Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts
We investigated temperature dependence of contact resistance of an Au−Ti−Pd₂Si ohmic contact to heavily doped n⁺ -Si. The contact resistance increases with temperature owing to conduction through the metal shunts. In this case, the limiting process is diffusion input of electrons to the metal sh...
Saved in:
| Date: | 2010 |
|---|---|
| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2010
|
| Series: | Semiconductor Physics Quantum Electronics & Optoelectronics |
| Online Access: | https://nasplib.isofts.kiev.ua/handle/123456789/118737 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Cite this: | Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts / A.E. Belyaev, N.S. Boltovets, R.V. Konakova, Ya.Ya. Kudryk, A.V. Sachenko, V.N. Sheremet // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 4. — С. 436-438. — Бібліогр.: 7 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
nasplib_isofts_kiev_ua-123456789-118737 |
|---|---|
| record_format |
dspace |
| spelling |
nasplib_isofts_kiev_ua-123456789-1187372025-06-03T16:26:26Z Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts Belyaev, A.E. Boltovets, N.S. Konakova, R.V. Kudryk, Ya.Ya. Sachenko, A.V. Sheremet, V.N. We investigated temperature dependence of contact resistance of an Au−Ti−Pd₂Si ohmic contact to heavily doped n⁺ -Si. The contact resistance increases with temperature owing to conduction through the metal shunts. In this case, the limiting process is diffusion input of electrons to the metal shunts. The proposed mechanism of contact resistance formation seems to realize also in the case of wide-gap semiconductors with high concentration of surface states and dislocation density in the contact. 2010 Article Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts / A.E. Belyaev, N.S. Boltovets, R.V. Konakova, Ya.Ya. Kudryk, A.V. Sachenko, V.N. Sheremet // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 4. — С. 436-438. — Бібліогр.: 7 назв. — англ. 1560-8034 PACS 73.40.Cg, 73.40.Ns, 85.30.-z https://nasplib.isofts.kiev.ua/handle/123456789/118737 en Semiconductor Physics Quantum Electronics & Optoelectronics application/pdf Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| description |
We investigated temperature dependence of contact resistance of an
Au−Ti−Pd₂Si ohmic contact to heavily doped n⁺
-Si. The contact resistance increases with
temperature owing to conduction through the metal shunts. In this case, the limiting
process is diffusion input of electrons to the metal shunts. The proposed mechanism of
contact resistance formation seems to realize also in the case of wide-gap semiconductors
with high concentration of surface states and dislocation density in the contact. |
| format |
Article |
| author |
Belyaev, A.E. Boltovets, N.S. Konakova, R.V. Kudryk, Ya.Ya. Sachenko, A.V. Sheremet, V.N. |
| spellingShingle |
Belyaev, A.E. Boltovets, N.S. Konakova, R.V. Kudryk, Ya.Ya. Sachenko, A.V. Sheremet, V.N. Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Belyaev, A.E. Boltovets, N.S. Konakova, R.V. Kudryk, Ya.Ya. Sachenko, A.V. Sheremet, V.N. |
| author_sort |
Belyaev, A.E. |
| title |
Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts |
| title_short |
Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts |
| title_full |
Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts |
| title_fullStr |
Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts |
| title_full_unstemmed |
Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts |
| title_sort |
temperature dependence of contact resistance of au−ti−pd2si−n⁺ -si ohmic contacts |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2010 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/118737 |
| citation_txt |
Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts / A.E. Belyaev, N.S. Boltovets, R.V. Konakova, Ya.Ya. Kudryk, A.V. Sachenko, V.N. Sheremet // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 4. — С. 436-438. — Бібліогр.: 7 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
AT belyaevae temperaturedependenceofcontactresistanceofautipd2sinsiohmiccontacts AT boltovetsns temperaturedependenceofcontactresistanceofautipd2sinsiohmiccontacts AT konakovarv temperaturedependenceofcontactresistanceofautipd2sinsiohmiccontacts AT kudrykyaya temperaturedependenceofcontactresistanceofautipd2sinsiohmiccontacts AT sachenkoav temperaturedependenceofcontactresistanceofautipd2sinsiohmiccontacts AT sheremetvn temperaturedependenceofcontactresistanceofautipd2sinsiohmiccontacts |
| first_indexed |
2025-11-27T05:43:04Z |
| last_indexed |
2025-11-27T05:43:04Z |
| _version_ |
1849921049637945344 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 4. P. 436-438.
PACS 73.40.Cg, 73.40.Ns, 85.30.-z
Temperature dependence of contact resistance
of Au−Ti−Pd2Si−n+-Si ohmic contacts
A.E. Belyaev1, N.S. Boltovets2, R.V. Konakova1, Ya.Ya. Kudryk1, A.V. Sachenko1, V.N. Sheremet
1V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine
41, prospect Nauky, 03028 Kyiv, Ukraine
Phone: (380-44) 525-61-82; fax: (380-44) 525-83-42; e-mail: konakova@isp.kiev.ua
2State Enterprise Research Institute “Orion”, 8a Eugene Pottier St., Kyiv, 03057, Ukraine
Abstract. We investigated temperature dependence of contact resistance of an
Au−Ti−Pd2Si ohmic contact to heavily doped n+-Si. The contact resistance increases with
temperature owing to conduction through the metal shunts. In this case, the limiting
process is diffusion input of electrons to the metal shunts. The proposed mechanism of
contact resistance formation seems to realize also in the case of wide-gap semiconductors
with high concentration of surface states and dislocation density in the contact.
Keywords: wide-gap semiconductor, ohmic contact, contact resistance.
Manuscript received 01.11.10; accepted for publication 02.12.10; published online 30.12.10.
1. Introduction
In the last few years, some reports have appeared on
anomalous temperature dependence of contact resistance
Rc (growth with temperature) of ohmic contacts to
semiconductors with high dislocation density [1-3]. It
should be noted that such behavior of Rc (T) curves
cannot be explained by the classical mechanisms of
current transport (thermionic, thermal-field, tunnel) in
the Schottky contacts. The authors of the above papers
related the obtained Rc (T) dependences to conduction
through the metal shunts linked to dislocations.
In the present work, we describe growing with
temperature dependences of contact resistance (measured
in the 80−380 K temperature range) that take place in
ohmic contacts to heavily doped silicon.
To explain them, we also apply the mechanism of current
transport through metal shunts. It is supposed that the
limiting process is the mechanism of diffusion input of
electrons to those metal shunts. The theoretical
estimations showed that, in the case of heavily doped
semiconductor material, such a limitation is possible only
if accumulation band bending is realized in the
semiconductor near the metal shunt ends. Such a situation
seems rather realistic if one takes into account both the
edge effect (leading to big increase of the electric field
strength) and mirror image forces. In our case, not only a
big decrease of barrier height near the shunt edge occurs
but the band bending changes its sign as well.
SiPdTiAu 2−−
We calculated contact resistance, with current
limiting mechanism of diffusion input of electrons, by
assuming that a rather high barrier is realized in the
regions far from dislocations, so that it is possible to
neglect current transport through the above regions. In
that case, the contact resistance Rc can be determined
from the derivative of the current through all
dislocations.
The density of the thermionic current Jnc flowing
through the contact at the site of dislocation outlet can be
determined by solving the continuity equation for
electrons. With allowance made for the diffusion
limitation, the contact resistance related to a single
dislocation, Rc0, is (in the case of a nondegenerate
semiconductor)
0
0
4
4
1
0
c
D
c
y
d
T
L
y
n
T
c
eNqV
e
D
V
q
kTR
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
=
α
. (1)
Here k is the Boltzmann constant, Т temperature, q
electron charge, VT mean thermal velocity of electrons,
Dn electron diffusion coefficient, yc0 dimensionless
equilibrium band bending at the site of dislocation
outlet, α numerical coefficient (of the order of unity), LD
Debye shielding length, and Nd donor concentration in
the semiconductor.
If the semiconductor is degenerate and the current
limitation due to the diffusion input takes place, one can
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
436
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 4. P. 436-438.
50 100 150 200 250 300 350 400
0
2
4
6
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
8
10
12
ρ c,
·1
0-6
·c
m
2
T,K
1
2
Ω
also use Eq. (1). In that case, however, the following
relation between the diffusion coefficient Dn and
electron mobility μn has to be used:
also use Eq. (1). In that case, however, the following
relation between the diffusion coefficient Dn and
electron mobility μn has to be used:
1
)(ln
−
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
μ=
zd
nd
q
kTD nn . (2)
Here is the dimensionless Fermi
energy, and n is the electron concentration in the
semiconductor bulk:
kTEz f /=
( )∫
∞
−+
⎟
⎠
⎞
⎜
⎝
⎛
π
=
0
5.1
exp1300
2 dx
zx
xTNn c , (3)
where Nc is the effective density of states in the
conduction band at Т = 300 K. The area from which the
current flowing through a single dislocation is collected
equals , where 2
DLπ
Fig. 1. The temperature dependences of contact resistivity
ρc for Au−Ti−Pd2Si−n+-Si ohmic contact (filled squares –
experiment, curves – theory). Curve 1 (2) is plotted
for Nd = 1019 cm-3 (3×1019 cm-3). The values of parameters
used in calculation: VT = 107 cm/s; curve 1: yc0 = 2.7;
ND1 = 2.8×109 cm-2; curve 2: yc0 = 1.5; ND1 = 5×109 cm-2. ( ) 2/1'
2/1
5.0
2
0 )(
2
−
Φ⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛ εε
= z
Nq
Tk
L
c
s
D (4)
is the Debye shielding length at an arbitrary degree of
semiconductor degeneracy, vacuum
(semiconductor) permittivity, and
( )sεε 0
( )
( )( )∫
∞
−+
−
π
=Φ
0
2
'
2/1 exp1
exp2)( dx
zx
zxxz . (5)
The contact resistance for a contact of unit area
determined by the mechanism of diffusion input is
1
2
0
diff
DD
c
NL
R
R
π
= , (6)
where Nd1 is the density of dislocations that take part in
current transport. In general, Nd1 is not equal to the
density of dislocations that take part in electron
scattering, Nd2. The current transport is related to the
dislocations that are normal to the contact plane, while
scattering occurs at those dislocations that are oriented at
an angle to the contact plane.
The quantity (S is the contact area) has
a meaning of the total area from which the current
flowing through all dislocations is collected. As a rule,
the value of is much less than unity, even at
maximal dislocation densities (about ),
except the case of weakly doped semiconductors
( ).
SNL DD 1
2π
1
2
DD NLπ
21110 cm1010 −−
315 cm10 −≤dN
The electron diffusion coefficient Dn was
determined with fitting procedure using Eqs. (2) and (3),
while the temperature dependence of electron mobility
μn, when comparing the calculated and experimental
dependences, was taken from [4] for the doping level of
. The rated resistivity ρ319 cm108.2 −× Si of silicon
samples used to make ohmic contacts was 0.002 Ω⋅cm.
Taking into account its standard spread and the fact that
predominant scattering at Т = 300 K is that on the
charged impurities (as a result, the dependence of ρSi on
the doping level is very weak), one can determine the
limits for variation of donor concentration in the samples
studied: ( ) 31919 cm10310 −×− . So we used both
limiting values for donor concentration when plotting
Fig. 1.
Shown in Fig. 1 are the experimental temperature
dependence of contact resistivity for Au−Ti−Pd2Si−n+-Si
ohmic contact с ρSi = 0.002 Ω⋅cm and ρc (T) curves
calculated for two donor concentrations: and
. The contact metallization was made using
layer-by-layer vacuum thermal sputtering of metals onto
an n
319 cm10 −
319 cm103 −×
+-silicon substrate heated up to 330 °C. The ohmic
contact was formed by the Pd2Si phase that appeared in a
thin near-surface layer of in the course of
palladium sputtering. Because of misfit of Pd
Si−+n
2Si and Si
lattices and coefficients of thermal expansion, high
density of structural defects (in particular, dislocations)
is formed in the near-surface layer of [5-7].
According to [1-3], metal shunts (that short-circuit the
space charge region) may form at the above defects. One
should note very good agreement between the theory and
experiment. It was obtained by using the general
Eqs. (2)–(5) that take into account degeneracy of
semiconductor.
Si−+n
The mechanism of contact resistance formation
proposed in the present work for metal−semiconductor
contacts has to realize, first of all, in the case of wide-
gap semiconductors with high concentration of surface
states in the contact. It looks rather paradoxical because
current is transported through the regions accumulating
electrons rather than the depletion regions. At the same
time, the practically ideal agreement between the
437
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 4. P. 436-438.
calculated and experimental temperature dependences of
contact resistivity is indicative of the validity of the
above mechanism. One should note that, in the model
proposed in [1-3], the temperature dependence of contact
resistance was strictly linear.
References
1. T.V. Blank, Yu.A. Gol’dberg, O.V. Konstantinov,
V.G. Nikitin, E.A. Posse, Peculiarities in the
mechanism of current flow through an ohmic
contact to gallium phosphide // Technical Physics
Letters 30(19), p. 806-809 (2004).
2. T.V. Blank, Yu.A. Gol’dberg, Mechanisms of
current flow in metal-semiconductor ohmic
contacts // Semiconductors 41(11), p. 1263-1292
(2007).
3. V.N. Bessolov, T.V. Blank, Yu.A. Gol’dberg,
O.V. Konstantinov, E.A. Posse, Dependence of the
mechanism of current flow in the in n-GaN alloyed
ohmic contact on the majority carrier concentration
// Semiconductors 42(11), p. 1315-1317 (2008).
4. V.I. Fistul’, Heavily Doped Semiconductors.
Nauka, Moscow (1967), in Russian.
5. A.E. Gershinsky, A.V. Rzhanov, E.I. Cherepov,
Thin-film silicides in microelectronics // Mikro-
elektronika 11(2), p. 83-94 (1982), in Russian.
6. P.E. Schmid, P.S. Ho, H. Foll, G.W. Rubloff,
Electronic states and atomic structures at the
Pd2Si−Si interface // J. Vac. Sci. Technol. 18(3),
p. 937-943 (1981).
7. V.M. Ievlev, S.B. Kushev, A.V. Bugakov,
S.A. Soldatenko, B.N. Markushev, I.G. Rudneva,
Conjugation regularities and substructure of
interphase boundaries in the Si−Me silicide systems
(Me: Pt, Pd, Ni, Re, Ir, Mo, Ti) // Proc. ISFTE-12,
Kharkov, Ukraine, 2002, p. 201-206.
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
438
|