Volume 03 Issue 09-2023
143
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
09
Pages:
143-149
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
A
BSTRACT
The current-voltage characteristics of APN elements manufactured by vacuum anisotron evaporation have
been studied. It was found that there are inhomogeneities in a series of successive p
–
n
–
p transitions.... The
dependence of the current-voltage characteristics of oxygen-enriched environments on temperature and
illumination was tested.
K
EYWORDS
APV element, amnisatron evaporation, potential barriers, photoconductivity, microcrystallites, filling
centres, point, shear resistance, electrical neutrality condition, photo, thermal conductivity concentration,
clusters, capture, photovoltage, photovoltage, photocarriers.
I
NTRODUCTION
The theoretical physicist in the field of solid state
physics, Doctor of Physical and Mathematical
Sciences, and member of the Academy of Sciences
of Uzbekistan Adirovich E.I. et al [1] obtained
semiconductor thin films from gallium arsenide
(GaAS) with anomalously high photovoltage.
(
∼
100 V) using a simple thermal evaporation
method. Later in [2], an anomalously high
photovoltage (~5 V) was also observed in thin
films of series semiconductors belonging to the
АIIIВV group. Karpovich [3] experimentally
established that the magnitude of the anomalous
photovoltaic voltage and its direction vary
depending on the angle of incidence of light on the
Journal
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Research Article
ANOMALOUSLY HIGH DIOTOVOLTAIC EFFECT IN THIN
FILMS OF GALLIUM ARSENIDE
Submission Date:
September 17, 2023,
Accepted Date:
September 22, 2023,
Published Date:
September 27, 2023
Crossref doi:
https://doi.org/10.37547/ijasr-03-09-24
Shohbozjon Ergashev
Lecturer, Fergana Branch Of Tuit Named After Muhammad Al-Khwarizmi, Fergana, Uzbekistan
Volume 03 Issue 09-2023
144
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
09
Pages:
143-149
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
surface of the sample. In their opinion, it is
possible to find a direction in which, when
illuminating a sample with this direction, the
anomalously
high
photovoltage
(APV)
approaches zero, and then the photovoltage
changes polarity. Later it became known that this
state corresponds to the direction of growth of its
microcrystals during the formation of thin GaAS
films [4]. Studies of thin films of gallium arsenide
and other semiconductors have shown that
anomalous diagrams of the dependence of
photovoltage on the angle of illumination are one
of the defining characteristics. These studies
make it possible to determine the physical nature
of the anomalously high photovoltages generated
in APV elements. According to Figelsky [5],
photovoltage (abnormally high) occurs at the
boundary of microcrystals with localized
conditions in the form of surfaces or dislocations
in a semiconductor polycrystalline thin film.
These states are charged and form a potential
barrier. Electron and hole photocarriers, inert
under the influence of light, are generated on one
side of the potential barrier and separated by the
barrier medium [6-11]. They create a potential
difference in neighbouring microcrystals (Fig. 1).
In this case, the following expression is suitable
for the elementary microphotovoltage.
ч
n
ф
н
n
cc
J
кТ
V
q
J
J
=
+
(1)
ƞ
н
-concept of non-primary charge carriers,
∆ƞ
ч
−
concentration of charge carriers formed
under the influence of light.
The photovoltage reaches its maximum value
when the ratio of the currents of the majority
charge carriers and minority charge carriers Jn in
the expression for micro photovoltage is Jos: Jn
<<1. This state means the presence of structural
systems of the p
–
n
–
p or n
–
p
–
n-type at the
boundary of veil-shaped crystallites. One of the
factors causing anomalously high photovoltage is
photodiffusion processes in homogeneous areas
of a thin film (Dember effect) [6,7]. In the
experimental samples,
there are “oxide” areas
between the microcrystals of the curtain, and
their resistance is quite high. These boundary
regions prevent the exchange of intercrystalline-
free carriers. Because the resistivity of the
material evaporated in a vacuum differs from the
resistivity of the thin film obtained from it (much,
several times less).
M
ATERIALS AND METHODS
Quite a lot of work has been published on the
nature of formation, production technology,
features and areas of application of abnormally
high photovoltage (APV) [9]. The mechanism of
the effect in APV technology - the production of
elements from any semiconductor material - is a
sufficient task that requires a solution. These
problems cause differences in the characteristic
parameters of the element. As a result, the
imperfection of practical and theoretical criteria
that clarify the experimental characteristics
causes certain difficulties in the areas of practical
application of APV elements. For these reasons, it
is necessary to deepen and expand the scope of
work in this area. To do this, let's try to clarify the
essence and characteristics of the APV - the
Volume 03 Issue 09-2023
145
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
09
Pages:
143-149
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
element of the current voltage characteristic
(CVC). The point is that if there are potential
obstacles in the heterogeneity of the FSA element,
then in its current-voltage characteristic
nonlinearities of various shapes are observed
(deviation from Oh
m’s law). As a result of
studying the APV element of the current-voltage
characteristic, it will be possible to determine a
criterion that will clarify the mechanism of
formation of APV [10]. To determine the ROS
mechanism, an alternating voltage is applied
under the influence of light, such as the current-
voltage characteristic. Voltage is applied to the
vertical deflection plate (electrode) of the
oscilloscope through a load resistor. It is
proportional to the voltage passing through the
sample. The voltage applied to the sample is
applied to the horizontal electrode plate of the
oscilloscope. As a result, a CVC chart for one
period will appear on the screen. The oscillogram
is studied by taking a photograph (computer
image) from the screen. Nonlinearity in CVC is not
noticeable at low illumination and area but
appears at large values of area and illumination.
Based on the purpose of the study, the absolute
value of voltage and current in the current-
voltage characteristic is important, and not the
absolute (real) value, because the nature of the
current-voltage characteristic curves is shown on
the oscillogram. The sign and magnitude of the
photovoltage associated with illumination
depend on the asymmetry of the current-voltage
characteristic in accordance with the direction of
the external voltage applied to it. As the field
approaches 3.103 V/cm, a sharp increase in
current is observed. In conventional units, the
CVC of samples selected by the anisotron method
of thermal evaporation for unlit (V = 0, Fig. 2-a)
and illuminated (V = 0, Fig. 2-b) conditions are
shown in Fig. 1. From the figure it can be seen that
the approximate slope of CVC obtained for the
case of CVC is x v. If potential barriers "shrink"
under the influence of light, then at high values of
luminous intensity (or illumination), the potential
barriers disappear and the current-voltage
characteristic rectifies (representing the classical
OM connection). This situation occurs at
∆𝑛 =
𝑁
0
𝜒
𝜆
where
𝑁
0
is the concentration of donors and
acceptors, for GaAS about 10
18
cm,
-3
d is the
thickness of the thin film of the AFC element when
it is 1 μm, the concentration of photoelectrons
occurs at ∆n=4∙10
18
cm.
Measuring the current-voltage characteristic
of a thin film
To study the current-voltage characteristics, thin
GaAS films obtained by anisotronic thermal
evaporation in a vacuum were used. Before
starting the measurement process, the sample is
subjected to high-temperature and low-
temperature heat treatment in an oxygen
environment and enriched with oxygen. It is also
possible to use the classical scheme [4] of step-by-
step continuous measurement (current and
voltage)
to
perform
current-voltage
measurements. This method requires lengthy,
complex
(labour-intensive)
measurements.
Therefore, there is a need to optimize the
measuring circuit with high resistance (>109
Ohm). At the same time, the current-voltage
characteristic
can
also
be
studied
oscillographically using technical means of
Volume 03 Issue 09-2023
146
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
09
Pages:
143-149
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
information technology (garnograph). To do this,
you can sample at a low frequency (~50Hz). At
the beginning of the initial (-slant) linear
coordinate in CVC, the connection expands
(increases)
with
increasing
illumination.
However, complete CVC correction is not
observed until 105 lux. Photoconductivity can be
determined by the quality of the difference in
slope tangents in CVC (tgλ1
-
tgλ2=τ). Linearity
does not change with changes in temperature and
illumination (Fig. 3). Fig. Figure 4 shows the
temperature dependence of the electrical
conductivity of samples subjected to heat
treatment at high temperatures
𝟏𝟎
𝟑
𝑻
< 3.2
in an
oxygen environment.
Fig. 1. Temperature dependence of the conductivity of samples obtained in an anisotron
evaporator and subjected to high-temperature heat treatment. (Permeability in additional units)
1
–
transmittance for an unilluminated sample
2
–
transmittance under illumination 5.
Volume 03 Issue 09-2023
147
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
09
Pages:
143-149
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
Fig. 2. Current-voltage dependence for samples subjected to low-temperature heat treatment
𝟏𝟎
𝟑
𝑻
> 4
in an oxygen environment.
(graphically in conventional units)
a)
–
taken at room temperature, 1
–
without lighting 2
–
B = 5,10
3
lux.
∙
b)
–
sample at liquid nitrogen temperature, 1
–
without illumination, 2
–
B = 5,10
3
lux.
∙
Volume 03 Issue 09-2023
148
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
09
Pages:
143-149
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
Fig. 3. CVC for a sample that has undergone heat treatment in an oxygen atmosphere at high
temperature.
C
ONCLUSIONS
The non-standing form of CVC indicates the presence of shunt currents shunting the pn junctions.
According to the condition of electrical neutrality for the current, we can write the expression J = Js*tgλ tan
V.
This expression can be compared with the experiment by introducing
𝐽
𝐽
𝐽
𝑆
𝑡ℎ
𝜏𝑉
𝐽
𝑆
𝜏 =
𝑑𝐽
𝑑𝑉
|
𝑣=0
= 𝜆𝐽
𝑠
corresponds to the permeability of the curtain. If the
𝐽
𝐽
𝑆
𝒻(2𝑉)
connection is used for the BAX of the
illuminated sample, then its graph looks like this (Fig. 4).
Fig. 4. CVC for burning state
At sufficiently high temperatures, CVC in the
illuminated state and CVC in the unilluminated
state, the curtains correspond to a hyperbolic
tangent, which means the presence of p-n-p or n-
p-n junctions in the curtain. The degree of
asymmetry of adjacent junctions causes the
appearance of photoelectric voltage (E.M.F.).
R
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1.
Адирович Э.И., Рубинов В.М., Юабов
Ю.М., ФТТ, 610, 3180, (1964).
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Успенский М.Д., Иванова Н.Г., Маликис
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3.
Карпович И.А.В аб. “Электронно –
дыфчные
и
рекоды
в
Volume 03 Issue 09-2023
149
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
09
Pages:
143-149
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
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