Photoemission spectra of indium selenide
For layered InSe crystals photoluminescence spectra were investigated and the corresponding radiative transitions were analyzed. It was found that along with the band-to-band transitions the radiative ones with participation of impurity levels plays a substantial role in the light emission spectrum...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2006
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| Цитувати: | Photoemission spectra of indium selenide / V.M. Katerynchuk, M.Z. Kovalyuk, M.V. Tovarnitskii // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 4. — С. 36-39. — Бібліогр.: 15 назв. — англ. |
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irk-123456789-1216312017-06-16T03:04:02Z Photoemission spectra of indium selenide Katerynchuk, V.M. Kovalyuk, M.Z. Tovarnitskii, M.V. For layered InSe crystals photoluminescence spectra were investigated and the corresponding radiative transitions were analyzed. It was found that along with the band-to-band transitions the radiative ones with participation of impurity levels plays a substantial role in the light emission spectrum of the semiconductor. This fact is confirmed by the intensities of the radiative bands for the impurity level – c(v)-band transitions and the donor-acceptor recombination. The temperature dependences of the spectrum in the range of 100 to 300 К have also enabled to ascertain the dynamics of these radiative transitions. At the temperatures 180 to 300 К, the bands associated with the indirect transitions involving indirect free excitons are more intensive. At 100…180 К, the intensity of the bands corresponding to the direct transitions with participation of direct free excitons increases. We have determined the energies of the observed photoluminescence bands, and the band diagram of the corresponding radiative transitions in InSe has been built. 2006 Article Photoemission spectra of indium selenide / V.M. Katerynchuk, M.Z. Kovalyuk, M.V. Tovarnitskii // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 4. — С. 36-39. — Бібліогр.: 15 назв. — англ. 1560-8034 PACS 78.55.–m, 78.60.–b http://dspace.nbuv.gov.ua/handle/123456789/121631 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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For layered InSe crystals photoluminescence spectra were investigated and the corresponding radiative transitions were analyzed. It was found that along with the band-to-band transitions the radiative ones with participation of impurity levels plays a substantial role in the light emission spectrum of the semiconductor. This fact is confirmed by the intensities of the radiative bands for the impurity level – c(v)-band transitions and the donor-acceptor recombination. The temperature dependences of the spectrum in the range of 100 to 300 К have also enabled to ascertain the dynamics of these radiative transitions. At the temperatures 180 to 300 К, the bands associated with the indirect transitions involving indirect free excitons are more intensive. At 100…180 К, the intensity of the bands corresponding to the direct transitions with participation of direct free excitons increases. We have determined the energies of the observed photoluminescence bands, and the band diagram of the corresponding radiative transitions in InSe has been built. |
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Article |
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Katerynchuk, V.M. Kovalyuk, M.Z. Tovarnitskii, M.V. |
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Katerynchuk, V.M. Kovalyuk, M.Z. Tovarnitskii, M.V. Photoemission spectra of indium selenide Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Katerynchuk, V.M. Kovalyuk, M.Z. Tovarnitskii, M.V. |
| author_sort |
Katerynchuk, V.M. |
| title |
Photoemission spectra of indium selenide |
| title_short |
Photoemission spectra of indium selenide |
| title_full |
Photoemission spectra of indium selenide |
| title_fullStr |
Photoemission spectra of indium selenide |
| title_full_unstemmed |
Photoemission spectra of indium selenide |
| title_sort |
photoemission spectra of indium selenide |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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2006 |
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http://dspace.nbuv.gov.ua/handle/123456789/121631 |
| citation_txt |
Photoemission spectra of indium selenide / V.M. Katerynchuk, M.Z. Kovalyuk, M.V. Tovarnitskii // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 4. — С. 36-39. — Бібліогр.: 15 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
AT katerynchukvm photoemissionspectraofindiumselenide AT kovalyukmz photoemissionspectraofindiumselenide AT tovarnitskiimv photoemissionspectraofindiumselenide |
| first_indexed |
2025-07-08T20:15:06Z |
| last_indexed |
2025-07-08T20:15:06Z |
| _version_ |
1837111137516126208 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 4. P. 36-39.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
36
PACS 78.55.–m, 78.60.–b
Photoemission spectra of indium selenide
V.M. Katerynchuk, M.Z. Kovalyuk, M.V. Tovarnitskii
I. Frantsevich Institute for Problems of Material Science, NAS of Ukraine, Chernivtsi Department
5, Iryna Vilde str., 58001 Chernivtsi, Ukraine
Phone: (0372) 525155; fax: (03722) 36018; e-mail: chimsp@unicom.cv.ua
Abstract. For layered InSe crystals photoluminescence spectra were investigated and the
corresponding radiative transitions were analyzed. It was found that along with the band-
to-band transitions the radiative ones with participation of impurity levels plays a
substantial role in the light emission spectrum of the semiconductor. This fact is
confirmed by the intensities of the radiative bands for the impurity level – c(v)-band
transitions and the donor-acceptor recombination. The temperature dependences of the
spectrum in the range of 100 to 300 К have also enabled to ascertain the dynamics of
these radiative transitions. At the temperatures 180 to 300 К, the bands associated with
the indirect transitions involving indirect free excitons are more intensive. At
100…180 К, the intensity of the bands corresponding to the direct transitions with
participation of direct free excitons increases. We have determined the energies of the
observed photoluminescence bands, and the band diagram of the corresponding radiative
transitions in InSe has been built.
Keywords: InSe, layered crystal, photoluminescence, energy diagram.
Manuscript received 10.10.06; accepted for publication 23.10.06.
1. Introduction
ІnSe crystals are an interesting object for optical
investigations including photoluminescence (PL)
measurements. The layered crystal structure favours to
this study allowing to easily prepare samples of arbitrary
thickness by cleaving them from an ingot. Their mirror-
like surfaces are practically ideal with a normal parallel
to the crystallographic C axis. A variety of electron
transitions determines a complicated structure of PL
spectra due to the presence of energy levels of various
nature in the InSe energy gap [1-8]. So, ІnSe is an
indirect semiconductor [9]. The presence of large
concentrations of native donors and acceptors, which
follows from compensative character of its electric
properties [10], results in the existence of corresponding
levels. The strong electron-hole interaction in the crystal
promotes the appearance of additional levels. It causes
the creation of both free and bound excitons.
An analysis of the PL spectra of layered ІnSe
crystals shows that different authors have found various
PL spectra structure and propose various interpretations
for them. It is necessary to specify that ІnSe can be
grown from both stoichiometric and nonstoichiometric
composition of melts [11]. It also can affect the quality
of the samples and the structure of PL spectra. Some
authors observed the dependence of luminescence
intensity on a method of sample preparation [3]. In a
majority of the papers, PL spectra were investigated at
the temperatures 4.2-77 K due to their weak intensity at
higher temperatures.
However, we have observed the intensive PL
spectra of ІnSe even at the room temperature. Therefore,
the task of this work was to identify radiative transitions
and to study their temperature dynamics.
2. Experimental
Indium monoselenide single crystals were grown using
the Bridgman method from a nonstoichiometric melt of
the components. This method allows to grow crystals
with a high degree of perfection. They were obtained as
ingots of 5-6 cm long and 12-14 mm in diameter. The
ingots were cut on disks of 4-5 mm in height, from
which plane-parallel samples were cleaved. 200-300 μm
plates for our measurements were chosen in such a way
to avoid their possible deformations and surface
scratches.
The PL spectra were measured using a MDR-3
diffraction monochromator. Its resolution was chosen in
such a way to have the best correlation between PL
signal intensity and resolution value. Light-emitting GaP
diodes were used as a source of continuous excitation
with a radiation wave length of 0.55 μm. The
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 4. P. 36-39.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
37
Ph
ot
ol
um
in
es
ce
ns
e
in
te
ns
ity
, a
rb
. u
ni
ts
0
2
4
6
8
1 0 2 3 5 Kb
1 1 5 1 2 0 1 2 5 1 3 0 1 3 5 1 4 0 1 4 5
0
2
4
6
8
10 205 K
c
0
2
4
6
8
1 0 1 7 5 K
d
E 1 E
0
2
4
6
8
10
12 145 KD 1 De
1 .1 5 1 .2 0 1 .2 5 1 .3 0 1 .3 5 1 .4 0 1 .4 5
0
5
1 0
1 5
10 0 K
P h o to n en e rg y , eV
f
0
2
4
6
8
1 0 2 9 5 K
A
B
C
E 1
E
a
D
Fig. 1. Photoluminescence spectra of n-InSe sample at various
temperatures.
temperature measurements of the PL spectra were
carried out in the range of 100 to 300 K in a cryostat
with an accuracy of temperature stabilization of ±0.1 К.
The spectra measurements were carried out by 30 К
steps. The PL spectra were registered using a calibrated
Si photodiode. All the spectra were corrected with
respect to the spectral sensitivity of the photodiode. The
area of the light spot on the sample surface was about
0.5 mm2.
3. Results and discussion
A typical PL spectrum of InSe at various temperatures is
shown in Fig. 1. It consists of many bands with varying
intensities. At room temperature, these bands are marked
by letters A, B, C, D, E1, and E. At certain temperatures,
the spectra are not shown owing to negligible changes in
intensities of the radiation bands and their insignificant
energy shift with lowering the temperature. The bands
A, B, and C are caused by the radiative transitions with
participation of donor and acceptor levels, because these
bands are located at the longwave spectral edge The
peaks of energy positions of these bands and their
intensities do not have pronounced temperature
dependence (Fig. 2), they also resides at these levels.
The electron transitions from the donor level ED to the
valence band correspond to the most intensive band (С)
of three observed ones (Fig. 3). The transitions from the
conduction band to the acceptor level EA correspond to
the band B (Fig. 3). Such identification of the bands is
caused by the fact that compensated InSe has the
electron conductivity. A partial compensation of the
donor levels is indicative of the less concentration of the
acceptor levels and, therefore, the transitions with
participation of the acceptor levels EA have the lower
intensity (B band) in comparison to С band. The
transitions from the donor to acceptor levels correspond
to the weakest band A.
The band D (that is the most intensive at Т = 295 K
from all the bands) corresponds to the indirect band-to-
band transitions. Such transitions occur with
participation of phonons. According to [12], the D band
intensity can be described by the equation
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡ −
−−≈
kT
Eh
EhhI
i
gi
g
)(
exp)()( 22 ν
ννν , (1)
where ν is the light frequency, h is the Plank constant,
i
gE is the indirect bandgap of InSe, k is the Boltzmann
constant, Т is the absolute temperature. The band
calculated according to relation (1) is shown in Fig. 1f
by open circles. As one can see, there is a good
agreement between the theoretical and experimental
curves. From comparison of these curves, we have
estimated that the value of i
gE at 100 К is equal to
1.27 eV. Taking into account the D band temperature
shift (Fig. 2, ∂Eg /∂T = −8.5⋅10−5 eV/К), it was found that
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 4. P. 36-39.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
38
i
gE (295 К) = 1.253 eV. The radiative spectra, attributed
to the transitions involving the donor ED and acceptor EA
levels, are determined by an equation analogous to the
equation (1) but with the energy shift by the energy
depth of these levels from the corresponding bands.
Thus, to determine the ED and EA values it is enough to
determine the energy distances between the C-D and B-
D peaks. The average values of ED and EA measured for
several samples are 0.026 and 0.060 eV, respectively.
According to [13], the photon energy of the radiative
donor-acceptor recombination (A band) is described by
the expression
r
eEEEh DA
i
g ⋅
++−=
ε
ν
2
)( , (2)
where e is the electron charge, ε is the dielectric constant
of InSe, r is the distance between the donor and acceptor
centers. With account of hν (A) = 1.206 eV and
ε = 7.36 [14], we have calculated r = 62.3 nm.
The shortwave bands E1 and E correspond to direct
band-to-band transitions. Their intensity sharply
increases with lowering temperature whereas that of the
D band one decreases. In the case of direct transitions,
the spectrum of intrinsic radiation has a form [12]:
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡ −
−−≈
kT
Eh
EhhI
d
gd
g
)(
exp)()( 2/12 ν
ννν , (3)
where d
gE is the direct bandgap. The calculated curve is
also shown in Fig. 1f. As one can see, the experimental
curve is much broader in comparison to the calculated
one. d
gE (100 К) = 1.341 eV, d
gE (295 К) = 1.324 eV.
Thus, the difference between the d
gE and i
gE values is
71 meV.
Fig. 2. Temperature shifts of the A, B, C, D, E1 and E peaks.
Fig. 3. Energy level diagram of the radiative transitions in InSe.
The temperature dependences of the bands make it
possible to establish peculiarities of D and E bands.
Their doublet character is the best expressed at 145 К
(Fig. 1e) and 175 К (Fig. 1d). The appearance of D1 and
E1 bands is caused by the electron transitions with
participation of indirect and direct free excitons from the
principal exciton state n = 1 to the valence band (Fig. 3).
Although it is known from the literature about the direct
free exciton binding energy d
XE = 14.5 meV [15], there
are no data for the indirect ones i
XE . As one can see
from the inserts d and e in Fig. 1, i
X
d
X EE > . Their
values are as follows: d
XE = 16.9 meV and i
XE =
13.0 meV. Note for comparison that the thermal energy
kT is equal to 15 and 12.5 meV at 175 and 145 К,
respectively. It is less than the binding energy of free
excitons at these temperatures and, therefore, allowed to
observe the doublet character of D and E bands. At other
temperatures, this peculiarity disappears due to changes
in the intensity of the corresponding transitions.
Note that the impurity-bound excitons define the
radiative spectra at helium temperatures. Usually, they
have weak intensity and, therefore, were not taken into
account for interpretation of the obtained spectra.
4. Conclusions
PL spectra of undoped InSe were measured within the
temperature range of 100 to 295 K. Using comparison of
the calculated and experimental spectra, we have carried
out an analysis of the radiation bands. It made possible
to determine the parameters of energy levels in InSe. We
have ascertained that at Т = 295 К the direct and indirect
energy gaps are d
gE = 1.324 eV and i
gE = 1.270 eV,
respectively. The temperature shift of the bands is
−8.5⋅10−5 eV/К. The binding energies of the free direct
and indirect excitons are d
XE = 16.9 meV and i
XE =
13.0 meV. The energy depths of the donor level below
the conduction band bottom and acceptor level above the
valence band top are ED = 26 meV and EA = 60 meV,
respectively. Distance between the donor and acceptor
centers is equal to 62.3 nm.
100 150 200 250 300
1.20
1.25
1.30
1.35
Pe
ak
e
ne
rg
y,
e
V
Temperature, K
A
B
C
D
E1
E
d
xE
E1 E DD1 C B A
E
i
xE
EV
EA
ED
EC
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 4. P. 36-39.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
39
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