Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide
The photosensitive In₂O₃-p-InSe heterostructures, in which the In₂O₃ frontal layer has a nanostructured surface, have been investigated. The photoresponse spectra of these heterostructures have been found as essentially dependent on surface topology of oxide. The obtained results indicate that In...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2012
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| Cite this: | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide / V.M. Katerynchuk, Z.R. Kudrynskyi // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2012. — Т. 15, № 3. — С. 214-217. — Бібліогр.: 11 назв. — англ. |
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| citation_txt | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide / V.M. Katerynchuk, Z.R. Kudrynskyi // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2012. — Т. 15, № 3. — С. 214-217. — Бібліогр.: 11 назв. — англ. |
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| description | The photosensitive In₂O₃-p-InSe heterostructures, in which the In₂O₃ frontal
layer has a nanostructured surface, have been investigated. The photoresponse spectra of
these heterostructures have been found as essentially dependent on surface topology of
oxide. The obtained results indicate that In₂O₃ oxide is not only an active component of
the structure but also acts as a diffraction cell element. Oxide surface topology was
investigated using the atomic-force microscope technique. Under different conditions of
InSe oxidation, the sample surfaces contained nanoformations preferably in the form of
nano-islands. Their location acquired both disordered and ordered characters. A
dimensional optical effect in the oxide layer was found to be due to the anisotropic light
absorption in InSe. The higher deviation of incident light from its normal direction due to
a nanostructured surface is, the higher variation in generation of carriers in this
semiconductor is. These changes consist in the energy broadening of the heterostructure
photoresponse spectrum as well as in peculiarities of the excitonic line. The higher
density and ordering of the nanoneedles on the oxide surface is, the higher long-wave
shift and more intense excitonic peak in spectrum takes place.
|
| first_indexed | 2025-12-07T16:08:51Z |
| format | Article |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 2. P. 214-217.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
214
PACS 61.14.Lj, 81.16.Dn, 81.65.Mq
Photoelectric properties of In2O3-InSe heterostructure
with nanostructured oxide
V.M. Katerynchuk, Z.R. Kudrynskyi
Chernivtsi Department of the I.M. Frantsevych Institute of Materials Science Problems, NAS of Ukraine,
5, Iryna Vilde str., 58001 Chernivtsi, Ukraine
E-mail: chimsp@ukrpost.ua
*Corresponding author: phone: 0372-525155; fax.: 03722-36018. e-mail: valkater@mail.ru
Abstract. The photosensitive In2O3-p-InSe heterostructures, in which the In2O3 frontal
layer has a nanostructured surface, have been investigated. The photoresponse spectra of
these heterostructures have been found as essentially dependent on surface topology of
oxide. The obtained results indicate that In2O3 oxide is not only an active component of
the structure but also acts as a diffraction cell element. Oxide surface topology was
investigated using the atomic-force microscope technique. Under different conditions of
InSe oxidation, the sample surfaces contained nanoformations preferably in the form of
nano-islands. Their location acquired both disordered and ordered characters. A
dimensional optical effect in the oxide layer was found to be due to the anisotropic light
absorption in InSe. The higher deviation of incident light from its normal direction due to
a nanostructured surface is, the higher variation in generation of carriers in this
semiconductor is. These changes consist in the energy broadening of the heterostructure
photoresponse spectrum as well as in peculiarities of the excitonic line. The higher
density and ordering of the nanoneedles on the oxide surface is, the higher long-wave
shift and more intense excitonic peak in spectrum takes place.
Keywords: InSe, In2O3, heterostructure, photoelectric properties, atomic-force
microscopy, nanostructured surface.
Manuscript received 09.11.11; revised version received 15.05.12; accepted for
publication 14.06.12; published online 25.09.12.
1. Introduction
The phenomena of diffraction and interference of light
are commonly observed using a diffraction grating or
network. These devices have a periodic structure of
grooves or cells with the sizes comparable to the
wavelength of light. It is of some interest to study
interaction of light with materials that have a
nanostructured surface. The surface nanoobjects can
have a different topology (shape, size) and their
ordering. Since the nanoobject sizes are by an order of
magnitude smaller than, for example, the grating
constant is, the nanostructured surfaces have to possess
the strong diffraction properties.
A surface nanostructured relief can be obtained, in
particular, by formation of the heterostructures [1, 2].
The growth of a heterostructure frontal layer is usually
accompanied with formation of nanostructured objects
on its surface. Varying the growing conditions for this
layer, one can influence the structure of the surface
relief. The frontal layer of the photosensitive
heterostructure also serves as its wide-band-gap window.
At normal incidence of light on the transparent
nanostructured surface and when the dimensional optical
effect (diffraction) to be occurred, it will take place a
deviation of light from its initial direction. Using the
anisotropic crystals as semiconductor substrates, one can
expect that the photoelectric properties of
heterostructures will be determined by degree of light
diffraction.
InSe, GaSe layered crystals serve as examples of
semiconductor substrates with the strongly anisotropic
properties. They are used in many heterostructures due
to the possibility of making the high-quality substrates
by cleaving the crystal [3]. The Іn2O3–ІnSe structure is
one of these heterostructures in which the oxide film is
obtained by thermal oxidation of ІnSe [4]. The
photoresponse spectra of the Іn2O3–ІnSe heterostructures
are essentially different for the Ec and E||c orientations
of the incident light polarization, where E is the electric-
field vector of the electromagnetic wave; c is a
crystallographic axis which is also perpendicular to the
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 2. P. 214-217.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
215
cleavage plane [5]. The use of such heterostructures
serves as an ideal model for detecting the dimensional
optical effects provided that the oxide surface is
nanostructured and the substrate is anisotropic.
The nanoanalysis of InSe surface topology by using
the atomic force microscope (AFM) images confirmed
the formation of nanoobjects on the surface of the as-
cleaved crystals [6], on the surface of the samples
subjected to the influence of the AFM probe [6, 7], and
on the surface of intrinsic oxides of these crystals [8].
The aim of the present article is an experimental
investigation of diffraction properties inherent to the
nanostructured surface in Іn2O3–ІnSe heterostructures.
2. Experimental
InSeCd crystals were used for our investigations. They
were grown from a nonstoichiometric melt of the InSe
composition by using the Bridgman technique and had
p-type conductivity [9]. The crystalline substrates were
cut out from the ingot and were like the plane-parallel
plates with dimensions close to 10×5×0.3…0.4 mm.
These substrates were placed in an electric furnace,
where they were kept for various times in air at the
temperature 420 °С. The oxidation temperature was
arbitrarily chosen. After thermal oxidation, the samples
were investigated to ascertain oxide surface topology.
The atomic force microscope Nanoscope IIIа Dіmensіon
3000 SPM (Dіgіtal Іnstruments, USA) was used for this
purpose.
Conducting properties of ІnSe intrinsic oxide were
also used to prepare two types of the Іn2O3–ІnSe
photosensitive heterostructures with a np -junction
location relative to c: N||c and Nc (N is the vector
normal to the np -junction plane) [1]. The procedure
of heterostructures preparation was as follows. Only one
facet with oxide film was kept in oxidized samples.
Oxides on other their facets were removed by cutting off
and cleaving the corresponding end surfaces. Pure
indium was used as material for ohmic contacts. The
photoresponse spectra of heterostructures were
investigated using the MDR-3 monochromator (Russia).
A spectral resolution was not worse than 13 Å/mm. All
the spectra were normalized to unity quantum efficiency.
3. Results and discussion
AFM-images of the ІnSe unoxidized and oxidized
surfaces are shown in Fig. 1. They demonstrate that the
oxide surface topology and nanoobject sizes can be
varied by processing conditions when oxidizing the
substrate surfaces. We considered some peculiarities of
surface topology in detail. The mean arithmetic
roughness value Ra was determined to be 0.053 nm for
the unoxidized surface in the plane (0001) (Fig. 1a). This
value confirms a conclusion about the high quality of the
crystal cleavage. After oxidation of the samples for
15 min, formed on the ІnSe surface are clusters of oxide
crystallites that were painted with white color in Fig. 1b.
They were risen above the surface, distributed randomly
and have an indefinite form. The crystallite lateral sizes
reached approximately one hundred nanometers. The
height of single crystallites determined by the sectіon
analysis method did not exceed 1 nm. The sizes of the
unoxidized areas (dark-colored) were decreased for the
samples oxidized for 1 h (Fig. 1c). The value of Ra was
increased up to ~0.631 nm. The single crystallites had a
look of high nano-islands. Their height attained 10 nm.
Appearance of these groups of nano-islands can be
related with different times of their formation on the
ІnSe surface and peculiarities of the crystallites
coalescence. The oxide crystallites transform in a more
uniform ensemble of nano-islands with increasing the
oxidation time up to 5 h (Fig. 1d). On the basis of
statistical analysis by using the АFМ-image, the surface
density of nano-islands was estimated as 29 cm104 .
The average values of the nano-islands sizes are: h =
5.22.44 nm and d = 50.67.2 nm, where h is their
height, and d is the diameter of their base. It should be
noted that in Fig. 1d the scale of the vertical axis is 10
times less than the scale in the horizontal plane.
Therefore, the real shape of these nano-islands is a low
cone. After oxidation of the samples for 20 h, the oxide
crystallites are transformed from a needle-shaped to
dome-like shape (Fig. 1e). Their height and base attain
50 and 200 nm, respectively. Thus, the ordered nano-
islands ensemble can be formed on the In2О3 surface by
optimization of processing conditions.
The photoresponse spectra of the Іn2O3–ІnSe
heterostructures with the nanostructured oxide are shown
in Fig. 2a. They were investigated in the range of the
fundamental absorption edge of light for all the
oxidation regimes. The spectra for the samples with two
localizations of np -junction relatively to the с-axis
are illustrated in Fig. 2b. Dynamics of the spectra
behavior in Fig. 2a consists in their long-wave shift and
the appearance on them the fine structure in the form of
peak as a result of changing the oxidation conditions.
The greater the sizes of nano-islands and higher their
ordering on the oxide surface, the more pronounced is
the energy shift of the photoresponse edge and more
intense is the peak in the spectrum (curve 4, Fig. 2a). A
change of the surface relief in direction of decreasing
its roughness results in decreasing the above
peculiarities in the spectra (curve 5, Fig. 2a). The
maximum value of the edge shift equals approximately
0.13 eV. To explain the results obtained involving the
different topology of oxide surface, one should take into
account the behavior of the photoresponse spectra of the
Іn2O3–ІnSe heterostructures obtained for two
orientations of light polarization plane: Ec and E||c
(Fig. 2b). One can see from Fig. 2b that the
corresponding spectra are also shifted, and one of them
(in the case E||c) has a peak, too. Low-temperature
investigations of the spectra have indicated that the edge
peaks take place for both cases of illumination [5, 10].
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 2. P. 214-217.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
216
Fig. 1. AFM images of unoxidized (a) and oxidized (b-e) InSe (0001) surfaces; oxidation at 420 °C for 0.25 (b), 1 (c), 5 (d),
and 20 h (e).
These peaks involve the formation of excitons. Since the
exciton binding energy in InSe is also anisotropic, the
peak is only observed at room temperature in the case
E||c, when Ry > kT (Ry is the exciton Rydberg, k –
Boltzmann constant, T – absolute temperature) [1]. The
long-wave shift of the spectrum for polarization E||c is
caused by changing a type of the interband transitions:
allowed in the case E||c and forbidden for Ec [11].
A comparison of these results testifies that the
nanostructured surface of oxide causes diffraction of
beams, i.e. it changes the angle between E and c vectors.
The nano-islands ordered ensemble should be assumed
to act as a diffraction network with the nanosized cells.
In the case of the spectrum shown in Fig. 2а (curve 4),
the deviation of beams from their normal incidence is so
great that it corresponds practically to the case of
illumination of samples for polarization E||c (curve 1,
Fig. 2b). Thus, the nanostructured surface ordered
promotes to the strong diffraction of light.
The revealed properties can be used to optimize
photoelectrical parameters of Іn2O3–ІnSe
heterostructures with the nanostructured oxide layer.
Since the absorption coefficient of light in InSe is
anisotropic, and it is higher in polarization E||c as
compared with Ec, the generation region of
photocarriers and the coefficient of their collection by a
barrier can be essentially changed under illumination of
these heterostructures.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 2. P. 214-217.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
217
1.10 1.15 1.20 1.25 1.30 1.35
0
0.2
0.4
0.6
0.8
1.0
1
2
3
4
5
P
ho
to
re
sp
on
se
, a
rb
. u
. a
1.0 1.5 2.0 2.5
0
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Fig. 2. Room temperature photoresponse spectra for In2O3-p-
InSe heterostructures at different geometry of illumination: a)
Ec, 0 (1), 0.25 (2), 1 (3), 5 (4), and 20 h (5) oxidation time;
b) E||c (1) and Ec (2).
It should be noted that in investigated
heterostructures the surface properties change of oxide
and its thickness can also influence on the
photoelectrical parameters of these structures. In this
relation, there is of interest a future study of the
influence of a surface roughness on the light reflection
coefficient of oxide. The antireflection effect of oxide
films on photoelectrical characteristics of structures was
also not taken into account. It is related to that
interference effects in the photocurrent spectra were not
observed.
4. Conclusions
Іn2O3 conducting oxide films were obtained by thermal
oxidation of InSe crystals at 420 °С. The surface
structure of the unoxidized and oxidized crystals was
examined using an atomic force microscope. Topology
of the surface nanoobjects was established to be changed
in dependence on oxidation time. The highest order of
nanoobjects like the observed ensemble of nano-islands
was obtained for the samples oxidized for 5 h.
Photosensitivity and photoresponse spectra of
Іn2O3–ІnSe heterostructures with the oxide
nanostructured surface depend on the degree of ordering
the surface nanoobjects. This is indicative of diffraction
properties the nanostructured surface. The higher
uniformity and ordering of nanoobjects, the stronger
diffraction of beams occurs and the greater are changes
in the photoresponse spectra. The changes in the spectra
are analogous to those caused by orientation of samples
when illuminating them with polarized light from Ec to
E||c.
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P.S. Kop’ev, Zh.I. Alferov, D. Bimberg, Quantum
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|
| id | nasplib_isofts_kiev_ua-123456789-118313 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1560-8034 |
| language | English |
| last_indexed | 2025-12-07T16:08:51Z |
| publishDate | 2012 |
| publisher | Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| record_format | dspace |
| spelling | Katerynchuk, V.M. Kudrynskyi, Z.R. 2017-05-29T16:48:42Z 2017-05-29T16:48:42Z 2012 Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide / V.M. Katerynchuk, Z.R. Kudrynskyi // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2012. — Т. 15, № 3. — С. 214-217. — Бібліогр.: 11 назв. — англ. 1560-8034 PACS 61.14.Lj, 81.16.Dn, 81.65.Mq https://nasplib.isofts.kiev.ua/handle/123456789/118313 The photosensitive In₂O₃-p-InSe heterostructures, in which the In₂O₃ frontal layer has a nanostructured surface, have been investigated. The photoresponse spectra of these heterostructures have been found as essentially dependent on surface topology of oxide. The obtained results indicate that In₂O₃ oxide is not only an active component of the structure but also acts as a diffraction cell element. Oxide surface topology was investigated using the atomic-force microscope technique. Under different conditions of InSe oxidation, the sample surfaces contained nanoformations preferably in the form of nano-islands. Their location acquired both disordered and ordered characters. A dimensional optical effect in the oxide layer was found to be due to the anisotropic light absorption in InSe. The higher deviation of incident light from its normal direction due to a nanostructured surface is, the higher variation in generation of carriers in this semiconductor is. These changes consist in the energy broadening of the heterostructure photoresponse spectrum as well as in peculiarities of the excitonic line. The higher density and ordering of the nanoneedles on the oxide surface is, the higher long-wave shift and more intense excitonic peak in spectrum takes place. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide Article published earlier |
| spellingShingle | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide Katerynchuk, V.M. Kudrynskyi, Z.R. |
| title | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide |
| title_full | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide |
| title_fullStr | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide |
| title_full_unstemmed | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide |
| title_short | Photoelectric properties of In₂O₃-InSe heterostructure with nanostructured oxide |
| title_sort | photoelectric properties of in₂o₃-inse heterostructure with nanostructured oxide |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/118313 |
| work_keys_str_mv | AT katerynchukvm photoelectricpropertiesofin2o3inseheterostructurewithnanostructuredoxide AT kudrynskyizr photoelectricpropertiesofin2o3inseheterostructurewithnanostructuredoxide |