Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves
Performed in this work is the research of the influence of microwave irradiation (2.45 GHz, 24 GHz) on the spectra of low-temperature (T = 2 K) photoluminescence (PL) in single crystals CdTe:Cl. The transformation of impurity-defect centers in CdTe:Cl, responsible for PL within the spectral range 1....
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| Zitieren: | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves / N.D. Vakhnyak, O.P. Lotsko, S.I. Budzulyak, L.A. Demchyna, D.V. Korbutyak, R.V. Konakova, R.A. Red’ko, O.B. Okhrimenko, N.I. Berezovska // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 2. — С. 250-253. — Бібліогр.: 7 назв. — англ. |
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| author | Vakhnyak, N.D. Lotsko, O.P. Budzulyak, S.I. Demchyna, L.A. Korbutyak, D.V. Konakova, R.V. Red’ko, R.A. Okhrimenko, O.B. Berezovska, N.I. |
| author_facet | Vakhnyak, N.D. Lotsko, O.P. Budzulyak, S.I. Demchyna, L.A. Korbutyak, D.V. Konakova, R.V. Red’ko, R.A. Okhrimenko, O.B. Berezovska, N.I. |
| citation_txt | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves / N.D. Vakhnyak, O.P. Lotsko, S.I. Budzulyak, L.A. Demchyna, D.V. Korbutyak, R.V. Konakova, R.A. Red’ko, O.B. Okhrimenko, N.I. Berezovska // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 2. — С. 250-253. — Бібліогр.: 7 назв. — англ. |
| collection | DSpace DC |
| container_title | Semiconductor Physics Quantum Electronics & Optoelectronics |
| description | Performed in this work is the research of the influence of microwave irradiation (2.45 GHz, 24 GHz) on the spectra of low-temperature (T = 2 K) photoluminescence (PL) in single crystals CdTe:Cl. The transformation of impurity-defect centers in CdTe:Cl, responsible for PL within the spectral range 1.3 to 1.5 eV under microwave irradiation, was analyzed. The parameter of electron-phonon interaction (Huang–Rhys factor) for the donor-acceptor PL band, which depends on the time of microwave irradiation, has been calculated.
|
| first_indexed | 2026-03-21T11:50:46Z |
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 2. P. 250-253.
doi: https://doi.org/10.15407/spqeo20.02.250
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
250
PACS 78.55.Hx, 78.70.Qq
Transformation of impurity-defect centers in single crystals CdTe:Cl
under the influence of microwaves
N.D. Vakhnyak1, O.P. Lotsko1, S.I. Budzulyak1, L.A. Demchyna1, D.V. Korbutyak1, R.V. Konakova1,
R.A. Red’ko1, O.B. Okhrimenko1, N.I. Berezovska2
1V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, prospect Nauky, 03680 Kyiv, Ukraine
Corresponding author e-mail: div47@isp.kiev.ua
2Taras Shevchenko National University of Kyiv, Physics Department,
64/13, Volodymyrska str., 01601 Kyiv, Ukraine
Abstract. Performed in this work are the researches of the influence of microwave
irradiation (2.45 GHz, 24 GHz) on spectra of low-temperature (T = 2 K)
photoluminescence (PL) in single crystals CdTe:Cl. Transformation of impurity-defect
centers in CdTe:Cl responsible for PL within the spectral range 1.3 to 1.5 eV under
microwave irradiation was analyzed. The parameter of electron-phonon interaction
(Huang–Rhys factor) for the donor-acceptor PL band, which depends on the time of
microwave irradiation, has been calculated.
Keywords: photoluminescence, microwave irradiation, Huang–Rhys factor, donor-
acceptor pair, impurity-defect center.
Manuscript received 25.01.17; revised version received 26.04.17; accepted for
publication 14.06.17; published online 18.07.17.
1. Introduction
High-resistant single crystal CdTe is a promising
material for manufacturing uncooled detectors of X- and
γ-radiation [1, 2].
Despite that prospects of CdTe-detectors was
repeatedly confirmed, technological difficulties
associated with the cultivation of high-quality single
crystals of large diameter hinder their widespread
implementation. Only the system control and detailed
studying the physical, technological and chemical
processes that take place from crystal growth to their
operation as detectors could provide maximum results to
radio-ecological monitoring of individual objects and
space exploration as well. Note that the influence of
external factors on the impurity-defect structure of high-
resistant CdTe single crystals is studied to find cheap
and technologically simple external treatments that
improve the detector material. Also important there is
the study of stability and transformation of impurity-
defect complexes in single crystals CdTe:Cl influenced
by technological processing.
For single crystals CdTe:Cl, there is some progress
in studying the nature of defects and in research the
influence of external factors on transformation of
impurity-defect state of this material, but the question of
optimization of technology, both growing and
technological treatments, remains open and requires
further research [1, 3]. It contains determining the
dominant mechanisms of transformation, thermal and
radiation stability of impurity-defect centers, accounting
and use of which is very important and often decisive in
the development and optimization of manufacturing
detectors of X- and γ-radiation based on single crystals
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 2. P. 250-253.
doi: https://doi.org/10.15407/spqeo20.02.250
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
251
CdTe:Cl. Thus, the study of mechanisms responsible for
transformation of complexes of defects in these single
crystals under various technological processing and
expanded search for optimal regimes capable to improve
the structure of this material is very important and
topical. If during radiation and thermal processing the
mechanism of interaction of external factors of
semiconductor material is understandable and
predictable, so using the microwave radiation to modify
impurity-defect state requires further research and
analysis of the data necessary to determine the nature of
observed transformations in these cases.
This paper presents the results of researching the
influence of microwave irradiation of single crystals
CdTe:Cl (frequencies 2.45 and 24 GHz) on the spectra
of their photoluminescence at the low temperature (T =
2 K). The features of transformation of impurity-defect
complexes within the spectral range 1.3…1.5 eV after
microwave treatment have been analyzed.
2. Experimental technique
The investigated single crystals CdTe:Cl were grown
using the Bridgman method. Chlorine doping was
performed during crystal growth. For this purpose, the
ampoule from carbonated silica (diameter 15 mm) filled
with synthesized cadmium telluride (pre-cleared by
vertical zone melting) and by pre-determined amount of
salt CdCl2. Before growing, the ampoule was maintained
under melt temperatures reaching the plateau of tubular
oven ones (T = 1390 K) for 4 hours. And then, it was put
down through the temperature gradient of 10…12 K/cm
with the speed 4.8 mm/h. After the growing process, the
ampoule was cooled by putting down through the
temperature gradient 50 K/cm. The concentration of
chlorine injected impurity in the grown crystals was
5⋅1017 and 5⋅1019 cm–3.
Microwave irradiation of crystals was held in
gyrotron complex for microwave processing the
materials at the frequencies 2.45 and 24 GHz.
The total time of exposure was a sum of partial
irradiation times of 5 s with intervals between irradiation
steps in 3 min. Measurements showed that, in every
process of radiation, temperature changes did not exceed
2 °C as compared to the initial temperature of the
sample. For researching the luminescent properties, we
used the crystals CdTe:Cl irradiated at different
exposures: 5, 10, 60, 120 and 180 s. After each session
of achievement the required dose of microwave
irradiation, PL spectra were measured.
The measurements were performed within the
range 1.3…1.5 eV at the temperature 2 K, which was
provided by helium vapor pumping out from the cryostat
by using a computerized system based on
monochromator MDR-3 (inverse linear dispersion
2.6 nm/mm). As a source of excitation radiation, the
continuous argon Ar+ laser with the wavelength
514.5 nm was used.
To characterize the degree of electron-phonon
interaction, the factor by Huang–Rhys S was used, it was
determined using the PL spectra. It reflects the
probability of radiative transitions in impurity centers
with participation of LO-phonons. Being based on the
model [4] S is a function of the distance R between the
components of donor-acceptor pair (DAP). Therefore,
changes in impurity-defect structure of the samples
caused by the microwave treatment are appropriately
reflected by changes of the Huang–Rhys factor.
3. Experimental results and discussion
Fig. 1 shows the measured PL spectra of CdTe:Cl within
the range 1.3…1.5 eV. For comparison, brought also are
PL spectra of undoped CdTe. To investigate the nature
of this band, a lot of work was made, but for a long time
could not explain all the features of its behavior. Since
the beginning of the study of CdTe photoluminescence,
it was clear that the band in the vicinity of 1.45 eV is
associated with radiative recombination of DAP with
longitudinal optical phonons, as evidenced by the regular
repetition of the enough intense zero-phonon line (the
distance between the maxima that corresponds to the
longitudinal optical phonon energy in millielectron-
volts). Analyzing the intensity ratio for the phonon
replicas can define the constant of electron-phonon
interaction for the radiative center. But the nature of the
zero-phonon line as well as its exact position in the
power scale is still differently interpreted and defined in
the works of different authors. This shows that in reality
luminescence in this spectral region is likely combined,
which is conditioned by superposition of the emission
spectra of several centers of different nature, and thus, to
properly determine the characteristics of the electron-
phonon interaction, it is necessary to account for this
effect.
1.35 1.38 1.41 1.44 1.47 1.50
CdTe:Cl
CdTe
3LO
2LO
1LO
ZPL
Y
P
L
in
te
ns
ity
, a
rb
. u
n.
Energy, eV
Fig. 1. Spectrum of CdTe undoped and doped with chlorine
(NCl = 5⋅1019 cm–3) within the range 1.3…1.5 eV.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 2. P. 250-253.
doi: https://doi.org/10.15407/spqeo20.02.250
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
252
From the short edge, there is the so-called Y-band
(Emax = 1.478 eV). At first sight, it could be associated
with zero-phonon line (ZPL) radiation involving A-cen-
ters (DAP consisting of acceptor vacancy of metal and do-
nor impurity), because the energy distance from it to the
next peak of the PL side (Emax ≈ 1.455 eV) approximately
coincides with the energy of the longitudinal optical
phonons in CdTe. However, this band has very unusual
features for the deep recombination centers and has a
relatively wide ZPL and weakly expressed long-wave tail
of phonon replicas, which is the feature inherent to
extended defects in recombination [4] and can be related
to recombination of excitons bound to dislocations [5].
Let’s analyze the shape of structured PL band
observed in single crystals CdTe:Cl within the range
1.3…1.5 eV. As noted above, the indicated PL band is a
complex that includes the line of D-A transitions
involving A-center with LO-phonon repetitions and Y-
phonon line with its repetitions as well. Therefore, for
the correct analysis the shape of specified band needs to
be decomposed into two components.
Example of description of the experimental PL
spectrum by superposition of two lines (Y-line and
DAP), which are characterized by different energy
positions and different values of S, is shown in Fig. 2.
Satisfactory adjustment of the experimental PL band
shape to the total intensity of two estimated series was
achieved by using S and the decay parameter Γ as fitting
parameters. The energy positions of zero-phonon lines
for two series and the value of LO-phonon energy
remained unchanged.
The detailed analysis of PL band shape for DAP
allowed to ascertain that the Huang–Rhys factor S that
characterizes the degree of electron-phonon interaction
in DAP, depending on the concentration of introduced
impurities, changes from S = 1.68 (for NCl = 5⋅1017 cm–3)
to S = 1.5 (for NCl = 5⋅1019 cm–3). Thus, the increase in
the impurity concentration of chlorine results in reducing
the distance between donors and acceptors and causes
the corresponding reduction of the Huang–Rhys factor.
The physical reason of reduction of this factor when
decreasing the distance between donors and acceptors is
growing mutual compensation of charge distributions for
these centers as well as the corresponding decrease in
deformation shift of the centers relatively to their posi-
tions in the configurational space in the absence of
carriers capture. The second reason of S value decrease
with increasing the impurity concentration of chlorine in
the samples may be higher number of defects in CdTe:Cl
single crystals, which shield Coulomb interaction in DAP.
Microwave irradiation at the frequency 24 GHz for
5 s did not lead to significant changes in the observed PL
spectrum. However, under further exposure of the
samples by microwaves, the spectral dependence was af-
fected. With increasing duration of microwave irradia-
tion, the intensity of Y-PL band decreases. This may
indicate a decrease in the concentration of longitudinal
defects, on which excitons bind in subsurface crystal
region under microwave radiation. These changes are
typical for the single crystals CdTe:Cl subjected to
~200 °C thermal annealing [6].
Changes in the ratio of intensities of the observed
phonon replica lines of the PL spectrum of single
crystals CdTe:Cl are apparently caused by transforma-
tion of donor-acceptor centers under microwave
treatment with possible changes in their concentration
and, consequently, in the distance between donors and
acceptors. The latter should lead to a corresponding
change in the Huang–Rhys factor value.
For a detailed analysis of the low temperature PL
of these crystals within the energy range 1.3 to 1.5 eV
after microwave irradiation, we made decomposition of
PL spectra (similar to that shown in Fig. 2). It consists of
two bands: 1.455 eV – radiative recombination due to
DAP (1.470–1.478 eV) and the Y-band with relevant
phonon repetitions. Analyzing every curve and calcula-
ting Huang–Rhys factor for each one, it was obtained
that in the initial state for Y-band (SY = 0.88), this pa-
rameter was significantly less than the same denotation
for DAP involving A-center (SDAP = 1.50). Thus, SY was
practically unchanged and SDAP grew in the range of
1.50…1.71 with increasing duration of microwave
irradiation of single crystals CdTe:Cl (Table).
The latter may be due to the increasing distance
between donors and acceptors and different effects of
microwave radiation on the concentration of
nonradiative recombination centers and DAP in near-
surface field of single crystals. Microwave processing of
the samples at the frequency 2.45 GHz, as shown in [7],
led to lower values change of the Huang–Rhys factor
(from 1.50 to 1.64) than for the 24 GHz frequency. The
latter obviously suggests less intense transformation of
defect centers at a lower frequency, as the microwave
power density in both cases was the same.
1.35 1.40 1.45 1.50
P
L
in
te
ns
ity
, a
rb
. u
n.
4LO
3LO
2LO
1LO
ZPL
Y
Еnergy, eV
CdTe:Cl
NCl=5·1019 cm-3
Fig. 2. Decomposition of the experimental PL spectrum (solid
line) into two components: DAP (points) and Y-line (dashed
line) with their phonon repetitions.
Table. Change in the Huang–Rhys factor value due to
microwave treatment.
ttreat Starting position 10 s 60 s 120 s
SDAP 1.50 1.58 1.68 1.71
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 2. P. 250-253.
doi: https://doi.org/10.15407/spqeo20.02.250
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
253
0 30 60 90 120 150 180
1.5
1.6
1.7
treated with 24 GHz
treated with 2.45 GHz
S D
AP
Total time of treatment, s
Fig. 3. Dependence of the Huang–Rhys factor on the duration
of the microwave treatment of single crystals CdTe:Cl with
NCl = 5⋅1019 cm–3 at the frequencies 2.45 and 24 GHz. Points –
experiment, the line – approximation using Eq. (1).
Using the equation of the following form:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
−−=
B
t
ASS treat
m exp , (1)
where Sm is the value of Huang–Rhys factor, ttreat – du-
ration of microvawe treatment, A and B are empirical
constants. Using the least squares method, we were able
to approximate experimental dependence S(ttreat) with
parameters Sm
(24 GHz) = 1.7, A(24GHz) = 0.20,
B(24GHz) = 22.92; Sm
(2.45GHz) = 1.63, A(2.45GHz) = 0.13,
B(2.45GHz) = 7.36 for the experimental data, corresponding
treatments at the frequencies 24 and 2.45 GHz,
respectively (Fig. 3).
4. Conclusions
Performed in this paper researches of the effect of
microwave irradiation on the PL spectra of CdTe:Cl
within the range 1.3…1.5 eV are indicative of
modification of defect structure in the irradiated
material. The microwave treatment duration ≥10 s leads
to the increase in the distance between components of
DAP responsible for the recombination radiation near
1.455 eV. This conclusion has been obtained after
analyzing the theoretical calculations concerning the
changes of the Huang–Rhys factor for DAP band and
has been confirmed experimentally by observation of the
long wave shift of the PL peak. It has been obtained that
the microwave treatment leads to quenching the band
near 1.478 eV associated with extended defects, which
indicates effective interaction of microwave fields with
dislocations of the corresponding nature. The data
obtained in this work together with the results [7]
evidence that increase in the dose of microwave
irradiation and frequency of the used wavelengths
enhance the observed effect.
References
1. Korbutyak D.V., Melnychuk S.V., Korbut E.V.,
Borysiuk M.M. Cadmium Telluride: Impurity-
Defect States and Detector Properties. K.: “Ivan
Fedorov”, 2000. 198 p. (in Ukrainian).
2. Korbutyak D.V., Venger E.F., Krylyuk S.G. et al.
Detectors of X- and γ-radiation on the base of
CdTe and CdZnTe single crystals (Review).
Optoelectronics and semiconductor technics. 2001.
36. P. 5–34 (in Russian).
3. Komar’ V.K., Puzykov V.M. Single Crystals of
AIIBVI Group. Growth, Properties, Application.
Khar’kov, Institute of Single Crystals, 2002. 244 p.
(in Russian).
4. Korbutyak D.V., Lotsko A.P., Vakhnyak N.D.,
Demchyna L.A., Konakova R.V., Milenin V.V.,
Red’ko R.A. Effect of microwave irradiation on the
photoluminescence of bound excitons in CdTe:Cl
single crystals. Semiconductors. 2011. 45, No. 9. P.
1175–1181.
5. Dean P.J., Williams G.M., Blackmore G. Novel
type of optical transition observed in MBE grown
CdTe. J. Phys. D. 1984. 17, No. 8. P. 2291–2300.
6. Korbutyak D.V., Lots’ko O.P., Vakhnyak N.D.,
Demchyna L.A. Diagnostic of donor-acceptor pairs
in CdTe:Cl single crystals. Naukovyi visnyk
KUEITU: Novi tekhnologii. 2010. № 2(28). P. 8–12
(in Ukrainian).
7. Budzulyak S.I., Korbutyak D.V., Lotsko A.P. et al.
Features of transformation of impurity-defect
complexes in CdTe:Cl under the influence of
microwave irradiation. Tekhnologiya i konstruiro-
vanie v elektronnoi_apparature. 2014. №4. P. 45–
49 (in Russian).
|
| id | nasplib_isofts_kiev_ua-123456789-214923 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1560-8034 |
| language | English |
| last_indexed | 2026-03-21T11:50:46Z |
| publishDate | 2017 |
| publisher | Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| record_format | dspace |
| spelling | Vakhnyak, N.D. Lotsko, O.P. Budzulyak, S.I. Demchyna, L.A. Korbutyak, D.V. Konakova, R.V. Red’ko, R.A. Okhrimenko, O.B. Berezovska, N.I. 2026-03-04T12:48:26Z 2017 Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves / N.D. Vakhnyak, O.P. Lotsko, S.I. Budzulyak, L.A. Demchyna, D.V. Korbutyak, R.V. Konakova, R.A. Red’ko, O.B. Okhrimenko, N.I. Berezovska // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 2. — С. 250-253. — Бібліогр.: 7 назв. — англ. 1560-8034 PACS: 78.55.Hx, 78.70.Qq https://nasplib.isofts.kiev.ua/handle/123456789/214923 https://doi.org/10.15407/spqeo20.02.250 Performed in this work is the research of the influence of microwave irradiation (2.45 GHz, 24 GHz) on the spectra of low-temperature (T = 2 K) photoluminescence (PL) in single crystals CdTe:Cl. The transformation of impurity-defect centers in CdTe:Cl, responsible for PL within the spectral range 1.3 to 1.5 eV under microwave irradiation, was analyzed. The parameter of electron-phonon interaction (Huang–Rhys factor) for the donor-acceptor PL band, which depends on the time of microwave irradiation, has been calculated. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves Article published earlier |
| spellingShingle | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves Vakhnyak, N.D. Lotsko, O.P. Budzulyak, S.I. Demchyna, L.A. Korbutyak, D.V. Konakova, R.V. Red’ko, R.A. Okhrimenko, O.B. Berezovska, N.I. |
| title | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves |
| title_full | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves |
| title_fullStr | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves |
| title_full_unstemmed | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves |
| title_short | Transformation of impurity-defect centers in single crystals CdTe:Cl under the influence of microwaves |
| title_sort | transformation of impurity-defect centers in single crystals cdte:cl under the influence of microwaves |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/214923 |
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