Defect reorganization induced by pulsed magnetic field in porous InP
We present results of investigations of the effect caused by weak magnetic field (B = 60 mT) in porous InP crystals of impurity-defect composition. This effect was found when studying the spectra of radiative recombination within the range 0.6 to 2.0 µm at 77 K. It was obtained that field influen...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2010
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| Цитувати: | Defect reorganization induced by pulsed magnetic field in porous InP / V.V. Milenin, R.A. Red’ko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 3. — С. 330-333. — Бібліогр.: 8 назв. — англ. |
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Milenin, V.V. Red’ko, R.A. 2017-05-30T06:56:12Z 2017-05-30T06:56:12Z 2010 Defect reorganization induced by pulsed magnetic field in porous InP / V.V. Milenin, R.A. Red’ko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 3. — С. 330-333. — Бібліогр.: 8 назв. — англ. 1560-8034 PACS 78.55.Mb https://nasplib.isofts.kiev.ua/handle/123456789/118402 We present results of investigations of the effect caused by weak magnetic field (B = 60 mT) in porous InP crystals of impurity-defect composition. This effect was found when studying the spectra of radiative recombination within the range 0.6 to 2.0 µm at 77 K. It was obtained that field influence initiates long-term changes in the intensity of radiative recombination inherent to centers of different nature. A possible mechanism of observed transformation is discussed. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Defect reorganization induced by pulsed magnetic field in porous InP Article published earlier |
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Defect reorganization induced by pulsed magnetic field in porous InP |
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Defect reorganization induced by pulsed magnetic field in porous InP Milenin, V.V. Red’ko, R.A. |
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Defect reorganization induced by pulsed magnetic field in porous InP |
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Defect reorganization induced by pulsed magnetic field in porous InP |
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Defect reorganization induced by pulsed magnetic field in porous InP |
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Defect reorganization induced by pulsed magnetic field in porous InP |
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defect reorganization induced by pulsed magnetic field in porous inp |
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Milenin, V.V. Red’ko, R.A. |
| author_facet |
Milenin, V.V. Red’ko, R.A. |
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2010 |
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English |
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Semiconductor Physics Quantum Electronics & Optoelectronics |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Article |
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We present results of investigations of the effect caused by weak magnetic
field (B = 60 mT) in porous InP crystals of impurity-defect composition. This effect was
found when studying the spectra of radiative recombination within the range 0.6 to
2.0 µm at 77 K. It was obtained that field influence initiates long-term changes in the
intensity of radiative recombination inherent to centers of different nature. A possible
mechanism of observed transformation is discussed.
|
| issn |
1560-8034 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/118402 |
| citation_txt |
Defect reorganization induced by pulsed magnetic field in porous InP / V.V. Milenin, R.A. Red’ko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 3. — С. 330-333. — Бібліогр.: 8 назв. — англ. |
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AT mileninvv defectreorganizationinducedbypulsedmagneticfieldinporousinp AT redkora defectreorganizationinducedbypulsedmagneticfieldinporousinp |
| first_indexed |
2025-11-24T16:25:17Z |
| last_indexed |
2025-11-24T16:25:17Z |
| _version_ |
1850482373872844800 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 3. P. 330-333.
PACS 78.55.Mb
Defect reorganization induced by pulsed magnetic field
in porous InP
V.V. Milenin, R.A. Red’ko
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine
41, prospect Nauky, 03028 Kyiv, Ukraine
Phone: 38 (044) 525-94-64, 525-61-82; e-mail: re_rom@ukr.net
Abstract. We present results of investigations of the effect caused by weak magnetic
field (B = 60 mT) in porous InP crystals of impurity-defect composition. This effect was
found when studying the spectra of radiative recombination within the range 0.6 to
2.0 µm at 77 K. It was obtained that field influence initiates long-term changes in the
intensity of radiative recombination inherent to centers of different nature. A possible
mechanism of observed transformation is discussed.
Keywords: photoluminescence, weak magnetic field, impurity-defect composition.
Manuscript received 08.04.10; accepted for publication 08.07.10; published online 30.09.10.
1. Introduction
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
15 cm−
cm5−
318 cm10 −×
Great attention to obtaining and researching self-
organized semiconductor layers of low dimensions based
on III-V single crystals arose in recent years. It is
possible to relate to their number porous materials
created by arrays of long channels with a submicrometer
cross-section that appear during anode etching of
semiconductor by halogenous electrolytes. Due to
qualitatively new properties that are absent in bulk
materials, the possibility to use single crystal substrate
with known parameters and simplicity of technology for
porous structure formation in the reason for wide interest
to these objects. Besides, in recent years porous layers
were applied in technology to obtain epitaxial layers
with good structural perfection. For example in [1], it
has been shown that use a porous substrate gives InP
epitaxial layers with a low number of elastic strains and
low concentration of dislocations. Therefore, search of
new technological methods to influence on the structure
of porous materials is now very topical. Pulsed magnetic
field (MF) treatment is the more perspective and cost-
effective one. Influence of this field on the electron spin
localized on defect in semiconductor results in changes
of mechanical and electro-physical properties [2].
At the same time, researching defect reorganization
caused by MF treatment of III-V semiconductors has not
been developed yet. There are no experimental results
indicative of interrelation processes between
microstructure of defects and efficiency of the reaction
conditioned by treatment in weak MF.
2
Thus, to ascertain the nature of MF phenomena in
semiconductor crystals, on the one hand, researches
carried out at MF treatment of defect structure using
spectroscopic methods and, on the other hand, the
objects with different structural states are required. In
this case, porous structures are more interesting due to
its formation occurring in irreversible, non-linear
processes and very non-equilibrium thermodynamic
conditions, but its microcrystalline structure has much
wider surface area, than that of bulk material.
2. Experimental
The defect structure of the samples was studied using the
photoluminescence (PL) method at 77 K in the spectral
range 0.5…2.0 eV. Excitation of PL was realized using
light of a powerful lamp with hν > 2.0 eV. The
absorption coefficient of investigated semiconductor in
this spectral range was ~10 . Thus, the spectrum
of defects was studied within the subsurface layers with
the depth close to ~10 . Porous structures prepared
in accord with the technique described in [1] on low-
resistivity n-type indium phosphide with the surface
orientation (100) and concentration of carriers close to
was the object of our investigations.
330
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 3. P. 330-333.
3. Results and discussion
Atomic force microscopy (AFM) images of por-InP
samples, which confirmed a different level of structural
homogeneity in the prepared objects, are shown in
Fig. 1.
After the cause of etching that lasted more than
25 s, the layers with a higher density of pores making a
regular network were obtained (Fig. 1a). The optical
measurements of reflectivity were carried out at 300 K
within the spectral range of 950 to 1100 nm and resulted
in interference image. The latter was formed by two
interfering optical beams: reflected from surface of the
porous layer and from porous layer-substrate interface.
This fact testifies about the high level of phase
homogeneity in the above layers.
To ascertain features of recombination processes in
porous structures and possibility of influence of the pore
surface, we consider changes in parameters of PL bands
with time after treatment in MF (B = 60 mT, f = 10 Hz,
t = 60 s) in more details (Fig. 2).
PL spectra of our samples in their initial state
consist of only two bands – at 1.15 and 0.9 eV. The
band-to-band radiative recombination at 1.41 eV (at
77 K) was not observed. Perhaps, due to absorption of
this emission in porous sublayer bulk and re-radiation
via the localized levels of pore surface [1]. If the density
of localized states is sufficiently large, it results in
narrowing of por-InP band gap and in red band shift.
The band in the region of 1.15 eV is caused by
complexes of native point defects. X-ray photoelectron
spectroscopy experimental data confirm it [1]. It was
obtained that the sample surface and bulk of the porous
layer are passivated by products of electrochemical
oxidation, i.e. in this case reduction of the surface state
density could be found.
On the other hand, electrochemical etching results
in infringement of stoichiometry of the initial crystal and
enrichment of near-surface layer by P vacancies. The
latter can form associative pairs with impurities and
other defects, which results in appearance of impurity
bands: with and wide with a lower
intensity at . According to [3], we should
believe that the second band is related with donor-
antisite defect P
eV15.11
max =νh
eV9.02
max =νh
In. But for large concentration of PIn,
deviation of the InP sample stoichiometry toward an
excess of metalloid is required, which is in contradiction
with the results of electrochemical etching. However, if
we consider a presence in the composition of the In
oxide passivated layer, then appearance of the antisite
defect like PIn in small concentrations can be found
probably. The latter results in appearance of the band
with low intensity related with this defect. This is in
good agreement with our experimental data.
The MF treatment resulted in essential increase in
the intensity of the band at 1.15 eV. The intensity of the
second band increases, too, but much less than the latter
one. The frequency positions of PL peaks do not vary.
The intensity of the band with
decreases down to the initial value after some time
interval (several days), but for the second peak it does
not vary. Much longer time delay (up to 7 days) results
in increase of the intensity of both bands.
eV15.11
max =νh
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
Fig. 1. Different microrelief of porous material.
Thus, the phenomena of short-term effect of MF
treatment on porous InP structures resulted in long-term
non-monotonous changes in its PL intensity was found.
One can ask about a reason of observable changes.
Popular believe held that the intensity of PL increases,
while the concentration of non-radiative centers
decreases, and vice versa. Absence of the edge band is
indicative of a high concentration of these defects. But
the questions about non-monotonous, long-term changes
in the PL intensity of observable bands and role of MF
in these phenomena are still open.
According to [4], MF treatment of SiO2-Si
structures results in relaxation of internal mechanical
strains, which possesses non-monotonic view. It should
be noted that the strains of squeezing of near-surface
layer were transformed to strains of tension but then
returned to initial ones. The relaxation process starts at
treatment and proceeds during several days. It is
accompanied by changes in the thickness of oxide layer:
at first, it decreases, but then it becomes larger.
There is a high concentration of strain and broken
bonds in near-surface layers of spatially-
nonhomogeneous porous structures. So, we consider that
the above phenomena take place in our case, too. The
most probable mechanism of MF influencing on
331
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 3. P. 330-333.
semiconductor material is as follows. Strained chemical
bonds are weakened due to magnetic-induced
intercombination transitions of electrons that take part in
formation of these bonds. On the other hand, the
polarization of nucleus magnetic isotopes (31P, spin
2
1
=I ), when electrons change their spin orientation due
to nuclear relaxation and pass to antibonding states [5],
can results in this weakening. The destruction of
weakened chemical bonds due to thermal fluctuation and
mechanical strains is accompanied by appearance of
mobile charged point defects and amplification of
oxidation processes. It should be noted that the peak of
pulsed MF effect (increase in the oxide layer thickness)
was reached in 5 to 6 days after treatment [6]. Oxidation
of the surface results in its passivation (decrease of
surface electron levels density), i.e. in the decrease of
radiationless recombination. The increase in PL intensity
after 8-days delay in our case can appear due to such
process.
It should be emphasized that the presence of
native mechanical strains and their relaxation can result
in reorganization of defects in semiconductor, too. In
the work [7], authors have observationally proved the
necessity of the account of deformation effects when
observing reorganization of local centers in GaAs
interface. According to [8], the presence of elastic
strains causes the change in the chemical potential of
point defects as compared with that of non-deformed
crystals. The direct diffusion flux of these defects
appears due to this circumstance. The state of
vacancies supersaturation is realized at the strains of
squeezing presence. This supersaturation relaxes to
new equilibrium state of the system due to the flow of
vacancies and dislocations to surface region, or/and to
creation of complexes and clusters of point defects. If
the strains of tension are present, we deal with
destruction of these complexes and clusters that consist
of vacancies. The level of supersaturation or
undersaturation by vacancies depends on the
concentration of doped and background impurities,
which can take part in formation of the impurity-
vacancy complexes – the centers of radiative and
nonradiative recombination. The observed features of
reorganization in the impurity-defect structure in
conditions of changing the strain “sign” of
semiconductor state after MF treatment [4] can result in
the change of spectral allocation of radiation. I.e., it can
result in the increase or decrease in the PL intensity of
impurity bands, as it was obtained in [7] where
correlation of the strain “sign” in the semiconductor
structures with the changes in PL spectra was obtained.
Processes of the association of defects in
complexes and the dissociation of the lasts at room
temperature are slowed due to a low value of the
diffusion factors of native and impurity defects. It can be
the reason of the observed long-term changes in PL
spectra.
0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4
0,0
0,2
0,4
0,6
0,8
1,0
P
L
in
te
ns
ity
, a
rb
. u
ni
ts
Photon energy, eV
initial state
as-treated in MF
1 day
7 days
Fig. 2. PL spectra of porous InP of the first group (Fig. 1a).
0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5
0,0
0,2
0,4
0,6
0,8
1,0
PL
in
te
ns
ity
, a
rb
. u
ni
ts
Photon energy, eV
initial state
as-treated in MF
1 day
7 day
8 day
Fig. 3. PL spectra of porous InP of the second group (Fig. 1b).
The spectral dependences of the reflectivity in the
structures with morphology shown in Fig. 1 were similar
to those of bulk material. However, the value of
reflectivity for porous layer was smaller than that for
bulk semiconductor. The latter is caused, perhaps, by the
increase of the contribution of diffusion dissipation in
these objects. As to these samples, the differences in PL
spectra were obtained (Fig. 3).
The weak edge emission at in
these samples, at difference from previous structures,
has been observed. A big half-width of this band testifies
about its not-simplicity. Probably, it has been created by
bands with different but close maximums. The wide
impurity bands testify about large chemical and spatial
non-regularities of centers corresponding to observed
emission. The treatment in MF results in quenching all
the observed impurity bands, but edge and new at
ones appear. The latter is related,
perhaps, with radiative recombination caused by
continuum of surface levels, situated below the
conduction band that resulted in red shift of edge peak.
Long-term changes in PL spectra similar to those in the
first group were obtained.
eV41.1edge
max =νh
eV3.13
max =νh
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
4. Conclusion
332
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 3. P. 330-333.
The results of our structural, photoluminescence and
optical investigations of the nanostructured InP have
demonstrated a qualitative similarity of reorganization of
defect structure for both groups of semiconductor caused
by MF that are in good agreement with noted
conception. Some differences in spectra of radiative
recombination can be explained by deviation in
impurity-defect composition of initial substrate,
morphology of porous layers, value of internal
mechanical strains and oxide processes.
This research was supported by a Grant ДЗ/478-
2009 from the Ministry of Education and Science of
Ukraine.
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