Parameters of the energy spectrum for holes in CuInSe₂
This paper reports the coefficients Ca,b for the k-linear term in dispersion relation E(k) for holes of the upper valence bands Г⁻₆ and Г⁺₇ in p-CuInSe₂ crystals. We also obtained the tensor components for the carrier effective masses, in all three valence sub-bands of the model semiconductor. I...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2009
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Цитувати: | Parameters of the energy spectrum for holes in CuInSe₂ / P.М. Gorley, I.V. Prokopenko, О.О. Galochkinа, P.P. Horley, Yu.V. Vorobiev, J. Gonzalez-Hernandez // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2009. — Т. 12, № 3. — С. 302-308. — Бібліогр.: 30 назв. — англ. |
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irk-123456789-1188812017-06-01T03:06:14Z Parameters of the energy spectrum for holes in CuInSe₂ Gorley, P.М. Prokopenko, I.V. Galochkinа, О.О. Horley, P.P. Vorobiev, Yu.V. González-Hernández, J. This paper reports the coefficients Ca,b for the k-linear term in dispersion relation E(k) for holes of the upper valence bands Г⁻₆ and Г⁺₇ in p-CuInSe₂ crystals. We also obtained the tensor components for the carrier effective masses, in all three valence sub-bands of the model semiconductor. It was shown that the energy spectrum parameters for holes in CuInSe₂ allow successful explanation for the anisotropy of tensor components describing the interband light absorption coefficient and the published data for the temperature variation of the Hall coefficient, total Hall mobility and thermal voltage within the temperature range 100 K ≤ T ≤ 350 K. 2009 Article Parameters of the energy spectrum for holes in CuInSe₂ / P.М. Gorley, I.V. Prokopenko, О.О. Galochkinа, P.P. Horley, Yu.V. Vorobiev, J. Gonzalez-Hernandez // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2009. — Т. 12, № 3. — С. 302-308. — Бібліогр.: 30 назв. — англ. 1560-8034 PACS 61.50.Ah 71.20.-b, 73.50.Lw http://dspace.nbuv.gov.ua/handle/123456789/118881 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
description |
This paper reports the coefficients Ca,b for the k-linear term in dispersion
relation E(k) for holes of the upper valence bands Г⁻₆ and Г⁺₇ in p-CuInSe₂ crystals. We
also obtained the tensor components for the carrier effective masses, in all three valence sub-bands of the model semiconductor. It was shown that the energy spectrum parameters for holes in CuInSe₂ allow successful explanation for the anisotropy of tensor
components describing the interband light absorption coefficient and the published data
for the temperature variation of the Hall coefficient, total Hall mobility and thermal
voltage within the temperature range 100 K ≤ T ≤ 350 K. |
format |
Article |
author |
Gorley, P.М. Prokopenko, I.V. Galochkinа, О.О. Horley, P.P. Vorobiev, Yu.V. González-Hernández, J. |
spellingShingle |
Gorley, P.М. Prokopenko, I.V. Galochkinа, О.О. Horley, P.P. Vorobiev, Yu.V. González-Hernández, J. Parameters of the energy spectrum for holes in CuInSe₂ Semiconductor Physics Quantum Electronics & Optoelectronics |
author_facet |
Gorley, P.М. Prokopenko, I.V. Galochkinа, О.О. Horley, P.P. Vorobiev, Yu.V. González-Hernández, J. |
author_sort |
Gorley, P.М. |
title |
Parameters of the energy spectrum for holes in CuInSe₂ |
title_short |
Parameters of the energy spectrum for holes in CuInSe₂ |
title_full |
Parameters of the energy spectrum for holes in CuInSe₂ |
title_fullStr |
Parameters of the energy spectrum for holes in CuInSe₂ |
title_full_unstemmed |
Parameters of the energy spectrum for holes in CuInSe₂ |
title_sort |
parameters of the energy spectrum for holes in cuinse₂ |
publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
publishDate |
2009 |
url |
http://dspace.nbuv.gov.ua/handle/123456789/118881 |
citation_txt |
Parameters of the energy spectrum for holes in CuInSe₂ / P.М. Gorley, I.V. Prokopenko, О.О. Galochkinа, P.P. Horley, Yu.V. Vorobiev, J. Gonzalez-Hernandez // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2009. — Т. 12, № 3. — С. 302-308. — Бібліогр.: 30 назв. — англ. |
series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
work_keys_str_mv |
AT gorleypm parametersoftheenergyspectrumforholesincuinse2 AT prokopenkoiv parametersoftheenergyspectrumforholesincuinse2 AT galochkinaoo parametersoftheenergyspectrumforholesincuinse2 AT horleypp parametersoftheenergyspectrumforholesincuinse2 AT vorobievyuv parametersoftheenergyspectrumforholesincuinse2 AT gonzalezhernandezj parametersoftheenergyspectrumforholesincuinse2 |
first_indexed |
2025-07-08T14:49:48Z |
last_indexed |
2025-07-08T14:49:48Z |
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1837090670912733184 |
fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 3. P. 302-308.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
302
PACS 61.50.Ah 71.20.-b, 73.50.Lw
Parameters of the energy spectrum for holes in CuInSe2
P.М. Gorley1, I.V. Prokopenko2, О.О. Galochkinа1, P.P. Horley1,3, Yu.V. Vorobiev4, J. González-Hernández5
1Yu. Fedkovych Chernivtsi National University, 2, Kotsyubynsky str., 58012 Chernivtsi, Ukraine,
phone: +38 (03722) 46-877, e-mail: semicon-dpt@chnu.edu.ua
2V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41, prospect Nauky, 03028 Kyiv, Ukraine
3Centro de Física das Interacções Fundamentais (CFIF), Instituto Superior Técnico,
Avenida Rovisco Pais, 1049-001 Lisboa, Portugal
4CINVESTAV-IPN Unidad Querétaro, Libramiento Norponiente 2000, Fracc. Real Juriquilla,
76230 Querétaro, México
5CIMAV, Miguel de Cervantes 120, Complejo Industrial Chihuahua, 31109 Chihuahua, México
Abstract. This paper reports the coefficients BAC , for the k-linear term in dispersion
relation E(k) for holes of the upper valence bands 6 and 7 in p-CuInSe2 crystals. We
also obtained the tensor components for the carrier effective masses CBAm ,,
||, in all three
valence sub-bands of the model semiconductor. It was shown that the energy spectrum
parameters for holes in CuInSe2 allow successful explanation for the anisotropy of tensor
components describing the interband light absorption coefficient and the published data
for the temperature variation of the Hall coefficient, total Hall mobility and thermal
voltage within the temperature range 100 K ≤ T ≤ 350 K.
Keywords: chalcopyrite structure, СuInSe2, non-parabolic dispersion relation,
components of the effective mass tensor, kinetic coefficient, light absorption coefficient.
Manuscript received 28.04.09; accepted for publication 00.00.09; published online 00.00.09.
1. Introduction
Direct-band chalcopyrite compound СuInSe2 belongs to
AIBIICVI
2 semiconductors that are considered as analogs
to AIIBVI binary systems. Due to their high absorption
coefficient [1] (about (3…6)∙107m–1) these materials are
very promising for the efficient photovoltaic device
applications [2]. In general, СuInSe2 crystals are studied
in deeper detail comparing with the other AIBIICVI
2
compounds (e.g., [3-5]). However, the exact nature of
some of their properties is not clearly revealed yet. In
particular, it concerns the fundamental parameters
characterizing the valence band structure. According to
the results of the theoretical calculations [6, 7], the band
structure of the bulk AIBIICVI
2 semiconductors in the
center of the Brillouin zone obeys anisotropic non-
parabolic dispersion relation E(k) including a k-linear
term. To the best of the authors’ knowledge, the
numerical values of the coefficients С describing the
aforementioned term are not determined yet for p-
CuInSe2 crystals, while they are known for the AIIBVI
materials p-CdS, p-CdSe and p-ZnO. Moreover, only
three out of six components of the hole effective masses
for p-CuInSe2 were determined so far from the optical
studies [8]: those for spin-split band holes
(msh /m0 ≈ 0.085), heavy (mhh /m0 ≈ 0.71) and light holes
(mhl /m0 ≈ 0.092).
Our previous research [9] considered non-
parabolicity of the dispersion relation E(k) for the holes
in chalcopyrite-structure crystals under non-degenerate
statistics of the electron gas, deriving the analytical
expressions allowing to calculate the temperature and
concentration dependences of tensor components for the
thermal voltage, Hall coefficient and carrier mobility.
Carrier scattering by crystalline lattice defects was
considered in the approximation of time relaxation. For
the upper valence sub-bands 6 and 7 of p-CuInSe2,
we estimated the coefficients 76 ,
С characterizing the
contribution of k-linear term into E(k). The results of
further calculations agreed well with the experimental
temperature dependences of the Hall coefficient and
total Hall carrier mobility.
To improve the approach used in [9], we suggest
also to account for the symmetry relations binding the
tensor components of the inverse effective masses for
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 3. P. 302-308.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
303
the holes 1
,,
)(
776
m in chalcopyrite (wurtzite)
crystals [10-12]. This methodological improvement
would change the values of 76 ,
С obtained in [9],
leading to more exact results concerning the influence of
k-linear term of E(k) on the values and temperature
behavior of the kinetic coefficients in p-CuInSe2.
Moreover, proper accounting of the symmetry for the
components 1
,,
)(
776
m allows to get an accurate
magnitude estimation for all the inverse effective mass
components describing the holes in three valence sub-
bands of the material studied. Fitting the theoretical
calculations to the experimental data on temperature
dependences for the Hall coefficient, Hall mobility and
thermal voltage in p-CuInSe2 crystals allowed to
improve precision in determining 76 ,
С coefficients.
We have also shown that non-parabolicity contribution
to E(k) in the total Hall mobility decreased from about
50 % (T = 100 K) to 17 % (T = 300 K), enhancing the
previously reported data of ≈20 % and ≈10 %,
respectively [9].
2. Theory
Schematic depiction of the valence band diagram [4, 13]
for p-CuInSe2 around the center of the Brillouin zone is
shown in Fig. 1.
The dispersion relation for the carriers populating
the valence bands 6 , 7 and 7 (taking into account
spin-orbital interaction) can be written in the following
form [7]:
,
2
)/(
2
)(
,
||
2
||
2
22
,
,
,
2
,
0, 76
BABA
BA
BA
BA
m
k
Cmk
m
EkE
(1)
Fig. 1. Band diagram for р-CuInSe2; the designations are
explained in the text.
)(
2
)(
||
2
||
22
07 СС
С
m
k
m
k
EkE
, (2)
with transversal k = (kx
2+ky
2)1/2 and longitudinal k|| = kz
components of the wave vector k for CBAm ,,
and CBAm ,,
||
effective mass tensors describing the holes in the sub-
bands 6 (index А), 7 (index В) and 7 (index С)
regarding the high-symmetry axis of the crystal. The
coefficients BAC , characterize the deviation from
parabolicity in the dispersion relation E(k) for the
corresponding valence sub-bands. CBAE ,,
0 in (1) and (2)
describe the position of their extrema.
As the dispersion relation (1) is characteristic for
the semiconductors with chalcopyrite or wurtzite
structure of [14-17], it is natural to assume that the
components of the effective mass tensors for p-CuInSe2
would also satisfy the relations obtained for wurtzite
crystals [11, 12]:
ACBACB m
m
m
m
m
m
m
m
,
||
,
||
,
32
1
|| 1
)2)((
CC
rg
m
m
m
m
AA
,
ACAB m
m
m
m
C
m
m
m
m
||,||,
1
||,||,
,
AACC m
m
m
m
C
m
m
m
m
||
2
||
,
AABB m
m
m
m
C
m
m
m
m
||
3
||
. (3)
Here g, r, s, t denote m2/2 -normalized (ħ is
Planck’s constant and m is the free electron mass) matrix
elements for the interband interaction operators [12],
with adjustment parameters
gs
rt
,
rg
ts
1 , 11
2
2 1 CqС ,
)1()1( 11
2
3 CqC . (4)
The coefficient
)1/( 22
1 qqС
(5)
with
9/8
1
2
1
2
2
x
x
q (6)
depends on the energy split 3/1/ socrx caused
by the crystalline field cr and spin-orbital interaction
so [10]. It is important that the mc-normalized (m is
the electron mass and c is the speed of light) matrix
elements for the optical transitions from В/С valence
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 3. P. 302-308.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
304
sub-bands to the conduction band [10] also depends
on q2
2
|| 2 qMM CB , 2
|| 12 qMM BC , (7)
while for the A-band 0|| AM , 5.0
AM .
The experimental values eV006.0cr and
eV233.0 so [18] lead to C1 ≈ 1.9 > 1, proving that
for p-CuInSe2 (and also CdSe, ZnSe) the components of
the effective mass tensor for holes in the valence sub-
bands would satisfy the condition [12]:
Bm|| < Сm|| < Am|| , Am < Сm < Bm . (8)
It is important that for С1 < 1 (which is valid for
CdS, ZnS, ZnO and GaN), the components of symmetry
for the effective mass tensor are [10-12]
Сm|| < Bm|| < Am|| , Am < Bm < Сm . (9)
Comparison of (8) and (9) shows that changing
C1 > 1 for С1 < 1 will result in swapping of the valence
sub-bands В and С.
Formulas (5) and (7) yield a proportion
CB MMC ||||1 / BC MM / saying that the coefficient
C1 depends on the ratio of matrix elements for the
optical transitions (with the same polarization) from the
bands В/С into conduction band. Therefore, one can
assume that C1 should contribute somehow to the
anisotropy of the light absorption coefficient /||
(with parallel and perpendicular subscripts denoting light
polarization regarding the main optical axis of the
crystal).
3. Results and discussion
Using the symmetry relations (3) one can show that for
the present experimental effective mass values
describing the holes of p-CuInSe2 [8] the inequalities (8)
would be valid for these two particular cases (within
parameters with the precision of experimental
measurements):
Case D1: ,091.0
||
m
mA
,074.0
||
m
mB
,081.0||
m
mС
,087.0
m
mA
,73.0
m
mB
;162.0
m
mС
(10)
Case D2: ,71.0||
m
m A
,165.0||
m
mB
,260.0||
m
mС
,078.0
m
mA
,092.0
m
mB
.085.0
m
mС
(11)
Table 1 presents the anisotropy coefficients for
effective masses of holes
CBA
CBA
CBA
m
m
m
K
,,
,,
||,,
||,
. We
calculated the data both for p-CuInSe2 crystals and their
AIIBVI analogs using the experimental mass values for
CdSe, CdS [10] and ZnO [14].
Table 1. Anisotropy coefficients for hole effective masses in
p-СuInSe2 and AIIBVI analogs.
Material A
mK B
mK C
mK Eg, eV С1
Case C1 1.05 0.10 0.50
p-CIS Case C2 9.10 1.79 3.06 1.010[22] 1.90
p-CdSe 2.66 0.53 0.91 1.756[23] 1.65
p-CdS 4.70 0.76 0.48 2.485[23] 0.73
p-ZnO 5.07 3.76 0.24 3.370[23] 0.035
As one can see, for the case C1 (10) with increasing
band gap Eg (parameter С1 decreases) the anisotropy
coefficient for effective masses of the holes populating
А and В valence bands also increases. At the same time,
the coefficient for the С-band decreases for all the
studied materials except for CdSe. Effective mass
components calculated for the case D2 (11) for CuInSe2
violate this regularity for А and В-bands, to the contrary
restoring it for the С-band.
To define which of the cases D1 or D2 is correct for
р-CuInSe2, we used analytical expressions from [9] to
calculate temperature behavior of the tensors describing
the specific conductivity, Hall mobility and thermal
voltage. To define the fixed CBAm ,,
||, , the coefficients
BAC , in the dispersion relation (1) were considered as
parameters and adjusted to achieve the best fitting of the
calculated data to the experimental temperature curves
for the kinetic coefficients. The numerical values of
BAC , for р-CuInSe2 and AIIBVI are given in Table 2.
It is noteworthy that for all the studied compounds
we achieved an essentially linear dependence
)15.4(1065.4 2
gB EC eV·Å (Fig. 2, line 2),
allowing to assume the linearity of )( gA EC as well.
To obtain the latter (Fig. 2, line 1) the values of AC for
CdSe and CdS should be used in the place of those from
[15], which will allow to get the refined coefficients
(Table 2). Validity of )( 0,, gBABA EEkC
dependence for various wurtzite and chalcopyrite
crystals makes it possible to estimate the limit values of
BAC , coefficients for the case 0gE , yielding
263.0max AC eV·Å and 193.0max BC eV·Å,
respectively. On the other hand, for semiconductor with
the considered crystalline structure and a bandgap of
eV15.4gE , the contribution of k-linear term into
E(k) should be negligibly small. Due to this fact, for
example, the bandgap of BeO is not determined yet
exactly, so that the publication [19] usually mentions the
data in a wide range of 7.8-10.6 eV. The fact that the
linear dependence )( 0,, gBABA EEkC holds for p-
СuInSe2 crystals and their AIIBVI analogs suggests that
the obtained BAC , coefficients are determined correctly
and reliably.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 3. P. 302-308.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
305
Fig. 3. Temperature dependence of the total Hall mobility
for holes in р-CuInSe2. The curve numbering is discussed in
the text. Error bars illustrate precision of the experiment.
Fig. 2. Dependence of CA (line 1) and CB (line 2) coefficients
from (1) on the bandgap of p-СuInSe2 crystals and their AIIBVI
analogs. The arrows mark the refined CA for CdSe and CdS,
which fits the linear dependence CA = 6.3410-2(4.15 – Eg) eV∙Å.
Table 2. Coefficients CA,B for p-СuInSe2 and their AIIBVI
analogs (eV∙Å units).
M
at
er
ia
l
p-
C
uI
nS
e 2
ou
r
da
ta
p-
C
dS
e
da
ta
[1
5]
/
re
fi
ne
d
p-
C
dS
da
ta
[1
5]
/
re
fi
ne
d
p-
Z
nO
da
ta
f
ro
m
[1
5]
CA 0.200 0.230/0.150 0.082/0.105 0.051
CB 0.144 0.114 0.070 0.035
Concerning the temperature behavior of kinetic
coefficients in р-CuInSe2, our calculations show that the
carrier contribution to the valence band 7 is negligibly
small in comparison with that of the holes populating
6 and 7 bands. Let us consider the system with a
single acceptor level formed by interstitial selenium
atoms [20] with the concentration Na ≈ 4.0×1018 cm-3 and
depth EV + 0.019±0.002 eV correlating with the data
from [21]. We performed calculations for this system by
using carrier effective masses calculated for either of C1
and C2 cases (10), (11). The results revealed good
agreement between theoretical and experimental [9]
results concerning the temperature dependence of the
Hall coefficient R = f(1/T). The calculated thermal
voltage degenerates into a scalar value, fitting the
experimental data [9] within the precision limits of the
experimental measurements.
Solid and dashed curves in Figure 3 present
calculation results for the cases D1 and D2, respectively.
The curves designated numbers with primes 1', 2' were
obtained for 0, BAC . The temperature dependence of
the total Hall mobility for holes uH(T) in р-CuInSe2
crystals for the different experimental results are shown
with circles (data [24]) and triangles (data [25]).
Comparing the results presented by curves 1 and 1' with
2 and 2', one can see that for the case when non-
parabolicity of E(k) is neglected, one obtains the excess
mobility and markedly different shape of the curve
uH(T). For 0, BAC , the calculated and experimental
curves for uH(T) fit each other well for the temperatures
170 K ≤ T ≤ 350 K. The existing mismatch between
theory and experiment for uH(T) in р-CuInSe2 crystals
under Т < 150 K may stem from neglecting the hopping
scattering, which becomes quite significant at these
temperatures [20]. Under the temperature increase from
100 to 300 K the contribution of non-parabolicity into
the hole mobility was calculated using the masses (10),
(11) and the experimental data [24, 25]. We observed a
decrease of aforementioned contribution for
approximately 33 percents (from ≈50 % at 100 K to
≈ 17 % at 300 K), which is illustrated at the inset to
Fig. 2 for the parameter /)0((/ ,H BACuuu
%100)1)0( ,H BACu . The resulting difference
between the values of the total mobility calculated using
D1 and D2 effective hole masses for р-CuInSe2 (the
corresponding solid and dashed curves in Fig. 2) are
within the experimental precision. Due to this, it is hard
to say which set of CBAm ,,
||, (D1 or D2) is preferable for
the description of temperature variation of the kinetic
coefficients in р-CuInSe2.
To solve this problem, we used the experimental
spectrum [26] for imaginary part ki of the refraction
coefficient n of CuInSe2, measured for different
polarizations ||,i regarding the main crystalline axis
and the incident light wave with a wavelength . The
knowledge of the latter allowed us to apply the formula
[26]
/4 ii k (12)
to determine the components of absorption coefficient
i. On the other hand [20], the expression for i at the
fundamental absorption edge in semiconductor material
can be written as:
gii EAn , (13)
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 3. P. 302-308.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
306
where
2
,,
2/3
2
2
0
2/3
)()/2(
6
n
i
CBAn
n
iri Mmm
e
V
mc
A
. (14)
Here n is the carrier concentration, is the
photon energy,
n
i
e
i
n
ir mmm
111
describes the і-th
component of the reduced mass of electron-hole pair
( e
im is the і-th component of effective mass tensor for
conduction band electrons), n
iM are matrix elements for
optical transitions (6), V is the volume of the crystal, е is
the elementary charge, and 0 is the absolute dielectric
permittivity.
Calculating D1 and D2 effective masses for the
holes (Table 1) and using electron effective masses (for
CuInSe2 – ,10.0/ mm 11.0/|| mm [24], for CdSe
– ,13.0/ mm 14.0/|| mm [15], for CdS –
,21.0/ mm 22.0/|| mm [15] and for ZnO –
,30.0/ mm 31.0/|| mm [27]), we calculated
dimensionless variable ||,
2
2/3
0* 6
||,
A
e
mc
V
A
as a
function of semiconductor bandgap Eg (Fig. 4).
As it can be seen from the figure, the dependence
)(*
||, gEfA can be quite well described within
experimental precision for CBAm ,,
||, , cr and so as
)/( ||,
2
||,
*
||, gg EEA . (15)
Fig. 4. *
||A (1) and *
A (2) coefficients as the function of Eg
for р-CuInSe2 and its AIIBVI analogs (solid and dashed curves
correspond to D1 and D2 hole masses, respectively). The inset
shows the ratio
AA /*
|| with variation of the parameter С1:
line 1 – for the masses (11) and line 2 – for the masses (10).
The error bars illustrate dispersion of the theoretical values
obtained for the different experimental data. The asterisk
denotes the experimental result for р-CuInSe2 [22].
For further calculations, one should use the
following values for ||, (in eV-1) and ||, (in eV):
for the case D1 (10) –
;28.4,83.9,03.8,65.11 |||| (16)
for the case D2 (11) –
32.2,22.7,47.10,20.14 |||| . (17)
As it follows from the latter formulas, the
components of absorption coefficient are bounded with
the proportion **
|||||| /// AAkk . According to
[26], the experimental ratio kk /|| for the case of the
fundamental absorption in CuInSe2 crystals varies within
the range 1.05 – 1.10. The same ratio, calculated
according from (15) using (16) and (17), would yield the
values 1.44 and 1.75 for the cases D1 and D2,
respectively. Therefore, the best fit of theoretical curves
to the experimental data regarding /|| ratio can be
attained by using the hole effective masses according to
the case D1 (formula (10)).
It was experimentally proven [28, 29] that in quasi-
cubic model approximation for the crystals with
chalcopyrite structure [30] illuminated by light wave
with the polarization vector perpendicular to the main
optical axis of the crystal, the ratio of intensity peak in
electro-reflection spectra ( ||I and I ) obeys the
following expressions:
2
,
|||| )/3/2(9,0 so
CBA
E
I
I
I
I
(18)
with
crsocrsocrsoE
3
8
)(5.0 2 . (19)
The discussed peaks correspond to electron
transitions from the valence to conduction band in the
crystals AIIBIVCV
2. It is worth noting that for the limit
case 0so the ratio soE / tends to 2/3. Taking
into account (5), (6), one can show that for the crystals
with С1 > 1
1
||
1
|| /2,2 C
I
I
C
I
I
BC
. (20)
For the case С1 < 1, the subscripts “В” and “С”
should be swapped in (20).
In this way, one can treat the ratio /|| = AA /||
as a function of the parameter С1 for the crystals with
chalcopyrite or wurtzite structure. The inset to Fig. 4
proves that the dependence
%100)0(/)0(/ *
||
*
||
AAAA is linear and equal to
(81)С1 or (212)С1 for the hole masses calculated for
the cases D1 and D2. Experimental data on this ratio for р-
CuInSe2 (shown as the asterisk in the inset to Fig. 4) fits
better to the case when the effective mass estimations are
done with the formula (10). The obtained correlations
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 3. P. 302-308.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
307
between ||,A and their ratio for the different wurtzite and
chalcopyrite crystals (e.g., CuInSe2, CdSe, CdS and ZnO,
see Fig. 4) suggests that the most accurate description of
the effective mass tensor for р-CuInSe2 is that provided
with the formulas (10).
4. Conclusions
We show that p-CuInSe2 crystals with the components of
hole effective mass tensor obeying the symmetry
relations (3) is characterized with two sets of CBAm ,,
||, ,
describing temperature dependence of the total
conductivity, Hall coefficient and thermal voltage within
experimental precision. For the upper valence sub-bands
6 and 7 , we have estimated the coefficients BAC ,
characterizing deviation of the dispersion relation E(k)
from its parabolic form, which yielded an acceptable
agreement of the calculated and experimental
temperature dependences for the kinetic coefficients in
this material. It was found that )( 0,, gBABA EEkC for
p-СuInSe2 and their AIIBVI analogs, allowing to refine
the values of AC for CdSe and CdS. We also obtained a
phenomenological expression (15) for the coefficients
||,A in formula (13) describing the spectral dependence
of light absorption tensor close to the fundamental
absorption edge as a function of Eg. Moreover, the
dependence %100)0(/)0(/ *
||
*
||
AAAA = 1Cf
proved to be linear in the first approximation for CdSe,
CdS, ZnO and CuInSe2 with wurtzite and chalcopyrite
structure; the experimental data known for р-CuInSe2 fits
reasonably our theoretical calculations performed for the
components of the effective masses given by the
formula (10).
The obtained effective mass values make it
possible to properly explain the component anisotropy
for the interband light absorption tensor, as well as the
experimental data on temperature dependence of the
kinetic coefficients within p-CuInSe2 in the temperature
range 100 – 350 K.
Acknowledgements
The paper was partially supported by the budget
financing of the Ministry for Education and Science of
Ukraine and research projects (2009-2011 years) at the
Department of Electronics and Energy Engineering and
Scientific and Educational Center “Material Science of
Semiconductors and Energy-Efficient Technologies” at
the Chernivtsi National University.
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