Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films
The electroreflectance method based on the electrolyte technique is used for investigation of electron transitions E₀, E₀ + Δ₀ in homoepitaxial films n-GaP (111) with the electron concentration 5.7*10²³ m⁻³ before and after irradiation by ⁶⁰Co gamma quanta in the dose range 10⁵ – 10⁶ rad under the r...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2004
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| Zitieren: | Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films / P.A. Gentsar, A.A. Kudryavtsev // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2004. — Т. 7, № 3. — С. 240-242. — Бібліогр.: 7 назв. — англ. |
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irk-123456789-1191172017-06-05T03:02:32Z Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films Gentsar, P.A. Kudryavtsev, A.A. The electroreflectance method based on the electrolyte technique is used for investigation of electron transitions E₀, E₀ + Δ₀ in homoepitaxial films n-GaP (111) with the electron concentration 5.7*10²³ m⁻³ before and after irradiation by ⁶⁰Co gamma quanta in the dose range 10⁵ – 10⁶ rad under the room temperature. The authors observed splitting the low-energy extremum after irradiation. The decrease in internal mechanical strains inside the films as a result of gamma irradiation was estimated via changes of the electron transition energy and collision parameter of widening. Also estimated is the time of charge carrier energy relaxation after irradiation. 2004 Article Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films / P.A. Gentsar, A.A. Kudryavtsev // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2004. — Т. 7, № 3. — С. 240-242. — Бібліогр.: 7 назв. — англ. 1560-8034 PACS: 73.20; 78.66 http://dspace.nbuv.gov.ua/handle/123456789/119117 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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The electroreflectance method based on the electrolyte technique is used for investigation of electron transitions E₀, E₀ + Δ₀ in homoepitaxial films n-GaP (111) with the electron concentration 5.7*10²³ m⁻³ before and after irradiation by ⁶⁰Co gamma quanta in the dose range 10⁵ – 10⁶ rad under the room temperature. The authors observed splitting the low-energy extremum after irradiation. The decrease in internal mechanical strains inside the films as a result of gamma irradiation was estimated via changes of the electron transition energy and collision parameter of widening. Also estimated is the time of charge carrier energy relaxation after irradiation. |
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Article |
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Gentsar, P.A. Kudryavtsev, A.A. |
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Gentsar, P.A. Kudryavtsev, A.A. Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Gentsar, P.A. Kudryavtsev, A.A. |
| author_sort |
Gentsar, P.A. |
| title |
Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films |
| title_short |
Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films |
| title_full |
Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films |
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Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films |
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Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films |
| title_sort |
radiation-stimulated relaxation of internal mechanical straines in homoepitaxial gap films |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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2004 |
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http://dspace.nbuv.gov.ua/handle/123456789/119117 |
| citation_txt |
Radiation-stimulated relaxation of internal mechanical straines in homoepitaxial GaP films / P.A. Gentsar, A.A. Kudryavtsev // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2004. — Т. 7, № 3. — С. 240-242. — Бібліогр.: 7 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
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AT gentsarpa radiationstimulatedrelaxationofinternalmechanicalstrainesinhomoepitaxialgapfilms AT kudryavtsevaa radiationstimulatedrelaxationofinternalmechanicalstrainesinhomoepitaxialgapfilms |
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2025-07-08T15:15:07Z |
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2025-07-08T15:15:07Z |
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1837092263095697408 |
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Semiconductor Physics, Quantum Electronics & Optoelectronics. 2004. V. 7, N 3. P. 240-242.
© 2004, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine240
PACS: 73.20; 78.66
Radiation-stimulated relaxation
of internal mechanical straines
in homoepitaxial GaP films
P.A. Gentsar, A.A. Kudryavtsev
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 45, prospect Nauki, 03028 Kyiv, Ukraine
E-mail: journal@isp.kiev.ua
Abstract. The electroreflectance method based on the electrolyte technique is used for investi-
gation of electron transitions E0, E0 + ∆0 in homoepitaxial films n-GaP (111) with the electron
concentration 5.7⋅1023 m�3 before and after irradiation by 60Co gamma quanta in the dose
range 105 � 106 rad under the room temperature. The authors observed splitting the low-energy
extremum after irradiation. The decrease in internal mechanical strains inside the films as a
result of gamma irradiation was estimated via changes of the electron transition energy and
collision parameter of widening. Also estimated is the time of charge carrier energy relaxation
after irradiation.
Keywords: electroreflectance, gallium phosphide, homoepitaxial film.
Paper received 23.03.04; accepted for publication 21.10.04.
Heteroepitaxial deposition of semiconductor films is
widely used in currently electronics and physical investi-
gations. And the characteristic feature of heterosystems
obtained in this way is the presence of internal mechani-
cal straines in them.
These straines arising due to some mismatch between
lattice constants of the film and substrate as well as dif-
ferences of their thermal expansion coefficients result in
various effects: from changes of the energy band struc-
ture up to appearance of technological defects at inter-
faces [1].
Their changes in the course of semiconductor device
exploitation reduce the operation stability of these de-
vices [2]. However, internal mechanical straines can also
arise in homoepitaxial systems being caused by a differ-
ence in the charge carrier concentrations inherent to the
film and substrate [3].
The modulation electroreflectance spectroscopy plays
an important role in investigations of the band structure
in solids, which stems from its high resolution ability. In
comparison with the classical spectroscopy, the electro-
reflectance one is more sensitive to changes in the semi-
conductor energy spectrum [4,5]. In this report, the
electroreflectance method is used to study the impact of
gamma irradiation on internal straines in homoepitaxial
gallium phosphide films.
We studied electroreflectance spectra of homoepi-
taxial n-GaP (111) films with the electron concentration
5.7⋅1023 m�3 before and after irradiation with 60Co gamma
quanta within the dose range 105 � 106 rad. The films of
the thickness 10�7...5·10�6 m were prepared using the gas-
phase epitaxy on n-GaP substrates with the electron con-
centration 1024 m�3.
The electroreflectance signal was measured under the
room temperature using the electrolyte technique (elec-
trolyte was water solution of 1N KCl) and the first modu-
lation harmonic frequency 2.2 kHz with the threshold
sensitivity 5·10�6 and spectral resolution 0.003 eV.
The measurements were performed within the spec-
tral range 2.5�3.2 eV including the direct transitions
Å0(Ã8V � Ã6Ñ) and Å0 + ∆0(Ã7V � Ã6Ñ) in non-polarized
light, since the polarization dependence of electro-
reflectance is absent in the case of (111) surface.
Shown in Fig. 1 are electroreflectance spectra of films
before (curve 1) and after (curve 2) irradiation with
gamma quanta by using the dose 2·105 rad. To avoid the
effect of field widening, our spectral measurements were
performed applying the same electric fields to the sam-
ples (the constant bias was equal to �0.6 V).
The spectrum of non-irradiated film (curve 1) consists
of two peaks: negative and positive ones. A high level of
mechanical straines at the heterointerface and inside the
film resulted in tailing the spectrum.
The electron transitions E0 with the energy 2.74 eV
and E0 + ∆0 with the energy 2.84 eV of GaP [6] remain
unresolved here. In this case, the forbidden gap width E0
P.A. Gentsar, A.A. Kudryavtsev: Radiation-stimulated relaxation of internal ...
241SQO, 7(3), 2004
was determined using the value of the first extremum in
the spectrum, while the collision parameter of widening
à was determined via the halfwidth of this peak. The ob-
tained E0 and Γ values for the non-irradiated sample were
2.772 and 0.146 eV, respectively.
After irradiation of the film with the dose 2⋅105 rad
(curve 2), mechanical straines were reduced, the system
approached to its structurally equilibrium state. There
were observed an increase in peak amplitudes and nar-
rowing the spectral band.
It should be noted that the curve 1 was obtained under
the modulation voltage 0.9 V and the curve 2 under 0.5 V.
As known, under increasing modulation voltage, the peak
amplitude should increase [4]. In our experiments, we
observed the higher signal amplitude for the lower modu-
lation voltage (curve 2).
When the electric field in the depletion layer of the
irradiated film is increased (constant bias is equal to
�0.2 V), the peak amplitude rises more and more (Fig. 2).
Besides, the energy positions of peaks in the electro-
reflectance spectrum and separation between them are
changed, too. After irradiation of the films, E0 peak shifted
by the value ∆E0 = 0.043 eV into the lower energy side
(Fig. 1, curve 2).
It implies that the initial homoepitaxial system pos-
sessed internal mechanical straines of the compression
type.
Under the hydrostatic pressure P, the change in the
transition energy is
V
VDD
E VC ∆−
=∆
)(
0 , where DC and
DV are deformation potentials of the conduction and va-
lence band, respectively [7]; ∆V/V = �3P(S11 + 2S12) is
the relative volume change, where (S11+2S12)�1 =
C11+2C12.
Then,
)2(
)(3
/
1211
0
CC
DD
PE VC
+
−−
=∆ . For GaP: (DC � DV) =
= �9.3 eV; C11 = 1.412·1011 Pa; C12 = 0.625·1011 Pa, where
C11 and C12 are elastic moduli [5]. Thereof, one can get
the value of the coefficient of GaP transition energy
change caused by the applied hydrostatic pressure
∆E0/∆P = 1.05·10�10 eV/Pa.
The estimation of the change in the value of internal
mechanical straines in GaP film when ∆E0 = 0.043 eV
gives the value ∆Ð = 4.1·108 Pa.
In the case of uniaxial compression in [111] direc-
tion,
44
44
0 1
3
1
3
1
C
ddS
P
E
==
∆
, where d is the shear
deformation potential; C44 � elastic modulus (d = �4.5 eV,
C44 = 0.705·1011 Pa for GaP) [5]. Then, ∆E0/∆P =
= 0.369·10�10 eV/Pa, and the change of internal mechani-
cal straines with ∆E0 = 0.043 eV is 11.7·108 Pa as a re-
sult of gamma irradiation.
Consequently, under gamma ray action with the dose
value 2⋅105 rad, the mechanical straines in GaP film were
decreased by the value averaged between the values
4.1⋅108 Pa (hydrostatic pressure) and 11.7⋅108 Pa
(uniaxial compression in [111] direction), that is by
7.9·108 Pa (biaxial compression).
When applying the constant bias �0.2 V to irradiated
samples, except the increase of the amplitude in spectra,
we can observe more clear spectral resolution of E0 and
E0 + ∆0 transitions.
It is clearly seen from Fig. 2 that the low-energy
extremum is splitted due to the reduced scattering of
charge carriers, and owing to the fact the amplitude of
the electroreflectance signal increases as caused by tran-
sitions from the spin-orbitally off-splitted valence band.
The difference between energies of the main and off-
splitted peaks in Fig. 2 corresponds to the value of the
spin-orbital splitting ∆0 = Γ8v � Γ7v = 0.11 eV, which is in
good agreement with the value 0.10 eV given in [6].
The decrease of the collision parameter of widening Γ
after irradiation from 0.146 down to 0.080 eV is indica-
tive of the increasing time of charge carrier energy re-
laxation τ = h /Γ from 4.5·10�15 up to 8.2·10�15 s and the
tendency of the initial homoepitaxial system with me-
chanical straines to approach to its structurally equilib-
rium state.
With increasing the irradiation dose up to 106 rad,
the transition energies were practically not changed,
while the widening parameter was slightly decreased.
Thus, the analysis of the obtained electroreflectance
spectra of n-GaP homoepitaxial films has shown that the
films grown by using gas-phase epitaxy possess rather
high internal mechanical compression straines.
Under 2⋅105 rad gamma irradiation action, these were
decreased by the value 7.9⋅108 Ðà as a result of radia-
D ´R R/ 104
1
0
�1
�2
2.5
2
1
2.9 3.1 E, eV
Fig. 1. Electroreflectance spectra of n-GaP (111) film before (1)
and after (2) irradiation by γ-guanta with the dose 2⋅105 rad. The
constant bias is � 0.6 V. The modulating voltages are: 1 � 0.9; 2 �
0.5 V. The flat-band potential is equal to 2.1 V.
242
SQO, 7(3), 2004
P.A. Gentsar, A.A. Kudryavtsev: Radiation-stimulated relaxation of internal ...
tion-stimulated relaxation of internal mechanical strai-
nes. As a consequence, reduced was the scattering of light-
excited charge carriers, and the time of there energy re-
laxation increased from 4.5⋅10�15 up to 8.2⋅10�15 s.
Unresolved E0 and E0 + ∆0 electron transitions in ini-
tial homoepitaxial GaP films characterized by blurred
electroreflectance bands, which is caused by internal
mechanical straines in them, were resolved only after
radiation-stimulated relaxation of these straines.
The determined value of the spin-orbital splitting ∆0 =
= Γ8v � Γ7v = 0.11 eV coincides with the literature data.
The obtained results can be used when elaborating a ra-
diation technology for manufacturing new generation
devices based on GaP homoepitaxial films.
References
1. E.F. Venger, L.A. Matveeva // Neorganicheskiye materialy,
33(2), p. 153-157 (1997), in Russian.
2. Yu. A. Tkhorik, Structural relaxation in semiconductor crys-
tals and device structures. �Naukova dumka�, Kyiv,1994,
247 p. (in Russian).
3. O.Yu. Borkovskaya, S.A. Grusha, N.L. Dmitruk et al. //
Zhurnal tekhnicheskoi fiziki, 55(10), p. 1977-1982 (1985), in
Russian.
4. V.A. Tyagai, O.V. Snitko, Light electroreflectance in semicon-
ductors. �Naukova dumka�, Kyiv, 1980, 302 p. (in Russian).
5. P. Yu, M. Cardona. Principles of semiconductor physics.
�Fizmatlit�, Moscow, 2002, 560 p. (in Russian).
6. M. Cardona, K.L. Shaklee, F.H. Pollak // Phys. Rev., 154(3),
p. 696-720 (1967).
7. G.L. Bir, G.E. Pikus. Symmetry and deformational effects in
semiconductors. �Nauka�, Moscow, 1972, 584 p. (in Rus-
sian).
DR R/ ´104
0
�1
�2
2.5
1
2.9 3.1 E, eV
Fig. 2. Electroreflectance spectrum of n-GaP film after irradia-
tion by γ-guanta with the dose 2⋅105 rad. The constant bias is �
0.2 V, modulating voltages is 0.5 V.
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