Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb>
The influence of isovalent impurity of Si on the kinetics of electron processes in n-Ge <Sb> single crystals has been investigated. It has been shown that in the region of predominant impurity scattering (at Т = 77.4 K), the presence of isovalent impurity significantly reduces the mobility...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2014
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| Cite this: | Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> / G.P. Gaidar // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 1. — С. 25-28. — Бібліогр.: 14 назв. — англ. |
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nasplib_isofts_kiev_ua-123456789-1183552025-02-23T18:08:29Z Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> Gaidar, G.P. The influence of isovalent impurity of Si on the kinetics of electron processes in n-Ge <Sb> single crystals has been investigated. It has been shown that in the region of predominant impurity scattering (at Т = 77.4 K), the presence of isovalent impurity significantly reduces the mobility of charge carriers and changes the sign of inequality ne₃₀₀k / ne₇₇.₄k > 1 characteristic of n-Ge <Sb> single crystals to the opposite one. It has found that in n-Ge <Sb> samples irradiated by y-rays (⁶⁰Co) with the dose 1.23*10⁸ R, the charge carrier mobility has low radiation stability and decreases with increasing the magnetic field, while remaining practically unchanged in the region of the intermediate Н values. 2014 Article Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> / G.P. Gaidar // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 1. — С. 25-28. — Бібліогр.: 14 назв. — англ. 1560-8034 PACS 61.82.Fk, 61.72.uf, 61.72.S-, 72.20.-i https://nasplib.isofts.kiev.ua/handle/123456789/118355 en Semiconductor Physics Quantum Electronics & Optoelectronics application/pdf Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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The influence of isovalent impurity of Si on the kinetics of electron processes
in n-Ge <Sb> single crystals has been investigated. It has been shown that in the region of
predominant impurity scattering (at Т = 77.4 K), the presence of isovalent impurity
significantly reduces the mobility of charge carriers and changes the sign of inequality
ne₃₀₀k / ne₇₇.₄k > 1 characteristic of n-Ge <Sb> single crystals to the opposite one. It has
found that in n-Ge <Sb> samples irradiated by y-rays (⁶⁰Co) with the dose 1.23*10⁸ R, the
charge carrier mobility has low radiation stability and decreases with increasing the
magnetic field, while remaining practically unchanged in the region of the intermediate
Н values. |
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Article |
| author |
Gaidar, G.P. |
| spellingShingle |
Gaidar, G.P. Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Gaidar, G.P. |
| author_sort |
Gaidar, G.P. |
| title |
Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> |
| title_short |
Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> |
| title_full |
Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> |
| title_fullStr |
Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> |
| title_full_unstemmed |
Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> |
| title_sort |
investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰co) on electrophysical parameters of n-ge <sb> |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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2014 |
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https://nasplib.isofts.kiev.ua/handle/123456789/118355 |
| citation_txt |
Investigation of the influence of isovalent impurity of silicon and y-irradiation (⁶⁰Co) on electrophysical parameters of n-Ge <Sb> / G.P. Gaidar // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 1. — С. 25-28. — Бібліогр.: 14 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
AT gaidargp investigationoftheinfluenceofisovalentimpurityofsiliconandyirradiation60coonelectrophysicalparametersofngesb |
| first_indexed |
2025-11-24T06:14:47Z |
| last_indexed |
2025-11-24T06:14:47Z |
| _version_ |
1849651245672824832 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 1. P. 25-28.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
25
PACS 61.82.Fk, 61.72.uf, 61.72.S-, 72.20.-i
Investigation of the influence of isovalent impurity of silicon
and -irradiation (60Co) on electrophysical parameters of n-Ge Sb
G.P. Gaidar
Institute for Nuclear Research, National Academy of Sciences of Ukraine,
47, prospect Nauky, 03680 Kyiv, Ukraine; e-mail: gaydar@kinr.kiev.ua
Abstract. The influence of isovalent impurity of Si on the kinetics of electron processes
in n-Ge Sb single crystals has been investigated. It has been shown that in the region of
predominant impurity scattering (at Т 77.4 K), the presence of isovalent impurity
significantly reduces the mobility of charge carriers and changes the sign of inequality
1/
K4.77K300
ee nn characteristic of n-Ge Sb single crystals to the opposite one. It has
found that in n-Ge Sb samples irradiated by -rays (60Co) with the dose 1.23108 R, the
charge carrier mobility has low radiation stability and decreases with increasing the
magnetic field, while remaining practically unchanged in the region of the intermediate
Н values.
Keywords: germanium, isovalent impurity, silicon, γ-irradiation, Hall effect, charge
carrier mobility, electron concentration.
Manuscript received 11.11.13; revised version received 26.12.13; accepted for
publication 20.03.14; published online 31.03.14.
1. Introduction
For most of problems of the applied character, it is
important not only a high degree of homogeneity of the
crystal, but what kind and state of impurity are available
in its bulk, since all this, ultimately, influences the
concentration of charge carriers and their mobility.
These problems can be solved by investigating crystals
in various aspects:
a) by direct studying the influence of certain chemical
elements on their electrical properties;
b) by revealing features of the influence of
semiconductor compensating impurities on these
properties;
c) by analyzing various schemes of complexing and its
consequences to which it leads in the crystal bulk.
Concerning electrically active impurities, at least,
basic properties of almost every element leading to
formation of singly and multiply charged centers in Ge
and Si were studied. More difficult is the situation with
the so-called electrically passive impurities of different
elements in these crystals. When considering that
according to the data of mass-spectroscopic analysis, the
content of oxygen in Ge is about 21018 cm–3, and the
contents of hydrogen and carbon in it are about the same
[1], then, naturally, a question arises, what features of
charge carrier scattering, for example, may be associated
with these impurities, since in other experiments (e.g.
when studying absorption of infrared radiation [2]), the
presence of these impurities in the crystal bulk is easily
singled out. The question concerning the interaction of
these impurities with other impurities that are in the n-
Ge crystal bulk and resulting formation of various
complexes is of particular interest. For example, the
impurity atoms of Si in Ge, which are isovalent
impurities, may affect transport phenomena occurring in
germanium not only as electrically neutral elementary
scatterers, but also in the form of neutral or charged
complexes. These complexes may arise during
interaction of silicon atoms with the atoms of electrically
neutral or active impurities that are in the crystal bulk.
This fact combined with very little data in the literature
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 1. P. 25-28.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
26
Table. Electrophysical parameters of n-Ge single crystals for unitary (Ge Sb) and double doping (Ge Sb+Si).
Т 300 K Т 77.4 K
D
op
an
t
N
um
be
r
of
n-
G
e
sa
m
pl
e
R,
сm3/Coul
ne,
сm-3
,
сm2/Vs
R,
сm3/Coul
ne,
сm–3
,
сm2/Vs
K4.77
K300
e
e
n
n
r
1 5.09105 1.231014 2960 4.70105 1.331014 23100 0.925
2 3.70104 1.691014 2680 3.65104 1.761014 19600 0.960Sb+Si
3 2.86104 2.181014 3200 2.54104 2.461014 20500 0.886
1' 9.04105 6.921013 3070 1.08105 5.781013 29200 1.197
2' 8.09104 7.741013 3050 9.70104 6.901013 28300 1.122Sb
3' 6.90104 9.081013 2560 8.15104 7.681013 27000 1.182
relative to the problem of complex formation in Ge (the
situation with Si containing isovalent impurity of Ge is
somewhat better [3-6]) important in general for physics
and chemistry of solids have prompted to undertake
studying the influence of Si isovalent impurities on the
Hall mobility of charge carriers in n – Ge.
Back in the sufficiently early studies (see, e.g. [7]),
it was shown that Si is an electrically neutral impurity
relative to Ge, i.e., its atoms found in the bulk of Ge do
not lead to appearance of additional charge carriers.
However, it can be assumed that the impurity atoms of
Si (even in the case of its electrical neutrality) influence
on the mobility of charge carriers in the area of impurity
scattering. The aim of this study was to experimental
determine contribution of this scattering in a resultant
value of the mobility. For this goal, comparative
experiments using the reference samples of Ge doped
with Sb and samples of Ge doped with Sb and Si were
carried out.
The scientific literature, as far as it is known [8-12],
is very poor in sources related to the study of the kinetics
of the electron gas in crystals grown at combined doping
(i.e., when doping more than one impurity).
2. Results and discussion
To study the influence of Si isovalent impurity on
electrophysical properties of n-Ge doped with an
electrically-active impurity of antimony (Sb), ingots, some
of which were doped only with Sb impurity (unitary
doping) and others besides the Sb impurity were doped
with silicon with approximately the same concentration
(double or combined doping), were used. From these
ingots, two groups of samples (three samples in each
group) were prepared. The obtained samples possess
suitable sizes and shapes for measurements of the
resistivity and Hall effect both at room temperature and at
liquid nitrogen one (Fig. 1). The samples in both cases
were cut from ingots in the direction of their growth,
which coincided with the crystallographic orientation
[110]. The magnetic field oriented in the crystallographic
direction H
|| [001] was applied perpendicular to the
lateral surface of the samples. All the measurements were
performed at H = 2340 Oe.
Before soldering current contacts and contacts to
the measuring probes, the samples were polished and
etched for about 2 min in a boiling solution of 30 %
hydrogen peroxide, and then they were washed with
distilled water. After the contacts were soldered using
pure tin (Sn), the samples were etched again. Before the
measurements, the ohmic regime of current contacts was
tested at the current values that by several times
exceeded the values used in our experiments.
The results of the measurements carried out using
the samples of germanium both at 300 K and at 77.4 K
are presented in Table.
The results obtained by the experiments (Table)
show that the insertion of isovalent impurity of Si in Ge
crystals (even more heavily doped with antimony than the
1'–3' samples) leads to a significant change in
electrophysical properties of these crystals, which finds its
expression in a number of features. For example, the sign
of inequality 1/
K4.77K300
ee nn , which is typical for the
initial samples (i.e., for n-Ge Sb), changes to the
opposite one when introducing isovalent silicon atoms
into the germanium crystal in addition to doped Sb atoms.
Fig. 1. External view, shape and dimensions (in millimeters) of
investigated n-Ge samples.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 1. P. 25-28.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
27
Table shows that at dominant scattering by the
lattice vibrations (i.e., at 300 K), in the samples of
unitary and double doping, the values of mobility 300 K
are conventional for n-Ge with the concentration of
charge carriers 1013…1014 cm–3 and are about
2700...3000 сm2/Vs. However, in the region of
predominant impurity scattering (i.e., at 77.4 K), in the
crystals of double doping (n-Ge Sb+Si), values of the
charge carrier mobility 77.4 K are considerably lower
than those in the samples of unitary doping. Thus, the
isovalent impurity of Si atoms, being electrically
passive, significantly reduces the mobility of charge
carriers in Ge crystals, doped with electrically active
impurity of Sb as a consequence of manifestation of the
additional scattering of charge carriers by neutral centers
[13]. This result may be caused by some difference in
the tetrahedral radii of Si and Ge (rSi = 1.17 Å;
rGe = 1.22 Å) and, therefore, the emergence of local
internal stresses of the lattice around Si atoms. It can
also be a manifestation of imperfections of the Ge lattice
doped with Si, which is caused, in turn, by non-
uniformity in distribution of Si impurity in the bulk of
the studied crystals.
The values of the mobility of charge carriers in the
samples of double doping were not only smaller than the
values 77.4 K, typical for samples of unitary doping, but
they were also less sensitive (by approximately
1.3 times) to the concentration of dopant in the bulk of
the samples. This is clear from the fact that, at the
temperature 77.4 K, an increase of the concentration of
dopant ne in n-Ge Sb crystals by 33 % results in a
decrease of the charge carrier mobility in these crystals
by 8 %, while in the crystals of double doping (n-
Ge Sb+Si), an increase of the concentration of
electrically active impurity almost twice (or, more
precisely, by 85 %) provides a reduce of the mobility
only by 13 %.
0 2 4 6 8 10 12 14 16 18 20 22 24
0.7
0.8
0.9
1.0
1.1
H, kOe
T
T
R
H
/
R
0
1
2
3
4
Fig. 2. Dependences RH/R0 = f(H) obtained in the experiments
with n-Ge crystals doped with Si at Т 300 K (curves 1 and 2)
and at Т 77.4 K (curves 3 and 4). Curves 1 and 3 for the
sample 2 ( 300 K = 11.8 Ohmcm), curves 2 and 4 for the
sample 3 ( 300 K = 7.6 Ohmcm) (see Table).
103 104 105
10000
15000
20000
25000
H, Oe
, с
m
2 /V
s
1
2
Fig. 3. Dependences = (Н) of n-Ge Sb crystals before (1)
and after (2) -irradiation (60Со) with the dose 1.23108 R. The
current and the magnetic field were directed as follows:
J
|| [110], H
|| [001].
The fact that well-known literature lacks data on the
dependence of the Hall coefficient on the magnetic field
value in Ge doped with Si causes not only a technical
difficulty in the processing of Hall data, but also a
substantial obstacle in obtaining unambiguous results for
the Hall mobility of charge carriers in these crystals. In
relation with it, the measurements of the dependence of
the Hall coefficient on the magnetic field value in Ge
samples doped with Sb and Si were carried out.
The results of these experiments fulfilled both at
room temperature and at 77.4 K (Fig. 2), in fact, are
typical for n-Ge (free from the Si impurities), which was
studied in similar conditions [14].
In samples prepared from the ingot of unitary
doping n-Ge Sb (with antimony impurity doped in melt
NSb = ne = 1.21014 cm–3), in which the concentration of
atomically dispersed oxygen (determined by IR-
absorption spectra) was 1.21017 cm–3, the study of the
dependence of Hall mobility on the magnetic field value
before (initial three samples) and after -irradiation
(60Co) with the dose 1.23108 R was carried out. The
vectors of the current J
and magnetic field H
in the
samples were directed as follows: J
|| [110], H
|| [001].
The dependences of the mobility of charge carriers
on the magnetic field intensity in n-Ge Sb crystals
before and after -irradiation are presented in Fig. 3.
Fig. 3 shows that the mobility under the influence of
-irradiation significantly changed only in weak and
strong magnetic fields H, while in the intermediate fields
this parameter (with respect to the used dose) was almost
unchanged. However, the decrease in the carrier mobility
with increasing the magnetic field in the samples before
and after -irradiation had progressive character.
Thus, from the results of our measurements, it can
be concluded that in the initial samples Ge Sb of n-type
with atomically dispersed (electrically neutral) oxygen
impurity, the mobility of charge carriers has low
radiation resistance (mobility decreases under the
influence of γ-irradiation).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 1. P. 25-28.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
28
3. Conclusions
In this paper, the influence of Si isovalent impurity on
the Hall effect and electrical conduction in n-Ge single
crystals doped with electrically active impurity of Sb has
been investigated. It has been shown that mainly in the
field of impurity scattering (at Т 77.4 K), the presence
of electrically passive impurity of silicon in the
germanium bulk significantly reduces the mobility of
charge carriers, which is, probably, the result of a
manifestation of both additional carrier scattering by
neutral centers and changes in scattering caused by
lattice vibrations owing to violation of its structure as a
result of some difference in the covalent radii of matrix
atoms (Ge) and isovalent impurity (Si).
It has been found that in the crystals of double
doping (n-Ge Sb+Si), the sign of inequality
1/
K4.77K300
ee nn characteristic of n-Ge Sb single
crystal changes to the opposite one.
It has been found that in the unitary doped n-
Ge Sb samples irradiated by γ-quanta (60Со) with the
dose 1.23108 R, the mobility of charge carriers has low
radiation stability, and it decreases with increasing the
magnetic field value. The changes are more significant
in weak and strong magnetic fields H, while for the
intermediate H values this parameter remains practically
unchanged.
References
1. B.I. Boltaks, Diffusion and Point Defects in
Semiconductors. Nauka, Leningrad, 1972 (in
Russian).
2. А.А. Groza, P.G. Litovchenko, М.І. Starchik, The
Effects of Radiation in the Infrared Absorption and
Structure of Silicon. Naukova Dumka, Kiev, 2006
(in Ukrainian).
3. L.I. Khirunenko, V.I. Shakhovtsov, V.V. Shumov,
The radiation defect formation in Ge-doped silicon
under low-temperature irradiation // Fizika i
tekhnika poluprovodnikov, 32 (2), p. 132-134
(1998) (in Russian).
4. C.V. Budtz-Jorgensen, P. Kringhoj, A.N. Larsen,
N.V. Abrosimov, Deep-level transient spectroscopy
of the Ge-vacancy pair in Ge-doped n-type silicon
// Phys. Rev. B, 58 (3), р. 1110-1113 (1998).
5. Yu.V. Pomozov, M.G. Sosnin, L.I. Khirunenko,
V.I. Yashnik, N.V. Abrosimov, W. Shroder,
M. Hohne, Oxygen-related radiation defects in
Si1–xGex // Fizika i tekhnika poluprovodnikov
34 (9), p. 1030-1034 (2000), in Russian.
6. L.I. Khirunenko, V.I. Shakhovtsov, V.K. Shinkarenko,
L.I. Shpinar, I.I. Yaskovets, Characteristic
properties of radiation-induced defect formation in
crystals SiGe // Fizika i tekhnika polu-
provodnikov, 21 (3), p. 562-565 (1987), in Russian.
7. N.A. Gopiunova, Chemistry of Diamond-like
Semiconductors. Leningrad. University Publ.,
Leningrad, 1963 (in Russian).
8. Physico-chemical Properties of Semiconductor
Materials. Reference book. Ed. by
A.V. Novoselova and V.B. Lazarev. Nauka,
Moscow, 1979 (in Russian).
9. P.I. Baranskii, V.P. Klochkov, I.V. Potykevich,
Semiconductor Electronics. (The material
properties.) Reference book. Naukova Dumka,
Kiev, 1975 (in Russian).
10. Z.Yu. Gotra, The Technology of Microelectronic
Devices. Radio i Svyaz’, Moscow, 1991 (in
Russian).
11. Solid State Physics. Encyclopaedia. (in
2 Volumes). Ed. by V.G. Baryakhtar and
V.L. Vinetskii. Naukova Dumka, Kiev, Vol. I,
1996; Vol. II, 1998 (in Russian).
12. S.V. Lienkov, О.І. Lykov, V.А. Mokritskii,
V.V. Zubariev, Optoelectronics of Infrared Range:
Materials, Devices, Systems. TsUPL “Poligraf”.
Odessa, 2005 (in Ukrainian).
13. M.S. Sodha, P.C. Eastman, Effect of neutral
impurities on mobility in nondegenerate semi-
conductors // Phys. Rev. 108 (6), p. 1373-1375 (1957).
14. P.I. Baransky, P.М. Kurilo, The Hall effect
investigations of symmetry properties of
isoenergetic surfaces in p-Ge // Fizika tverdogo
tela, 6 (1), p. 54-57 (1964), in Russian.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 1. P. 25-28.
PACS 61.82.Fk, 61.72.uf, 61.72.S-, 72.20.-i
Investigation of the influence of isovalent impurity of silicon
and (-irradiation (60Co) on electrophysical parameters of n-Ge (Sb(
G.P. Gaidar
Institute for Nuclear Research, National Academy of Sciences of Ukraine,
47, prospect Nauky, 03680 Kyiv, Ukraine; e-mail: gaydar@kinr.kiev.ua
Abstract. The influence of isovalent impurity of Si on the kinetics of electron processes in n-Ge (Sb( single crystals has been investigated. It has been shown that in the region of predominant impurity scattering (at Т ( 77.4 K), the presence of isovalent impurity significantly reduces the mobility of charge carriers and changes the sign of inequality
1
/
K
4
.
77
K
300
>
e
e
n
n
characteristic of n-Ge (Sb( single crystals to the opposite one. It has found that in n-Ge (Sb( samples irradiated by (-rays (60Co) with the dose 1.23(108 R, the charge carrier mobility has low radiation stability and decreases with increasing the magnetic field, while remaining practically unchanged in the region of the intermediate Н values.
Keywords: germanium, isovalent impurity, silicon, γ-irradiation, Hall effect, charge carrier mobility, electron concentration.
Manuscript received 11.11.13; revised version received 26.12.13; accepted for publication 20.03.14; published online 31.03.14.
1. Introduction
For most of problems of the applied character, it is important not only a high degree of homogeneity of the crystal, but what kind and state of impurity are available in its bulk, since all this, ultimately, influences the concentration of charge carriers and their mobility. These problems can be solved by investigating crystals in various aspects:
a)
by direct studying the influence of certain chemical elements on their electrical properties;
b)
by revealing features of the influence of semiconductor compensating impurities on these properties;
c)
by analyzing various schemes of complexing and its consequences to which it leads in the crystal bulk.
Concerning electrically active impurities, at least, basic properties of almost every element leading to formation of singly and multiply charged centers in Ge and Si were studied. More difficult is the situation with the so-called electrically passive impurities of different elements in these crystals. When considering that according to the data of mass-spectroscopic analysis, the content of oxygen in Ge is about 2(1018 cm–3, and the contents of hydrogen and carbon in it are about the same [1], then, naturally, a question arises, what features of charge carrier scattering, for example, may be associated with these impurities, since in other experiments (e.g. when studying absorption of infrared radiation [2]), the presence of these impurities in the crystal bulk is easily singled out. The question concerning the interaction of these impurities with other impurities that are in the n-Ge crystal bulk and resulting formation of various complexes is of particular interest. For example, the impurity atoms of Si in Ge, which are isovalent impurities, may affect transport phenomena occurring in germanium not only as electrically neutral elementary scatterers, but also in the form of neutral or charged complexes. These complexes may arise during interaction of silicon atoms with the atoms of electrically neutral or active impurities that are in the crystal bulk. This fact combined with very little data in the literature relative to the problem of complex formation in Ge (the situation with Si containing isovalent impurity of Ge is somewhat better [3-6]) important in general for physics and chemistry of solids have prompted to undertake studying the influence of Si isovalent impurities on the Hall mobility of charge carriers in n – Ge.
K
4
.
77
K
300
e
e
n
n
r
=
Back in the sufficiently early studies (see, e.g. [7]), it was shown that Si is an electrically neutral impurity relative to Ge, i.e., its atoms found in the bulk of Ge do not lead to appearance of additional charge carriers. However, it can be assumed that the impurity atoms of Si (even in the case of its electrical neutrality) influence on the mobility of charge carriers in the area of impurity scattering. The aim of this study was to experimental determine contribution of this scattering in a resultant value of the mobility. For this goal, comparative experiments using the reference samples of Ge doped with Sb and samples of Ge doped with Sb and Si were carried out.
The scientific literature, as far as it is known [8-12], is very poor in sources related to the study of the kinetics of the electron gas in crystals grown at combined doping (i.e., when doping more than one impurity).
2. Results and discussion
To study the influence of Si isovalent impurity on electrophysical properties of n-Ge doped with an electrically-active impurity of antimony (Sb), ingots, some of which were doped only with Sb impurity (unitary doping) and others besides the Sb impurity were doped with silicon with approximately the same concentration (double or combined doping), were used. From these ingots, two groups of samples (three samples in each group) were prepared. The obtained samples possess suitable sizes and shapes for measurements of the resistivity and Hall effect both at room temperature and at liquid nitrogen one (Fig. 1). The samples in both cases were cut from ingots in the direction of their growth, which coincided with the crystallographic orientation [110]. The magnetic field oriented in the crystallographic direction
H
r
|| [001] was applied perpendicular to the lateral surface of the samples. All the measurements were performed at H = 2340 Oe.
Before soldering current contacts and contacts to the measuring probes, the samples were polished and etched for about 2 min in a boiling solution of 30 % hydrogen peroxide, and then they were washed with distilled water. After the contacts were soldered using pure tin (Sn), the samples were etched again. Before the measurements, the ohmic regime of current contacts was tested at the current values that by several times exceeded the values used in our experiments.
The results of the measurements carried out using the samples of germanium both at 300 K and at 77.4 K are presented in Table.
The results obtained by the experiments (Table) show that the insertion of isovalent impurity of Si in Ge crystals (even more heavily doped with antimony than the 1'–3' samples) leads to a significant change in electrophysical properties of these crystals, which finds its expression in a number of features. For example, the sign of inequality
1
/
K
4
.
77
K
300
>
e
e
n
n
, which is typical for the initial samples (i.e., for n-Ge (Sb(), changes to the opposite one when introducing isovalent silicon atoms into the germanium crystal in addition to doped Sb atoms.
Fig. 1. External view, shape and dimensions (in millimeters) of investigated n-Ge samples.
Table shows that at dominant scattering by the lattice vibrations (i.e., at 300 K), in the samples of unitary and double doping, the values of mobility (300 K are conventional for n-Ge with the concentration of charge carriers 1013…1014 cm–3 and are about 2700...3000 сm2/V(s. However, in the region of predominant impurity scattering (i.e., at 77.4 K), in the crystals of double doping (n-Ge (Sb+Si(), values of the charge carrier mobility (77.4 K are considerably lower than those in the samples of unitary doping. Thus, the isovalent impurity of Si atoms, being electrically passive, significantly reduces the mobility of charge carriers in Ge crystals, doped with electrically active impurity of Sb as a consequence of manifestation of the additional scattering of charge carriers by neutral centers [13]. This result may be caused by some difference in the tetrahedral radii of Si and Ge (rSi = 1.17 Å; rGe = 1.22 Å) and, therefore, the emergence of local internal stresses of the lattice around Si atoms. It can also be a manifestation of imperfections of the Ge lattice doped with Si, which is caused, in turn, by non-uniformity in distribution of Si impurity in the bulk of the studied crystals.
The values of the mobility of charge carriers in the samples of double doping were not only smaller than the values (77.4 K, typical for samples of unitary doping, but they were also less sensitive (by approximately 1.3 times) to the concentration of dopant in the bulk of the samples. This is clear from the fact that, at the temperature 77.4 K, an increase of the concentration of dopant ne in n-Ge (Sb( crystals by 33 % results in a decrease of the charge carrier mobility in these crystals by 8 %, while in the crystals of double doping (n-Ge (Sb+Si(), an increase of the concentration of electrically active impurity almost twice (or, more precisely, by 85 %) provides a reduce of the mobility only by 13 %.
0
2
4
6
8
10
12
14
16
18
20
22
24
0.7
0.8
0.9
1.0
1.1
H
, kOe
T
» 77.4 K
T
» 300 K
R
H
/
R
0
1
2
3
4
Fig. 2. Dependences RH/R0 = f(H) obtained in the experiments with n-Ge crystals doped with Si at Т ( 300 K (curves 1 and 2) and at Т ( 77.4 K (curves 3 and 4). Curves 1 and 3 for the sample 2 (( 300 K = 11.8 Ohm(cm), curves 2 and 4 for the sample 3 (( 300 K = 7.6 Ohm(cm) (see Table).
10
3
10
4
10
5
10000
15000
20000
25000
H
, Oe
m
, сm
2
/V
×
s
1
2
Fig. 3. Dependences ( = ( (Н) of n-Ge (Sb( crystals before (1) and after (2) (-irradiation (60Со) with the dose 1.23(108 R. The current and the magnetic field were directed as follows:
J
r
|| [110],
H
r
|| [001].
The fact that well-known literature lacks data on the dependence of the Hall coefficient on the magnetic field value in Ge doped with Si causes not only a technical difficulty in the processing of Hall data, but also a substantial obstacle in obtaining unambiguous results for the Hall mobility of charge carriers in these crystals. In relation with it, the measurements of the dependence of the Hall coefficient on the magnetic field value in Ge samples doped with Sb and Si were carried out.
The results of these experiments fulfilled both at room temperature and at 77.4 K (Fig. 2), in fact, are typical for n-Ge (free from the Si impurities), which was studied in similar conditions [14].
In samples prepared from the ingot of unitary doping n-Ge (Sb( (with antimony impurity doped in melt NSb = ne = 1.2(1014 cm–3), in which the concentration of atomically dispersed oxygen (determined by IR-absorption spectra) was (1.2(1017 cm–3, the study of the dependence of Hall mobility on the magnetic field value before (initial three samples) and after (-irradiation (60Co) with the dose 1.23(108 R was carried out. The vectors of the current
J
r
and magnetic field
H
r
in the samples were directed as follows:
J
r
|| [110],
H
r
|| [001].
The dependences of the mobility of charge carriers on the magnetic field intensity in n-Ge (Sb( crystals before and after (-irradiation are presented in Fig. 3.
Fig. 3 shows that the mobility under the influence of (-irradiation significantly changed only in weak and strong magnetic fields H, while in the intermediate fields this parameter (with respect to the used dose) was almost unchanged. However, the decrease in the carrier mobility with increasing the magnetic field in the samples before and after (-irradiation had progressive character.
Thus, from the results of our measurements, it can be concluded that in the initial samples Ge (Sb( of n-type with atomically dispersed (electrically neutral) oxygen impurity, the mobility of charge carriers has low radiation resistance (mobility ( decreases under the influence of γ-irradiation).
3. Conclusions
In this paper, the influence of Si isovalent impurity on the Hall effect and electrical conduction in n-Ge single crystals doped with electrically active impurity of Sb has been investigated. It has been shown that mainly in the field of impurity scattering (at Т ( 77.4 K), the presence of electrically passive impurity of silicon in the germanium bulk significantly reduces the mobility of charge carriers, which is, probably, the result of a manifestation of both additional carrier scattering by neutral centers and changes in scattering caused by lattice vibrations owing to violation of its structure as a result of some difference in the covalent radii of matrix atoms (Ge) and isovalent impurity (Si).
It has been found that in the crystals of double doping (n-Ge (Sb+Si(), the sign of inequality
1
/
K
4
.
77
K
300
>
e
e
n
n
characteristic of n-Ge (Sb( single crystal changes to the opposite one.
It has been found that in the unitary doped n-Ge (Sb( samples irradiated by γ-quanta (60Со) with the dose 1.23(108 R, the mobility of charge carriers has low radiation stability, and it decreases with increasing the magnetic field value. The changes are more significant in weak and strong magnetic fields H, while for the intermediate H values this parameter remains practically unchanged.
References
1. B.I. Boltaks, Diffusion and Point Defects in Semiconductors. Nauka, Leningrad, 1972 (in Russian).
2. А.А. Groza, P.G. Litovchenko, М.І. Starchik, The Effects of Radiation in the Infrared Absorption and Structure of Silicon. Naukova Dumka, Kiev, 2006 (in Ukrainian).
3. L.I. Khirunenko, V.I. Shakhovtsov, V.V. Shumov, The radiation defect formation in Ge-doped silicon under low-temperature irradiation // Fizika i tekhnika poluprovodnikov, 32 (2), p. 132-134 (1998) (in Russian).
4.
C.V. Budtz-Jorgensen, P. Kringhoj, A.N. Larsen, N.V. Abrosimov, Deep-level transient spectroscopy of the Ge-vacancy pair in Ge-doped n-type silicon // Phys. Rev. B, 58 (3), р. 1110-1113 (1998).
5. Yu.V. Pomozov, M.G. Sosnin, L.I. Khirunenko, V.I. Yashnik, N.V. Abrosimov, W. Shroder, M. Hohne, Oxygen-related radiation defects in
Si1–xGex // Fizika i tekhnika poluprovodnikov 34 (9), p. 1030-1034 (2000), in Russian.
6. L.I. Khirunenko, V.I. Shakhovtsov, V.K. Shinkarenko, L.I. Shpinar, I.I. Yaskovets, Characteristic properties of radiation-induced defect formation in crystals Si(Ge( // Fizika i tekhnika poluprovodnikov, 21 (3), p. 562-565 (1987), in Russian.
7. N.A. Gopiunova, Chemistry of Diamond-like Semiconductors. Leningrad. University Publ., Leningrad, 1963 (in Russian).
8. Physico-chemical Properties of Semiconductor Materials. Reference book. Ed. by A.V. Novoselova and V.B. Lazarev. Nauka, Moscow, 1979 (in Russian).
9. P.I. Baranskii, V.P. Klochkov, I.V. Potykevich, Semiconductor Electronics. (The material properties.) Reference book. Naukova Dumka, Kiev, 1975 (in Russian).
10. Z.Yu. Gotra, The Technology of Microelectronic Devices. Radio i Svyaz’, Moscow, 1991 (in Russian).
11. Solid State Physics. Encyclopaedia. (in 2 Volumes). Ed. by V.G. Baryakhtar and V.L. Vinetskii. Naukova Dumka, Kiev, Vol. I, 1996; Vol. II, 1998 (in Russian).
12. S.V. Lienkov, О.І. Lykov, V.А. Mokritskii, V.V. Zubariev, Optoelectronics of Infrared Range: Materials, Devices, Systems. TsUPL “Poligraf”. Odessa, 2005 (in Ukrainian).
13. M.S. Sodha, P.C. Eastman, Effect of neutral impurities on mobility in nondegenerate semiconductors // Phys. Rev. 108 (6), p. 1373-1375 (1957).
14. P.I. Baransky, P.М. Kurilo, The Hall effect investigations of symmetry properties of isoenergetic surfaces in p-Ge // Fizika tverdogo tela, 6 (1), p. 54-57 (1964), in Russian.
Table. Electrophysical parameters of n-Ge single crystals for unitary (Ge (Sb() and double doping (Ge (Sb+Si().
Dopant�
Number of
n-Ge sample�
Т ( 300 K�
Т ( 77.4 K�
� EMBED Equation.3 ����
�
�
�
R,
сm3/Coul�
ne,
сm�3�
(,
сm2/V(s�
R,
сm3/Coul�
ne,
сm–3�
(,
сm2/V(s�
�
�
Sb+Si�
1�
5.09(105�
1.23(1014�
2960�
4.70(105�
1.33(1014�
23100�
0.925�
�
�
2�
3.70(104�
1.69(1014�
2680�
3.65(104�
1.76(1014�
19600�
0.960�
�
�
3�
2.86(104�
2.18(1014�
3200�
2.54(104�
2.46(1014�
20500�
0.886�
�
Sb�
1'�
9.04(105�
6.92(1013�
3070�
1.08(105�
5.78(1013�
29200�
1.197�
�
�
2'�
8.09(104�
7.74(1013�
3050�
9.70(104�
6.90(1013�
28300�
1.122�
�
�
3'�
6.90(104�
9.08(1013�
2560�
8.15(104�
7.68(1013�
27000�
1.182�
�
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
25
_1452415253.unknown
_1452416364.unknown
_1452416365.unknown
_1452415262.unknown
_1452415276.unknown
_1452415258.unknown
_1452415107.unknown
_1452415174.unknown
_1451131778.unknown
_1452414847.unknown
_1451129645.unknown
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