mn)Sb
layers were grown on ꢀGaAs(100) and ꢀInAs(100)
substrates at tg = 400 . Metallic Mn and undoped
semiconductor (InAs or GaSb) targets were sputtered
alternately by a 1.06ꢀ m pulsed Nd:YAG laser. The
i
The use of magnetic semiconductors allows semiꢀ
conducting properties to be combined with properties
of ferromagnetic materials (for example, spin injecꢀ
°C
i
p
°
C
tion across a
p–n
junction). Most interest has centered
on soꢀcalled diluted magnetic semiconductors of the
µ
III
V
(
А ,Mn)В type containing up to 5–10 at % Mn [2],
sputtering process was run in a hydrogen + arsine flow
in the case of (In,Mn)As and in flowing hydrogen in
the case of (Ga,Mn)Sb. The process parameter that
determined the Mn content (YMn) of the (Ga,Mn)Sb
and (In,Mn)As layers was the ratio of the sputtering
times of the metallic (Mn) and semiconductor (s) tarꢀ
which have a rather high Curie temperature (TC) [3].
Also attractive in this context are the binary comꢀ
pounds MnBV, which have high Curie temperatures
(
TC = 298 K for MnP, 318 K for MnAs, and 587 K for
MnSb [4]).
There are a number of physics and technology gets:
τ
Mn/(
τ
+
τ
s). In addition, MnSb layers were
grown through alternating laser sputtering of Mn and
structures, which have not yet been studied in suffiꢀ Sb metallic targets. The MnP and MnAs layers were
Mn
III
V
issues pertaining to the formation of (А ,Mn)B
553

5
54
Table 1. Xꢀray microanalysis results for MnB magnetic halfꢀmetals
Material Preparation procedure
MnSb/GaAs Alternating sputtering of Mn and Sb,
DUNAEV et al.
V
Atomic percent
tg, °C
d, nm
Mn
BV
τ
Mn/
τ
= 5
300
350
370
110
100
320
71
33
45
29
67
55
Sb
MnP/GaAs
MnAs/InP
Mn sputtering in flowing phosphine
Mn sputtering in flowing arsine
produced through reactive laser sputtering of mangaꢀ loss in the gas phase. Xꢀray diffraction patterns of the
nese in flowing phosphine and arsine, respectively.
The structural perfection of the layers was assessed
by doubleꢀcrystal Xꢀray diffraction on a DRONꢀ4 difꢀ
layers showed, in addition to a reflection from the subꢀ
strate, 002 GaAs, a rather strong peak at 29.3°,
which could be indexed as 200 GaSb. The full width at
half maximum of the latter peak was on the order of
2θ Ӎ
fractometer (Ge (400) monochromator, CuKα1 radiaꢀ
tion). Elemental concentration profiles were obtained
using secondary ion mass spectrometry (SIMS) on a
TOF.SIMSꢀ5 system (dual beam principle) equipped
with a timeꢀofꢀflight mass analyzer. Composition–
depth profiles across the (In,Mn)As structures were
0.5° at tg = 300°C. It should be taken into account that
the lattice parameter of (Ga,Mn)Sb decreases slightly
with increasing manganese concentration [5]. It is,
therefore, reasonable to assume that the peak in quesꢀ
tion is due to a (Ga,Mn)Sb layer with a low Mn conꢀ
centration epitaxially grown on the GaAs (100) subꢀ
strate. As the deposition temperature decreases to
+
obtained using etching with O2 ions (energies of up to
1
keV), and those of the (Ga,Mn)Sb structures were 200
°С, the intensity of the peak at
2
θ
29.3°
+
obtained using etching with Cs ions. The probe beam decreases considerably, and its full width at half maxiꢀ
+
mum increases (up to 5.5°). It seems likely that interꢀ
diffusion of the components of the Mn Sb x/GaAs
was a nanosecond (1 ns) 25ꢀkeV Bi ion pulse. In the
+
+
+
+
former instance, In , Mn , As , and Ga secondary
x
1 –
layer and substrate produces a (Ga,Mn)Sb transition
layer at the Mn Sb x/GaAs interface. In addition, the
positive ions were recorded. In the case of the
Ga,Mn)Sb layers, we recorded MnSb–
,
GaSb
–
,
(
x
1 –
MnAs , and GaAs– negative cluster ions. The paramꢀ
–
Xꢀray diffraction pattern showed rather broad, weaker
peaks, in particular, one at
attributable to MnSb.
2θ ≈ 43.6°, which were
eters of the craters (depth, lateral dimensions, and surꢀ
face roughness) were measured with a Talysurf CCI
V
The composition of the MnP layers produced by
laserꢀsputtering Mn in flowing PH3 was found to be a
weak function of tg: the manganese content increased
2000 system. The elemental composition of the MnB
films was determined by Xꢀray microanalysis on an
SEMꢀ515 scanning electron microscope equipped
with an EDAX 9900 energy dispersive spectrometer
system. The key features of this method (escape depth
from 31.4% at a growth temperature of 300
°С to
3
5.5% at 450 . Therefore, the layer contained
°С
approximately one manganese atom for two phosphoꢀ
rus atoms. We have found no data on a compound of
composition MnP2 or its magnetic properties in the
literature.
of characteristic Xꢀrays, 1 m or more; thickness of
µ
the layer to be analyzed, 100 nm) impose additional
limitations on the structures under consideration.
Layer/substrate combinations were selected so that the
layer and substrate differed completely in elemental
The MnAs layer grown by reactive laser sputtering
composition (for example, MnAs/InP). Relative conꢀ of Mn in flowing AsH3 at 370
°С
had a nearly stoichiꢀ
centrations were determined by standardless analysis ometric composition, with a slight arsenic enrichment
(
with an accuracy on the order of 10–15%).
(Table 1).
Taking into account the key features of the deposiꢀ
tion process, namely, the fact that the MnAs and MnP
layers were produced by laserꢀsputtering metallic Mn
RESULTS AND DISCUSSION
Using Xꢀray microanalysis, we determined the eleꢀ in a gas flow, we conclude that the composition of
mental composition of the MnBV layers. The results these layers was governed by the chemical reaction
are presented in Table 1.
between Mn and the Group V element (arsenic or
The MnSb layers were grown at ratios of the sputꢀ phosphorus), in contrast to MnSb, whose composiꢀ
tering times of the Mn and Sb targets in the range tion was determined by the sputtering times of the tarꢀ
τ
Mn/τ
Sb
= 2.5–10 because the sputtering rate of metalꢀ gets.
lic antimony considerably exceeded that of metallic
Whereas Xꢀray microanalysis provides information
manganese. It was found, however, that the Mn conꢀ about the overall content of a particular element in an
tent of the deposit was 69—87 at % and was a weak entire layer, SIMS can be used to obtain composiꢀ
function of substrate temperature in the range 200– tion–depth profiles of structures. Unfortunately, the
300°С. Clearly, we failed to take into account the Sb TOF.SIMSꢀ5 instrument has no absolute calibration
INORGANIC MATERIALS Vol. 48
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2012

III
V
V
COMPOSITION AND STRUCTURAL PERFECTION OF (A ,Mn)B AND MnB
555
1
1
1
04
5
4
03
3
2
1
8
6
4
2
02
0
0.1 0.2 0.3
YMn
0
50
100
150
200
x, nm
Fig. 1. Mn concentration profiles across (In,Mn)As layers grown at tg = 320
) 0.26. Inset: overall Mn content as a function of YMn
°C
:
YMn = (1) 0.05, (2) 0.09, (3) 0.16, (4) 0.20,
(5
.
for elemental analysis, so only relative compositional
A comparative analysis of Xꢀray diffraction data for
changes with depth can be assessed. Figure 1 shows the the InMnAs and undoped InAs layers showed that the
Mn concentration profiles across the (In,Mn)As layꢀ Xꢀray diffraction patterns of the InMnAs layers with
ers. The process parameter YMn was varied from 0.05 to high YMn values contained, in addition to the 200 peak
0
.26. In all cases, we observed a slight Mn enrichment from the GaAs substrate and the 002 peak from the
in the surface layer. At a low Mn content (YMn = 0.05), InAs layer at
= 31.6° and 29.5°, respectively, peaks
the Mn distribution is uniform over most of the thickꢀ close in angular position to peaks from the hexagonal
ness of the layer. For YMn 0.09, the depth profiles
have a wellꢀdefined maximum (xmax 75 nm at YMn
.09). With increasing dopant concentration, the
maximum shifts toward the substrate (xmax 135 nm at
2
θ
≥
phase MnAs (10
1 2
2 peak at 42.3° and 11 0 peak at
Ӎ
=
48.9°). Given that the peak from the layer was rather
0
narrow, we conclude that the InMnAs layers were sinꢀ
gleꢀcrystalline but not singleꢀphase.
Ӎ
YMn = 0.26), which is caused by the increase in the
thickness of the layer and the broadening of the interꢀ
face as a result of the interdiffusion of the components
of the layer and substrate during the growth process.
One possible cause of the maximum in the manganese
concentration profiles is the formation of an addiꢀ
Consider now the SIMS depth profiling results for
structures with GaMnSb layers. The growth condiꢀ
tions of the structures are summarized in Table 2. The
variable parameters were the manganese content
(
from 0 to YMn = 0.33) and growth temperature (300
). SIMS depth profiles for four samples
tional manganeseꢀcontaining phase (for example, and 400°С
MnAs clusters). MnAs clusters on the order of 20 nm (undoped and manganeseꢀdoped, grown on two types
in size were found by Ganshina et al. [6] using transꢀ of substrates) are presented in Figs. 2 (
mission electron microscopy in a layer grown near an
iꢀGaAs subꢀ
InMnAs/GaAs interface for structures from a series of
samples studied by us.
Table 2. Growth parameters of GaMnSb layers
Samꢀ
ple
YMn
=
Gaseous enꢀ
Mn) vironment
The inset in Fig. 1 illustrates the effect of the proꢀ
cess parameter YMn on the overall Mn content of the
layers (measured in counts × centimeter). The relaꢀ
tionship between the two parameters is seen to be
Substrate tg, °C
τ
Mn/(
τ
+
τ
GaSb
I
GaAs
GaAs
GaAs
GaAs
GaAs
InAs
400
400
300
300
400
400
400
0
H2
II
0.06
0.33
0.33
0.33
0
H2
almost linear up to the highest value of YMn
.
III
IV
V
H2
In addition, our results demonstrate that increasing
the Mn content of InAs layers increases the thickness of
the transition layer (from 13 nm at YMn = 0 to 70 nm at
YMn = 0.26), which is due to Ga diffusion from the
GaAs substrate to the layer. For this reason, a layer of an
InGaMnAs solid solution may grow near the interface.
H + AsH
2
3
H2
VI
VII
H2
InAs
0.33
H2
INORGANIC MATERIALS Vol. 48
No. 6 2012

556
DUNAEV et al.
(а)
1
03
GaSb
As
Sb
1
02
1
01
0
50
100
x, nm
(
b)
1
04
GaSb
As
Sb
1
03
MnSb
MnAs
GaMnAs
1
02
1
01
0
100
200
x, nm
Fig. 2. SIMS depth profiles for structures (a) I and (b) II containing a GaMnSb layer (
.06, respectively.
iꢀGaAs substrate) with YMn = 0 and YMn =
0
strate) and 3 (pꢀInAs substrate). Analysis of the eleꢀ from the substrate. Most likely, Mn diffusion into the
mental concentration profiles across the (Ga,Mn)Sb substrate during the growth process initiates arsenic
layers revealed considerable arsenic diffusion from the diffusion into the layer (arsenic is then incorporated
substrate to the layer at nonzero Mn concentrations on into the Sb site), leading to the formation of a thin
( 50–100 nm in thickness) Ga1 – Mn Sb yAs layer
x Ӎ
200 near the nominal GaMnAs/GaAs interface.
It is also worth noting active Ga diffusion into
pꢀInAs substrates, which broadens the transition layer
of the MnAs– and GaMnAs cluster ions with identiꢀ from approximately 40 to 80 nm (Fig. 3).
ꢀ
both the InAs and GaAs substrates. In addition, in the
x x 1 – y
layers with YMn
≠
0
near the interface at
ꢀGaAs, Fig. 2) and 125 nm
ꢀInAs, Fig. 3) we identified peaks
(
GaMnSb layers on
i
(GaMnSb layers on
p
–
cal concentration profiles. Moreover, the MnSb conꢀ
centration profile and arsenic diffusion indicate that diffraction. The results (Fig. 4) demonstrate that the
The GaMnSb layers were characterized by Xꢀray
the composition of the layer depends on the distance diffraction patterns of samples IV and V contain, in
INORGANIC MATERIALS Vol. 48
No. 6
2012

III
V
V
COMPOSITION AND STRUCTURAL PERFECTION OF (A ,Mn)B AND MnB
557
(
а)
1
1
1
03
02
01
As
In
GaSb
Sb
GaAs
0
100
200
b)
300
x
, nm
(
GaSb
As
03
1
In
MnSb
Sb
GaMnAs
MnAs
1
02
1
01
0
100
200
300 x, nm
Fig. 3. SIMS depth profiles for structures (a) VI and (b) VII containing a GaMnSb layer (
andYMn = 0.33, respectively.
pꢀInAs substrate) with YMn = 0
addition to major peaks (from the GaAs substrate and
GaSb layer at
2 = 31.6° and 29.4°, respectively),
θ
extra peaks. In the Xꢀray diffraction pattern of sample
IV, such peaks are attributable to polycrystalline GaAs
4
(
4
27.3°, 111; 45.5°, 220) and MnAs (40.4°, near 112;
2.5°, 202 and/or 211). The reason for the formation
of MnAs as an additional phase is that the layers were
grown in an AsH atmosphere. The broad peak at 2
3
2
θ
=
3
43.4° in the Xꢀray diffraction pattern of sample V is
1
Fig. 4. Xꢀray diffraction patterns of GaMnSb layers: samꢀ
ples ( ) I, ( ) V, ( ) IV, and ( ) III (see Table 2).
22 24 26 28 30 32 34 36 38 40 42 44 46
, deg
1
2
3
4
2
θ
INORGANIC MATERIALS Vol. 48
No. 6 2012

558
DUNAEV et al.
attributable to metallic Mn. The GaMnSb structures the Scientific Potential of Higher Education Instituꢀ
characterized by SIMS were grown in a hydrogen tions, project nos. 2.2.2.2/4297ꢀ11107 and
–
atmosphere, so the MnAs secondary cluster ions 2.1.1/2833ꢀ12029; and contract no. 02.740.11.0672),
identified (Figs. 2, 3) were most likely unrelated to the the RF President’s Grants Council (Support to
formation of the MnAs phase and originated from the Young Scientists of Russia Program, grant
transition layer.
no. 16.120.11.5359ꢀMK), and the Presidium of the
Russian Academy of Sciences.
CONCLUSIONS
REFERENCES
Reactive laser deposition allows one to produce
MnBV layers whose composition is governed by the
chemical reaction between their components and,
possibly, by diffusion of atoms from the substrate durꢀ
ing the growth process. At high magnetic impurity
concentrations, the Mn concentration profile across
epitaxial InMnAs layers is nonuniform, which seems
to be caused by the formation of MnAs clusters during
the growth process. The GaMnSb layers are not sinꢀ
gleꢀphase, which is most likely due to arsenic diffusion
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. Danilov, Yu.A., Kudrin, A.V., Vikhrova, O.V., et al.,
Ferromagnetic Semiconductor InMnAs Layers Grown
by Pulsed Laser Deposition on GaAs, J. Phys. D: Appl.
Phys., 2009, vol. 42, paper 035 006.
(
in the presence of Mn) from the substrate to the layer
on both ꢀGaAs and ꢀInAs substrates and to Ga diffuꢀ
sion from the layer to the ꢀInAs substrate.
i
p
4.
Tablitsy fizicheskikh velichin. Spravochnik (Tables of
Physical Quantities: A Handbook), Kikoin, I.K., Ed.,
Moscow: Atomizdat, 1976, p. 526.
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Compd.,1994, vol. 205, pp. 81–85.
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vol. 22, paper 396 002.
ACKNOWLEDGMENTS
This work was supported in part by the Russian
Foundation for Basic Research (grant nos. 10ꢀ02ꢀ
0739 and 11ꢀ02ꢀ00645), the RF Ministry of Educaꢀ
tion and Science (federal targeted program Scientists
and Teachers of Innovative Russia, 2009–2013; analytꢀ
ical departmental targeted program Development of
0
6
INORGANIC MATERIALS Vol. 48
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2012