The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base
In this paper the mechanism of current’s transport in the structure Al-p-CdTe-Mo is studied, when the thickness of the base w ≤ 10 μm. The results of study of current-voltage characteristics of the structure Al-p-Cd-Te-Mo with different thicknesses of the base and the influence of the thickness of t...
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Науковий фізико-технологічний центр МОН та НАН України
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| Цитувати: | The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base / Sh.A. Mirsagatov, A.K. Uteniyazov // Физическая инженерия поверхности. — 2015. — Т. 13, № 3. — С. 325-329. — Бібліогр.: 15 назв. — англ. |
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irk-123456789-1087602016-11-16T03:02:46Z The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base Mirsagatov, Sh.A. Uteniyazov, A.K. In this paper the mechanism of current’s transport in the structure Al-p-CdTe-Mo is studied, when the thickness of the base w ≤ 10 μm. The results of study of current-voltage characteristics of the structure Al-p-Cd-Te-Mo with different thicknesses of the base and the influence of the thickness of the base on the mechanism of current’s transport are given. В работе исследуется механизм переноса тока в структуре Al-p-CdTe-Mo, когда толщина базы w ≤ 10 μm. Приведены результаты исследований вольт-амперных характеристик структуры Al-p-CdTe-Mo с разными толщинами базы и влияния толщины базы на механизм переноса тока. У роботі досліджується механізм перенесення струму в структурі Al-p-CdTe-Mo, коли товщина бази w ≤ 10 μm. Наведено результати досліджень вольт-амперних характеристик структури Al-p-CdTe-Mo з різними товщинами бази та впливу товщини бази на механізм перенесення струму. 2015 Article The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base / Sh.A. Mirsagatov, A.K. Uteniyazov // Физическая инженерия поверхности. — 2015. — Т. 13, № 3. — С. 325-329. — Бібліогр.: 15 назв. — англ. 1999-8074 http://dspace.nbuv.gov.ua/handle/123456789/108760 53.043, 53.023.539.234 en Физическая инженерия поверхности Науковий фізико-технологічний центр МОН та НАН України |
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In this paper the mechanism of current’s transport in the structure Al-p-CdTe-Mo is studied, when the thickness of the base w ≤ 10 μm. The results of study of current-voltage characteristics of the structure Al-p-Cd-Te-Mo with different thicknesses of the base and the influence of the thickness of the base on the mechanism of current’s transport are given. |
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Article |
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Mirsagatov, Sh.A. Uteniyazov, A.K. |
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Mirsagatov, Sh.A. Uteniyazov, A.K. The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base Физическая инженерия поверхности |
| author_facet |
Mirsagatov, Sh.A. Uteniyazov, A.K. |
| author_sort |
Mirsagatov, Sh.A. |
| title |
The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base |
| title_short |
The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base |
| title_full |
The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base |
| title_fullStr |
The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base |
| title_full_unstemmed |
The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base |
| title_sort |
mechanism of current transport in the structure al-p-cdte-mo with different thickness of the base |
| publisher |
Науковий фізико-технологічний центр МОН та НАН України |
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2015 |
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http://dspace.nbuv.gov.ua/handle/123456789/108760 |
| citation_txt |
The mechanism of current transport in the structure Al-p-CdTe-Mo with different thickness of the base / Sh.A. Mirsagatov, A.K. Uteniyazov // Физическая инженерия поверхности. — 2015. — Т. 13, № 3. — С. 325-329. — Бібліогр.: 15 назв. — англ. |
| series |
Физическая инженерия поверхности |
| work_keys_str_mv |
AT mirsagatovsha themechanismofcurrenttransportinthestructurealpcdtemowithdifferentthicknessofthebase AT uteniyazovak themechanismofcurrenttransportinthestructurealpcdtemowithdifferentthicknessofthebase AT mirsagatovsha mechanismofcurrenttransportinthestructurealpcdtemowithdifferentthicknessofthebase AT uteniyazovak mechanismofcurrenttransportinthestructurealpcdtemowithdifferentthicknessofthebase |
| first_indexed |
2025-07-07T22:01:38Z |
| last_indexed |
2025-07-07T22:01:38Z |
| _version_ |
1837027242006282240 |
| fulltext |
Mirsagatov Sh. A., Uteniyazov A. K., 2015 © 325
УДК: 53.043, 53.023.539.234
THE MECHANISM OF CURRENT TRANSPORT IN THE STRUCTURE
Al-p-CdTe-Mo WITH DIFFERENT THICKNESS OF THE BASE
Sh. A. Mirsagatov1, A. K. Uteniyazov2
1Physical technical institute of the Academy of Sciences of Uzbekistan,
Tashkent,
2Karakalpak State University, Nukus,
Received 08.07.2015
In this paper the mechanism of current’s transport in the structure Al-p-CdTe-Mo is studied, when
the thickness of the base w ≤ 10 μm. The results of study of current-voltage characteristics of the
structure Al-p-Cd-Te-Mo with different thicknesses of the base and the influence of the thickness
of the base on the mechanism of current’s transport are given. The above results at current densities
~8.62∙10–8–4.36∙10–5 A/cm2 and ~5.08∙10–7–2,44∙10–5 A/cm2 for samples No. 1 and No. 2, respectively,
were obtained by the theory that takes into account only duffusion components of the current and the
applied voltage to the base of the diode structures. At high current densities ~4.36∙10–5–1.95 A/cm2
and ~2.44∙10–5–3.98 A/cm2 for samples No. 1 and No. 2, respectively, results were obtained by the
theory of the drift current transport mechanism, taking into account the possibility exchange of free
carriers inside the recombination complex.
Keywords: film, Schottky barrier, diode structure.
МЕХАНИЗМ ПЕРЕНОСА ТОКА В СТРУКТУРЕ Al-p-CdTe-Mo
С РАЗЛИЧНОЙ ТОЛЩИНОЙ БАЗЫ
Ш. А. Мирсагатов, А. К. Утениязов
В работе исследуется механизм переноса тока в структуре Al-p-CdTe-Mo, когда толщина базы
w ≤ 10 μm. Приведены результаты исследований вольт-амперных характеристик структуры
Al-p-CdTe-Mo с разными толщинами базы и влияния толщины базы на механизм переноса
тока. Соответственно для образцов № 1 и № 2 при плотностях тока ~8,62∙10–8–4,36∙10–5A/cm2
и ~5,08∙10–7–2,44∙10–5A/cm2 результаты получены по теории, в которой учитываются только
диффузионные составляющие тока и падение приложенных напряжений на толщине базы
в диодных структурах. При больших плотностях тока ~4,36∙10–5–1,95 A/cm2 и ~2,44∙10–5–
3,98 A/cm2, соответственно для образцов № 1 и № 2, результаты получены по теории дрейфо-
вого механизма переноса тока, учитывающей возможность обмена свободными носителями
внутри рекомбинационного комплекса.
Ключевые слова: пленка, барьер Шоттки, диодная структура.
МЕХАНІЗМ ПЕРЕНЕСЕННЯ СТРУМУ В СТРУКТУРІ Al-p-CdTe-Mo
З РІЗНОЮ ТОВЩИНОЮ БАЗИ
Ш. А. Мірсагатов, А. К. Утеніязов
У роботі досліджується механізм перенесення струму в структурі Al-p-CdTe-Mo, коли товщи-
на бази w ≤ 10 μm. Наведено результати досліджень вольт-амперних характеристик структури
Al-p-CdTe-Mo з різними товщинами бази та впливу товщини бази на механізм перенесен-
ня струму. Відповідно для зразків № 1 і № 2 при щільності струму ~8,62∙10–8–4,36∙10–5A/cm2
і ~5,08∙10–7–2,44∙10–5A/cm2 результати отримані по теорії, в якій враховуються тільки дифузійні
складові струму і падіння прикладених напруг на товщині бази в діодних структурах. При
великій щільності струму ~4,36∙10–5–1,95 A/cm2 і ~2,44∙10–5–3,98 A/cm2, відповідно для зразків
№ 1 і № 2, результати отримані з теорії дрейфового механізму перенесення струму, що враховує
можливість обміну вільними носіями всередині рекомбінаційного комплексу.
Ключові слова: плівка, бар’єр Шотткі, діодна структура.
THE MECHANISM OF CURRENT TRANSPORT IN THE STRUCTURE Al-p-CdTe-Mo WITH DIFFERENT THICKNESS OF THE BASE
ФІП ФИП PSE, 2015, т. 13, № 3, vol. 13, No. 3326
INTRODUCTION
Cadmium telluride is widely used to create X-ray
detectors and those of γ-radiation. The mono-
crystal CdTe and Cd1–xZnxTe-detectors have
already demonstrated their advantage over Si
and GaAs-detectors and have been successfully
used for spectrometry and γ-radiation. In the
last years, detectors with Schottky barrier
[1–3], based on CdTe and Cd1–xZnxTe began in-
tensively developed. The essential advantage
of such detectors are small reverse currents
(~10–7 A) and high operating temperature
(T ≥ 300 °K). In addition, detectors based
on the diodes with Schottky barrier can de-
tect high-energy photons with energies
up to 1 MeV and higher within energy limit
[4].
For the first time we obtained in [5] injec-
tion photodetector based on p-type conductivity
coarse-film cadmium telluride with the thick-
ness of the base d ≥ 50 μm, and in [6] current
transport mechanism of injection of photodetec-
tors was examined. Resistance of the base of
these photodetectors was close to the intrinsic
conductivity.
The aim of this study is to investigate the in-
fluence of the thickness of the base on the cur-
rent transport mechanism.
The studied film structures were prepared
using formerly developed technology described
in [7].
Current-voltage characteristics were studied
at the forward (when the «+» was applied to
Mo) and reverse (where «–» was applied to Mo)
directions at the wide range of current and
voltage changes. Total analysis of the current-
voltage characteristics shows that they possess
rectifying properties and their rectification co-
efficient defined as the ratio of forward current
and reverse one at the fixed voltage (5 V), is
more than four orders of magnitude. Figure 1
shows the dependence of current-voltage char-
acteristics for direct current in semi-log scale
for the two types of samples. Current-voltage
characteristics of these samples fit well into
direct lines of fig. 2. Consequently, they are
described by dependence of type J ~ AVα. Seg-
uence of the current-voltage characteristics’
parts of the sample are different at forward cur-
rent and at reverse one.
100
Ig
J,
A
/c
m
2
10–1
10–2
10–3
10–4
10–5
10–6
10–7
10–8
0 2 4 6 8
U, V
10
1
2
3
4
a
b
100
J,
A
/c
m
2
10–1
10–2
10–3
10–4
10–5
10–6
10–7
10–8
0 2 4 6 8
U, V
10
1
2
3
4
Fig. 1. Direct branch of the CVC for typical Schottky
barrier diodes (Al-p-CdTe-Mo) in semi-log scale in the
dark at T = 300 K. The area of Al-contact S ≈ 0.07 cm2,
(a – w = 8 µm, ρ ≈ 2·108 Ω∙cm, base — sample No. 1,
b – w = 10 µm, ρ ≈ 2·107 Ω∙cm, base — sample No. 2)
100
Ig
J,
A
/c
m
2
10–1
10–2
10–3
10–4
10–5
10–6
10–7
10–8
0,01 0,1 1
U, V
10
4
3
2
1
a
100
J,
A
/c
m
2
10–1
10–2
10–3
10–4
10–5
10–6
10–7
10–8
1Е-3 0,01 0,1 1
U, V
10
4
3
2
1
b
Fig. 2. Direct branch of the CVC for typical Schottky di-
odes (Al-p-CdTe-Mo) in double logarithmic scale in the
dark at T = 300 K. The area of Al-contact S ≈ 0.07 cm2,
(a – w = 8 µm, ρ ≈ 2·108 Ω∙cm, base — sample No. 1,
b – w = 10 µm, ρ ≈ 2·107 Ω∙cm, base — sample No. 2)
SH. A. MIRSAGATOV, A. K. UTENIYAZOV
ФІП ФИП PSE, 2015, т. 13, № 3, vol. 13, No. 3 327
equal to one, C = 1 and the potential barrier’s
height is calculated as it is described in [6],
equal respectively to W = 0,84 eV and W = 0,83
eV for samples No. 1 and No. 2.
The second part of the characteristic
(see. Figure 1) is probably described as in [6] by
the theory of V. I. Stafeev [9], because in it value
of the exponent (c) more than 2 and it is equal
to 4.05 and 4.08 for samples No. 1 and No. 2
respectively. Current-voltage characteristics is
described [9]:
, (1)
where
and
o 2 1 ρ
tg
2
n
n
n
wch
LkT SI
q b L w
L
, (2)
here b = μn/μp — the ratio of electron’s and
hole’s mobilities. At the second part have been
also identified the pre-exponential factors, they
are 1.59∙10–8A and 6.43∙10–8A. Using the above
mentioned experimental data and formulas (1)
and (2) values of the diffusion length of minor-
ity carriers-electron Ln, mobility product for the
lifetime of the electron — μn·τn and the resistiv-
ity of the base — ρ, were determined for the
values w ≈ 8 μm, w ≈ 10 μm for samples No. 1
and number 2, respectively, b = μn/μp = 10 [8]
and T = 300 K. Table 1 gives also the param-
eters calculated from the third and fourth parts
of CVC from formulas (1) and (2) to compare
the results.
0 1
qV
ckTI I e
= −
1
2
+
++
=
b
b
L
wbCh
C n
EXPERIMENTAL RESULTS AND
DISCUSSION
Direct branch of CVC measured in the dark
at room temperature is shown in Fig.1. As the
figure shows the direct branch of the CVC
consists mainly of four parts, which are
described by the following exponential
functions:
1) ( )01 1exp / 1I I qV c kT= − , where 11 =c
and I01 = 2.61·10–9 A;
2 ) ( )02 2exp / 1I I qV c kT= − , w h e r e
c2 = 4.05 и I02 = 1.59·10–8 A;
3 ) ( )03 3exp / 1I I qV c kT= − , w h e r e
c3 = 23.98 and I03 = 1.96·10–5 A;
4 ) ( )04 4exp / 1I I qV c kT= − , w h e r e
c4 = 73.62 and I04 = 1.93·10–3 A for the sample
No. 1 and
1) ( )01 1exp / 1I I qV c kT= − , where 11 =c
and I01 = 3.32·10–9 A;
2 ) ( )02 2exp / 1I I qV c kT= − , w h e r e
c2 = 4.08 and I02 = 6.43·10–8 A;
3 ) ( )03 3exp / 1I I qV c kT= − , w h e r e
c3 = 16.96 and I03 = 6.72·10–5 A;
4 ) ( )04 4exp / 1I I qV c kT= − , w h e r e
c4 = 78.96 and I04 = 3.86·10–3 A for the sample
No. 2.
In the first part of the CVC the current is
probably limited by the thermal electron emis-
sion [8]. Since ideal factor for both samples is
Table 1
Parameters, determined from the first parts of the CVC
Number
of sample C W/L Ln, μm μnτn, сm2∙V–1 τn, s I0, А ρ, Ω∙сm
1
4.05 1.87 4.27 7.01∙10–6 7.01∙10–8 1.59∙10–8 2.48 1010
23.98 3.91 2.04 1.6∙10–6 1.6∙10–8 1.96∙10–5 1.53∙108
73.62 5.07 1.57 9.56∙10–7 9.56∙10–9 1.93∙10–3 4.95∙106
2
4.08 1.88 5.3 1.08∙10–6 1.08∙10–8 6.43∙10–8 4.86∙109
16.96 3.55 2.81 3.04∙10–6 3.04∙10–8 6.72∙10–5 2.55∙107
78.96 5.14 1.94 1.45∙10–6 1.45∙10–8 3.86∙10–3 2.15∙106
THE MECHANISM OF CURRENT TRANSPORT IN THE STRUCTURE Al-p-CdTe-Mo WITH DIFFERENT THICKNESS OF THE BASE
ФІП ФИП PSE, 2015, т. 13, № 3, vol. 13, No. 3328
Results of Table 1 shows that at increas-
ing current density the diffusion length of mi-
nority carriers (electrons) Ln decreases and,
accordingly, mobility product for the lifetime of
electrons — μn·τn , decreases. This experimen-
tal result is explained by rechanging recombina-
tion centers and as a result, decreasing lifetime
of minority nonequilibrium carriers too.
Researhed diode structure at high current den-
sities transforms to the diode structure with
a thick base. If it is so, the current–voltage char-
acteristic of this diode structure at high current
densities should be described well by depen-
dence of the current on voltage of type J ~ Vα
voltage. Indeed, built in double logarithmic
current-voltage characteristics at current den-
sities ~4.36∙10–5–1.95 A/cm2 and ~2.44∙10–5–
3.98 A/cm2, respectively, for samples No. 1 and
No. 2, 3 and 4 parts (See Figure 2) are described
well by the dependence of the current on the
voltage of type J ~ Vα . According to the theory
[10], CVC’s part with a sharp increasing cur-
rent appears when together with point impurities
and defect-impurity centers complex recom-
bination systems involve in recombination
processes. They can be such complexes as «neg-
atively charged acceptor + positively charged
intercenter» or «positively charged donor +
negatively charged vacancy», causing by
recombination-stimulated processes [11,
12], «small donor + vacancy» appearing
from the decay of complex systems [13, 14] and
so on.
So in highly compensated p-CdTe film, to-
gether with simple point defects complex recom-
bination systems are too.
In this case, the rate of recombination is de-
scribed by [10]:
2
1 1 τ
n p i
R
n p i
c c np n
U N
c n n c p p a np
, (3)
where NR — concentration of recombination
centers (complexes); n, p — concentration
of electrons and holes; ni — intrinic con-
centration in the semiconductor; cn, сp —
coefficients of capture of electrons and holes;
n1, p1 — equilibrium concentrations of electrons
and holes on conditions when Fermi level co-
incides with the level of impurities (so-called
statistical Shockley-Read factors); τ i —
time taking into account the inertia of those
or other processes of electronic exchange
within the recombination complex; a-coeffi-
cient depending on the specific type of impu-
rity or defect-impurity complexes (see [10]).
According to the theory [10], CVC’s parts of
type J ~ Vα, where α > 2, are realized when
the recombination of nonequilibrium carri-
ers is delayed, that is, involving complexes
in which the electronic exchange takes place.
In this case, in the denominator of (3)
inequality
1 1 τn p ic n n c p p a np (4)
is realised and CVC has the following analytic
expression:
2
2
1
μ τ μ 1
2 1
_
μ τ
R
A n i n
R n
A n i
b w N w JV N q b C
b w N c DA B J
N a C J J
. (5)
In this case, AN – the concentration of
shallow acceptor centers and the parameter C is
related to the concentration of electrons [10, 15]:
JCn =)0( . (6)
From (5) we can determine such parameters
as / τ , (0), τ
n
R i
i
cN n a (τi — delay time within the
complex, RN the concentration of complexes).
Equating straight line for two given data points
(J1, V1 и J2, V2), we define the value of the
voltage
1 2
1 1
2 1
V VV V JJ J
−
= −
−
, (7)
which then equate to the value
21
μ τ
R
A n i
b w N
A N
SH. A. MIRSAGATOV, A. K. UTENIYAZOV
ФІП ФИП PSE, 2015, т. 13, № 3, vol. 13, No. 3 329
of the formula (5). To determine the param-
eters of the sharp increase of current we
choose three experimental points (V1, J1),
(V2, J2), (V3, J3) and then we compose two
equation for them to determine coefficients B
and D
1 22 1
2 1 2 1
1 1D
J JV VB
J J J J
− − = −
− −
, (8)
( ) ( ) 3 2
3 2 2 1
2 1
3 2
2 3 1 2 2 1
1 1 1 1
J J
V V V V
J J
D
J J
J J J J J J
−
− − −
−
=
−
− − − −
,
(9)
which can be equated to their analytical
value from the formula (5). Using the formula
(5) µnC is determined, and using the formula
(6) we can estimate the concentration of
injected electrons n(0) at the beginning and at
the end of these parts of CVC. All parameters
calculated from the parts of CVC are given in
Table 2.
Experimental results show that at changing
current density concentration of recombination
centers taking part in the processes of current
transport is changed. This implies that at low
current densities CVC is described well by
current-voltage characteristics, which takes into
account the diffusion component of the current.
At the same time for large current densities CVC
is described well by drift current component. Jf
we could have the theory of the current-voltage
characteristics, taking into account both the
diffusion and drift current components, we
would get the full dynamics of the current’s
dependence on voltage.
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Table 2
Parameters determined from the CVC’s parts of type J ~ Vα
Number of
sample Branchesd CVC NR/τi, cm3∙s–1 n(0), cm–3 NA, cm–3 Cn/aτi, cm–3
1
2
J ~ V6
J ~ V2.44
J ~ V5.53
J ~ V2.42
1.72∙1015
4.65∙1015
2.21∙1016
9.6∙1016
7.6∙109–1.12∙1011
8.39∙1012–1.22∙1014
3.17∙109–1.33∙1011
6.74∙1011–8.6∙1012
3.12∙108
6.25∙109
2.21∙109
2.41∙1012
6∙108
4.65∙1011
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