Nanograin boundaries and silicon carbide photoluminescence
The luminescence spectra of SiC crystals and films with grain boundaries (GB) on the atomic level were observed. The GB spectra are associated with luminescence centers localized in areas of specific structural abnormalities in the crystal, without reference to the one-dimensional layer-disordering....
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2017
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| Zitieren: | Nanograin boundaries and silicon carbide photoluminescence / S.I. Vlaskina, G.N. Mishinova, V.I. Vlaskin, V.E. Rodionov, G.S. Svechnikov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 3. — С. 344-348. — Бібліогр.: 12 назв. — англ. |
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| author | Vlaskina, S.I. Mishinova, G.N. Vlaskin, V.I. Rodionov, V.E. Svechnikov, G.S. |
| author_facet | Vlaskina, S.I. Mishinova, G.N. Vlaskin, V.I. Rodionov, V.E. Svechnikov, G.S. |
| citation_txt | Nanograin boundaries and silicon carbide photoluminescence / S.I. Vlaskina, G.N. Mishinova, V.I. Vlaskin, V.E. Rodionov, G.S. Svechnikov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 3. — С. 344-348. — Бібліогр.: 12 назв. — англ. |
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| container_title | Semiconductor Physics Quantum Electronics & Optoelectronics |
| description | The luminescence spectra of SiC crystals and films with grain boundaries (GB) on the atomic level were observed. The GB spectra are associated with luminescence centers localized in areas of specific structural abnormalities in the crystal, without reference to the one-dimensional layer-disordering. The zero-phonon part of GB spectra is always within the same energy range (2.890…2.945 eV) and does not fit in the dependence of its position in the energy scale on the percent of hexagonality, as in the case of stacking faults (SFᵢ) and deep level (DLᵢ) spectra. The zero-phonon part 2.945…2.890 eV with a fine structure is better observed in crystals with the centers of origin growth of the crystal, if Nᴰ – Nᴬ ~ (2…8)·10¹⁶ cm⁻³, ND ~ (2…7)·10¹⁷ cm⁻³. The edge phonons of the Brillouin zone TA-46 meV, LA-77 meV, TO-95 meV, and LO-104 meV are involved in the development of the GB spectrum. This spectrum may occur simultaneously with the DLᵢ and SFᵢ ones. The GB spectra also occur after high-temperature processing of the β-phase (in the 3C-SiC) with the appearance of the α-phase. The temperature range of observation is 4.2…40 K. There is synchronous thermal quenching of all elements in the fine structure. The thermal activation energy of quenching is Еₐᵀ ~ 7 meV.
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 3. P. 344-348.
doi: https://doi.org/10.15407/spqeo20.03.344
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
344
PACS 64.70.K-, 77.84.Bw, 81.30.-t
Nanograin boundaries and silicon carbide photoluminescence
S.I. Vlaskina1, G.N. Mishinova3, V.I. Vlaskin4, V.E. Rodionov5, G.S. Svechnikov2
1Yeoju Institute of Technology (Yeoju University),
338, Sejong-ro, Yeoju-eup, Yeoju-gun, Gyeonggi-do, 469-705 Korea, e-mail: businkaa@mail.ru
2 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”
Av.Pobedi 37, Kyiv, Ukraine,
3Taras Shevchenko Kyiv National University, 64, Volodymyrs’ka str., 01033 Kyiv, Ukraine
4Sensartech, 2540 Lobelia Dr., Oxnard, 93036 California, USA
5State Institution "Institute of Environmental Geochemistry, NAS of Ukraine"
av. Academician Palladin, Kyiv 34a
Abstract. The luminescence spectra of SiC crystals and films with grain boundaries
(GB) on the atomic level were observed. The GB spectra are associated with
luminescence centers localized in areas of specific structural abnormalities in the crystal,
without no reference to the one-dimensional layer-disordering. The zero-phonon part of
GB spectra is always within the same energy range (2.890…2.945 eV) and does not fit in
the dependence of its position in the energy scale on the percent of hexagonality as in the
case of stacking faults (SFi) and deep level (DLi) spectra. The zero-phonon part
2.945…2.890 eV with a fine structure is better observed in crystals with the centers of
origin growth of crystal, if ND – NA ~ (2…8)·1016 cm–3, ND ~ (2…7)·1017 cm–3. The edge
phonons of the Brillouin zone TA-46 meV, LA-77 meV, TO-95 meV and LO-104 meV
are involved in development of the GB spectrum. This spectrum may occur
simultaneously with the DLi and SFi ones. The GB spectra also occur after high
temperature processing the β-phase (in the 3C-SiC) with appearance of the α-phase. The
temperature range of observation is 4.2…40 K. There is synchronous thermal quenching
of all elements in the fine structure. The thermal activation energy of quenching is
ЕаТ ~ 7 meV.
Keywords: silicon carbide, nanocrystalline film, luminescence, grain boundaries.
Manuscript received 03.05.17; revised version received 01.08.17; accepted for
publication 06.09.17; published online 09.10.17.
1. Introduction
Silicon carbide is a wide bandgap indirect
semiconductor with variety of polytypes. Experimental
results and theoretical calculations showed that the
luminescence of different polytypes strongly influenced
by defects [1-3]. The luminescence spectra [4, 5] of SiC
crystals and films with stacking faults (SFi) in high-
purity SiC [2] and with deep level (DLi) [6-9] in lightly
doped SiC reflect formation of intermediate metastable
phases during 3C↔6H transitions. SFi and DLi spectra
hand-in-hand follow the structure transformations.
Grain boundaries in silicon carbide produced by
sublimation were examined using high resolution
transmission electron microscope (HRTEM) [6]. 6H-SiC
polytype boundary parallel to (0001) and 6H/15R
hetero-polytype boundary with a thickness on the atomic
level were observed. But luminescence of these defects
was not investigated. Therefore, it is very important to
investigate the grain boundaries (GB) by using optical
methods.
Nowadays, since SiC thin films and crystals are
widely used to fabricate devices, it is essential to
understand properties of grain boundaries that can
decrease the efficiency of these devices.
The purpose of this work is to decode the structure
of low-temperature luminescence spectra in SiC crystals
and in films with GB.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 3. P. 344-348.
doi: https://doi.org/10.15407/spqeo20.03.344
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
345
2. Experimental results and discussion
We studied low temperature spectra by using techniques
described early [7]. For this experiment, we selected
lumpy, blocky SiC crystals and crystals with steps of
growth. The same type of spectra (GB) was observed, if
crystals had block’s disorientation in a basal plane (not
only along the c axis). GB spectra are shown in Fig. 1
for the case when blocks have a common axis c, but
were disoriented in the basal plane. Such GB spectrum is
not observed in the thin plate-like crystals (not lumpy,
not blocky crystals).
The low temperature photoluminescence spectrum
of the SiC crystal which has blocks disoriented in the
basal plane (concentration ND – NA ~ 3·1016 cm–3, sample
N2DL) with GB spectrum at 4.2 ° K is shown in Fig. 1.
Thus, after detection of SFi and DLi spectra and
their careful investigations [10-12], we found another
new spectrum, which zero-phonon line had been
allocated at 2.890…2.945 eV (the so-called GB
spectrum) (Fig. 1). This spectrum, like to the cases of
SFi and DLi spectra, clearly shows the fine structure. The
GB spectrum was observed only in pure crystals, when
the concentration of non-compensated impurities was
ND – NA ~ (2…9)·1016 cm–3.
Fig. 2 shows the zero-phonon structure of the GB
spectrum for different crystals of DLi (Fig. 2a) and SFi
series (Fig. 2b). It can be seen that GB spectrum is very
structured (see inset in Fig. 2a, where one segment
equals 1 meV). The slit width (equal to 0.5 meV) yields
to the detailed spectrum fractures and allowed to see the
fine structure. In the particular case (sample N14DL), the
nature of GB spectrum is maximally manifested. The
inset (Fig. 2a) shows an enlarged part of the zero-phonon
GB spectrum (photoluminescence (PL) and
phosphorescence (PS)) for the sample N2DL with
ND – NA ~ 2·1016 cm–3 and for the sample N4DL with
ND – NA ~ 8·1016 cm–3. We studied two polar faces of the
crystals: ( 1000 ) and ( 0001). The chain curve 1 at the
inset in Fig. 2a shows photoluminescence of the lumpy
side of the crystal (there are a spiral, stage); the dashed
curve 2 is PL of the mirror part of the crystal. Thus,
graphs show GB spectra consisting of two bands.
In the very pure or perfect crystals (where there is
only a spiral of growth, and there are no inconsistent
borders), the GB spectrum does not exist. For example
in the sample N1DL [7], there was only a spiral of growth
without grains, and there were no GB spectra. Also, we
could not find the GB spectrum, if the acceptor impurity
was less or of the order of 1016 cm–3, and donor impurity
was less than or of the order of 1016 cm–3 (i.e., if there
was not practical compensation, and samples really were
very pure). The new GB spectrum was clearer
pronounced in SFi series just because compensation of
the impurities in this series is virtually absent – there
was a very low concentration of the acceptor impurity.
Fig. 1. GB type photoluminescence spectra of the sample N2DL
with ND – NA ~ 3·1016 cm–3 at 4.2 K.
Plastic deformation was also carried out (Fig. 2c).
Redistribution of the intensities in the structural part of
the GB spectrum takes place like to that in the case of
CdS. That is, when silicon carbide crystal was
undergone to a large bend (twisted into a ram’s horn),
the island of the silicon carbide crystal (or its piece)
became a kind of direct-gap band semiconductor (as it
lifted the ban because of the phonons). It means that in
this island phonon is not required, and there takes place
the zero-phonon transition. (This is the same as in CdS.)
In crystals with the impurity concentration
ND – NA > 3·1017 cm–3, ND > 1018 cm–3 (Fig. 3), GB
spectra was not seen since refers to shallow levels of
luminescence centers, like to SFi spectrum. GB range
can be observed simultaneously with those of SFi and
DLi spectrum in impurity conditions (a) and (b) – Table
(Fig. 3).
So, in case of GB spectra (similar to the case of
DLi and SFi) the fine structure has allowed to define the
boundaries of the zero-phonon part of the spectrum. GB
have a line structure with the same density, stockade,
which were observed in [11]. It indicates that the GB
spectra represent incoherent boundaries. The GB spectra
reflect locations of two matrices docking (the side
mosaic’s docking). Literally, it’s non-compliance of the
border (border inconsistencies in films). The rest part of
the spectrum is described by involving phonon replicas
at the edge of the Brillouin zone TA-46, LA-77, TO-95
and LO-104 meV, like to the other shallow centers (as in
SFi). But, unlike SFi spectra, availability of non-phonon
part here (in GB) in explicit manifestation indicates
luminescence center locality rather than ply, extended
character inherent to SFi centers.
The temperature range of existence of the GB
center (4.2…40 K) is similar to the shallow SFi-centers.
The dependence of the GB spectra appearance
(Fig. 3) on the degree of structural disorder δ-I, δ-II is
sometimes observed and sometimes is not observed.
Therefore, we can say that the dependence on the degree
of structural disorder is not fixed.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 3. P. 344-348.
doi: https://doi.org/10.15407/spqeo20.03.344
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
346
a)
b)
c)
Fig. 2. The zero-phonon structure of the GB spectrum for different crystals: a) DLi series for samples with ND–NA ~
(2…8)·1016 cm–3, NA~ (2…7)·1017 cm–3. The inset shows an enlarged part of the zero-phonon GB spectrum (photoluminescence
(PL) and phosphorescence (PS), τ = 3 ms) for the sample N2DL with ND–NA ~ 2·1016 cm–3 and for the sample N4DL with ND–NA ~
8·1016 cm–3 from two polar faces of the crystal ( 1000 ) and ( 0001). The line 1 describes photoluminescence of the other side of
the crystal (lumpy), where there is a spiral, stage; 2 – PL of the mirror part of the crystal. b) SFi series for most pure samples with
ND–NA ~ (4…9)·1016 cm–3, NA < (1…3)·1016 cm–3. c) GB spectrum (1) before plastic deformation (PD) and (2) after plastic
deformation (PD) combined with (3) calculated the zero-phonon part of the SFi spectrum [6].
Fig. 3. Low-temperature photoluminescence spectra according to the structural imperfection and impurity concentration in SiC
crystals and films. Zero-phonon parts: SF1 – 2.853…2.793 eV, DL1 – 2.730…2.625 eV, GB – 2.945…2.890 eV. a) Pure SiC
crystals and films with non-compensated concentration ND–NA ~ (4…9)·1016 cm–3, NA ~ (1…3)· 1016 cm–3; b) lightly doped
samples with ND–NA ~ (2…8)·1016 cm–3, ND ~ (2…7)·1017 cm–3; c) doped samples with ND–NA > 3·1017 cm–3, ND > 1019 cm–3.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 3. P. 344-348.
doi: https://doi.org/10.15407/spqeo20.03.344
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
347
The impurity concentration in the crystal affects the
appearance and manifestation of the GB spectrum. If the
impurity concentration is low in pure samples (Fig. 3a),
the fine structure in the GB spectrum is generally
observed, but it is weakly pronounced. With impurity
concentration increase (Fig. 3b), the GB spectrum is
more pronounced, and there is a clear expression of the
fine structure in the spectrum. In the heavily doped
crystals, the GB range is not observed (Fig. 3c).
Thus, GB spectra can be observed simultaneously
with the SFi and DLi spectra in the case of pure and
lightly doped crystals (a) and (b) in Fig. 3. In the heavily
doped crystals (Fig. 3c), GB spectra are not observed.
The zero-phonon spectrum part of GB is located at
the energy of 2.95…2.89 eV and has the most pronoun-
ced fine structure in the case of lightly doped crystals
(Fig. 3b). The maximum resolution of the fine structure
in the spectra of GB is defined as ΔH = 0.5 meV (equal
to half-width of the fine-structure elements).
The GB spectrum is shown through interaction
with edge phonons TA-46, LA-77, TO-95, LO-104 meV
within the temperature range (4.2…40 K). As the tempe-
rature increases, synchronous thermal decay of all ele-
ments of the fine structure is observed. The thermal acti-
vation energy of extinguishing is equal to Еa
Т = 7 meV.
The dependence of the luminescence intensity on
the excitation light intensity is expressed as ,α
exclum II =
α = 0.7. (Radiation of high-pressure mercury lamp was
varied in the range of two orders of magnitude.) There is
a differentiated change in the intensity of the fine
structure. Namely, the short-wave part of the thin
structure decreases quickly.
Luminescence intensity distribution (Ilum) on the
elements of the fine structure is the same as at τ = 3 ms
in the attenuation at Iexc = 0.004 I0. (The energy Eexc is
higher than that or equal to 3.05 eV.)
Character of change in the damping (with different
delay times τ) in the afterglow in the range of
τ = 3…15 ms is I = I0 τ–α.
Values of α are the same as in the case of DLi, for
the same range of τ [8]. Also, there is a differentiated
variation of the fine structure intensity. Namely, the
short-wave part falls faster.
Maximal total intensity of the GB spectrum
decrease takes place, if excitation light polarization is
parallel to the c axis of the crystal. Thus, the
luminescence intensity decreases with polarization of the
exciting light parallel to the c axis.
Plastic deformation of the crystal (three-point
bending) stimulates the appearance of the GB spectrum
or strengthening the existed GB spectrum. Plastic
deformation of SFi series, having initially GB range,
amplifies them or stimulates their appearance. There is
redistribution of the intensities in the fine structure in
pure crystals (Fig. 3a). Namely, the intensity of the most
short-wave part of the spectrum is noticeably reduced. In
cubic β-SiC crystals, we observed occurrence of GB
spectra after high temperature annealing.
3. Conclusion
By comparing the spectra SFi, DLi and GB in different
conditions of registration and after various treatments of
the crystal we can make the following conclusions.
1. Behavior of SFi, DLi and GB spectra is different.
The zero-phonon part of GB spectrum does not follow
restructuring of the crystal. The zero-phonon part of GB
spectra does not fit in the dependence of its position in
the energy scale on the percent of hexagonally as in the
cases of SFi and DLi spectra. GB spectra are always in
the same energy range (2.890…2.945 eV). It indicates
that the GB spectra are characteristic for the grain
boundaries. In the whole, mosaic interphase
transformation of the GB spectra reflects the grain,
interlayer boundaries in SiC crystals and films. The GB
spectra are associated with luminescence centers
localized in areas of specific structural abnormalities of
the crystal, without no reference to the one-dimensional
layer disordering (as SFi and DLi).
2. The GB spectra are the most intense and structu-
rally expressed in crystals of DLi series in samples with
a lumpy growth terraces (staggered) from several cen-
ters. The GB spectra are observed in crystals with certain
structural requirements and the impurity situation ND –
NA ~ (4…9)·1016 cm–3, NA ~ (1…3)·1016 cm–3; and
especially in lightly doped samples with ND – NA ~
(2…8)·1016 cm–3, ND~(2…7)·1017 cm–3. In the case of
doped samples with ND – NA > 3·1017 cm–3, ND > 1019
cm–3, the GB spectra are not observed (Fermi level is
raised). These spectra may occur simultaneously with
the DLi spectra and SFi spectra. GB spectra also occur
after high temperature processing of β-phase (in the 3C-
SiC), with appearance of the α-phase, but much lower
intensity with weak fine structure.
3. There observed is the zero-phonon part
2.945…2.890 eV with a fine structure. The edge
phonons of the Brillouin zone TA-46 meV, LA-77 meV,
TO-95 meV and LO-104 meV are involved in the
development of the GB spectrum. The zero-phonon part
2.945…2.890 eV with a fine structure (in DLi series of
crystals) is better pronounced in crystals with the centers
of origin growth of crystal with ND – NA ~
(2…8)·1016 cm–3, ND ~ (2…7)·1017 cm–3.
4. The temperature range of observation is
4.2…40 K, i.e. about the same as in the case of part SF-
II of calculated SFi zero-phonon [6]. There is a
synchronous thermal quenching of all elements of the
fine structure. The thermal activation energy of
quenching is ЕаТ ~ 7 meV (it also coincides with the SF-
II part of calculated zero-phonon of SFi [6]).
5. Plastic deformation of the crystal (three-point
bending) stimulates appearance of GB spectra. Plastic
deformation of SFi series crystals, having initially GB
range, strengthens the GB spectra. There is redistribution
of the intensities in the fine structure. The intensity of
the most short-wave part of the spectrum is noticeably
reduced.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 3. P. 344-348.
doi: https://doi.org/10.15407/spqeo20.03.344
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
348
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|
| id | nasplib_isofts_kiev_ua-123456789-214947 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1560-8034 |
| language | English |
| last_indexed | 2026-03-21T14:44:54Z |
| publishDate | 2017 |
| publisher | Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| record_format | dspace |
| spelling | Vlaskina, S.I. Mishinova, G.N. Vlaskin, V.I. Rodionov, V.E. Svechnikov, G.S. 2026-03-05T12:02:29Z 2017 Nanograin boundaries and silicon carbide photoluminescence / S.I. Vlaskina, G.N. Mishinova, V.I. Vlaskin, V.E. Rodionov, G.S. Svechnikov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 3. — С. 344-348. — Бібліогр.: 12 назв. — англ. 1560-8034 PACS: 64.70.K-, 77.84.Bw, 81.30.-t https://nasplib.isofts.kiev.ua/handle/123456789/214947 https://doi.org/10.15407/spqeo20.03.344 The luminescence spectra of SiC crystals and films with grain boundaries (GB) on the atomic level were observed. The GB spectra are associated with luminescence centers localized in areas of specific structural abnormalities in the crystal, without reference to the one-dimensional layer-disordering. The zero-phonon part of GB spectra is always within the same energy range (2.890…2.945 eV) and does not fit in the dependence of its position in the energy scale on the percent of hexagonality, as in the case of stacking faults (SFᵢ) and deep level (DLᵢ) spectra. The zero-phonon part 2.945…2.890 eV with a fine structure is better observed in crystals with the centers of origin growth of the crystal, if Nᴰ – Nᴬ ~ (2…8)·10¹⁶ cm⁻³, ND ~ (2…7)·10¹⁷ cm⁻³. The edge phonons of the Brillouin zone TA-46 meV, LA-77 meV, TO-95 meV, and LO-104 meV are involved in the development of the GB spectrum. This spectrum may occur simultaneously with the DLᵢ and SFᵢ ones. The GB spectra also occur after high-temperature processing of the β-phase (in the 3C-SiC) with the appearance of the α-phase. The temperature range of observation is 4.2…40 K. There is synchronous thermal quenching of all elements in the fine structure. The thermal activation energy of quenching is Еₐᵀ ~ 7 meV. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Nanograin boundaries and silicon carbide photoluminescence Article published earlier |
| spellingShingle | Nanograin boundaries and silicon carbide photoluminescence Vlaskina, S.I. Mishinova, G.N. Vlaskin, V.I. Rodionov, V.E. Svechnikov, G.S. |
| title | Nanograin boundaries and silicon carbide photoluminescence |
| title_full | Nanograin boundaries and silicon carbide photoluminescence |
| title_fullStr | Nanograin boundaries and silicon carbide photoluminescence |
| title_full_unstemmed | Nanograin boundaries and silicon carbide photoluminescence |
| title_short | Nanograin boundaries and silicon carbide photoluminescence |
| title_sort | nanograin boundaries and silicon carbide photoluminescence |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/214947 |
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