Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP
Presented in this paper are experimental data on structural properties of contact metallization and temperature dependence of the specific contact resistance for ohmic contacts Au–Ti–Pd–n⁺-InP and Au–Ti–Ge–Pd-n⁺-InP prepared using the method of successive thermal evaporation of metals in oil-free va...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2015
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| Cite this: | Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP / A.E. Belyaev, N.A. Boltovets, A.B. Bobyl, V.P. Kladko, R.V. Konakova, Ya.Ya. Kudryk, M.U. Nasyrov, A.V. Sachenko, V.S. Slipokurov, A.S. Slepova, N.V. Safryuk, A.I. Gudymenko, V.V. Shynkarenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 4. — С. 391-395. — Бібліогр.: 18 назв. — англ. |
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nasplib_isofts_kiev_ua-123456789-1212592025-02-09T16:26:53Z Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP Belyaev, A.E. Boltovets, N.A. Bobyl, A.B. Kladko, V.P. Konakova, R.V. Kudryk, Ya.Ya. Nasyrov, M.U. Sachenko, A.V. Slipokurov, V.S. Slepova, A.S. Safryuk, N.V. Gudymenko, A.I. Shynkarenko, V.V. Presented in this paper are experimental data on structural properties of contact metallization and temperature dependence of the specific contact resistance for ohmic contacts Au–Ti–Pd–n⁺-InP and Au–Ti–Ge–Pd-n⁺-InP prepared using the method of successive thermal evaporation of metals in oil-free vacuum in one process cycle onto the n⁺-n-n⁺⁺-n⁺⁺⁺-InP epitaxial structure heated to 300 °C. It has been theoretically and experimentally shown that within the temperature range 250…380 K the current transport mechanism in the ohmic contacts Au–Ti–Pd–n⁺-InP is thermal-field one, and in the ohmic contacts Au–Ti–Ge–Pd-n⁺-InP it is caused by conductivity along metal shunts linked with dislocations. According to the X-ray diffraction data, the density of these dislocations in the near-contact InP area is ~10⁹ cm⁻². 2015 Article Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP / A.E. Belyaev, N.A. Boltovets, A.B. Bobyl, V.P. Kladko, R.V. Konakova, Ya.Ya. Kudryk, M.U. Nasyrov, A.V. Sachenko, V.S. Slipokurov, A.S. Slepova, N.V. Safryuk, A.I. Gudymenko, V.V. Shynkarenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 4. — С. 391-395. — Бібліогр.: 18 назв. — англ. 1560-8034 DOI: 10.15407/spqeo18.04.391 PACS 73.40.Ns https://nasplib.isofts.kiev.ua/handle/123456789/121259 en Semiconductor Physics Quantum Electronics & Optoelectronics application/pdf Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Presented in this paper are experimental data on structural properties of contact metallization and temperature dependence of the specific contact resistance for ohmic contacts Au–Ti–Pd–n⁺-InP and Au–Ti–Ge–Pd-n⁺-InP prepared using the method of successive thermal evaporation of metals in oil-free vacuum in one process cycle onto the n⁺-n-n⁺⁺-n⁺⁺⁺-InP epitaxial structure heated to 300 °C. It has been theoretically and experimentally shown that within the temperature range 250…380 K the current transport mechanism in the ohmic contacts Au–Ti–Pd–n⁺-InP is thermal-field one, and in the ohmic contacts Au–Ti–Ge–Pd-n⁺-InP it is caused by conductivity along metal shunts linked with dislocations. According to the X-ray diffraction data, the density of these dislocations in the near-contact InP area is ~10⁹ cm⁻². |
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| author |
Belyaev, A.E. Boltovets, N.A. Bobyl, A.B. Kladko, V.P. Konakova, R.V. Kudryk, Ya.Ya. Nasyrov, M.U. Sachenko, A.V. Slipokurov, V.S. Slepova, A.S. Safryuk, N.V. Gudymenko, A.I. Shynkarenko, V.V. |
| spellingShingle |
Belyaev, A.E. Boltovets, N.A. Bobyl, A.B. Kladko, V.P. Konakova, R.V. Kudryk, Ya.Ya. Nasyrov, M.U. Sachenko, A.V. Slipokurov, V.S. Slepova, A.S. Safryuk, N.V. Gudymenko, A.I. Shynkarenko, V.V. Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Belyaev, A.E. Boltovets, N.A. Bobyl, A.B. Kladko, V.P. Konakova, R.V. Kudryk, Ya.Ya. Nasyrov, M.U. Sachenko, A.V. Slipokurov, V.S. Slepova, A.S. Safryuk, N.V. Gudymenko, A.I. Shynkarenko, V.V. |
| author_sort |
Belyaev, A.E. |
| title |
Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP |
| title_short |
Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP |
| title_full |
Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP |
| title_fullStr |
Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP |
| title_full_unstemmed |
Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP |
| title_sort |
structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -inp |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2015 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/121259 |
| citation_txt |
Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP / A.E. Belyaev, N.A. Boltovets, A.B. Bobyl, V.P. Kladko, R.V. Konakova, Ya.Ya. Kudryk, M.U. Nasyrov, A.V. Sachenko, V.S. Slipokurov, A.S. Slepova, N.V. Safryuk, A.I. Gudymenko, V.V. Shynkarenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 4. — С. 391-395. — Бібліогр.: 18 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
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2025-11-27T22:35:38Z |
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| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 391-395.
doi: 10.15407/spqeo18.04.391
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
391
PACS 73.40.Ns
Structural and electrical-physical properties
of the ohmic contacts based on palladium
to n
+
-n-n
++
-n
+++
-InP
A.E. Belyaev
1
, N.A. Boltovets
2
, A.B. Bobyl
3
, V.P. Kladko
1
, R.V. Konakova
1
,
Ya.Ya. Kudryk
1
, M.U. Nasyrov
1
, A.V. Sachenko
1
, V.S. Slipokurov
1
,
A.S. Slepova
2
, N.V. Safryuk
1
, A.I. Gudymenko
1
, V.V. Shynkarenko
1
1
V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
41, prospect Nauky, 03680 Kyiv, Ukraine, e-mail: konakova@isp.kiev.ua
2
State Enterprise Research Institute “Orion”, 03057 Kyiv, Ukraine
3
A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences,
197101, St. Petersburg, Russian Federation
Abstract. Presented in this paper are experimental data on structural properties of contact
metallization and temperature dependence of the specific contact resistance for ohmic
contacts Au–Ti–Pd–n
+
-InP and Au–Ti–Ge–Pd-n
+
-InP prepared using the method of
successive thermal evaporation of metals in oil-free vacuum in one process cycle onto
the n
+
-n-n
++
-n
+++
-InP epitaxial structure heated to 300 °C. It has been theoretically and
experimentally shown that within the temperature range 250…380 K the current
transport mechanism in the ohmic contacts Au–Ti–Pd–n
+
-InP is thermal-field one, and in
the ohmic contacts Au–Ti–Ge–Pd-n
+
-InP it is caused by conductivity along metal shunts
linked with dislocations. According to the X-ray diffraction data, the density of these
dislocations in the near-contact InP area is ~10
9
cm
–2
.
Keywords: ohmic contacts, specific contact resistance, InP, current transport mechanism.
Manuscript received 09.06.15; revised version received 10.09.15; accepted for
publication 28.10.15; published online 03.12.15.
1. Introduction
Indium phosphide is one of the main semiconductor
materials currently used for manufacturing Gunn diodes
and field-effect transistors with high mobility – high-
electron mobility transistor (HEMT) of millimeter and
submillimeter wavelengths [1-4]. These devices are
characterized with very small dimensions. Therefore, it
is natural to demand high structural homogeneity to
forming contact layers and the interface metal-InP. This
requirement applies equally to both rectifying (barrier)
and nonrectifying (ohmic) contacts. For ohmic contacts
to the indium phosphide microwave devices, gold-
germanium eutectic is most often used.
For all the merits of such contact (it is known since
the first experiments on GaAs Gunn diode [5]), the
presence of interfacial interactions, which are
accompanied by formation of a number of new phases
that originate in the process of formation of ohmic
contacts and possible overloads in the operation of
devices in electronic sets, causes significant
heterogeneity of the interface ‘forming contact layer –
InP’. In this case, the phases originating at relatively low
temperatures do not break down at higher ones, too [6].
It leads to a non-uniform distribution of the current
density over the contact area. In addition, the
heterogeneity in the height of the barrier arises [7]. I.e.,
the layered structure not only of contact metallization,
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 391-395.
doi: 10.15407/spqeo18.04.391
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
392
but the area of the interface ‘forming contact layer – InP’
is significantly broken. Therefore, still there is a
necessity to search for optimizing the parameters of the
ohmic contacts to InP and methods of their
manufacturing [8-10].
For example, formation of the contact metallization
to InP with the first deposited metal layer, contributing
to improvement of adhesion. This layer is called as
adhesive one having oxidation resistance and relatively
low temperature of reaction with InP, which should
provide adhesion. Annealing of the contact metallization
with the adhesive layer within the temperature range
300 to 450 °C results in formation of an ohmic contact.
Thus, when preparing the ohmic contact Pd–n-InP
(n ≈ 10
17
cm
–3
) using electron-beam evaporation,
followed by annealing within the temperature range
300…375 °C, a minimum specific contact resistivity of
~4.2∙10
–6
Ohm∙сm
2
was obtained [11].
When creating the ohmic contact Au–Ge–Pd–n-InP
(n ≈ 10
17
cm
–3
) by using the same technological process,
but with annealing within the temperature range
350…450 °C, the minimum value ρc was close to
2.5∙10
–6
Ohm∙сm
2
[11]. At the same time, up to date for
these contacts a number of important physical and
technological parameters have not been studied,
including temperature dependences of ρc, influence of
structural defects that originate during annealing and
cooling the samples in the area of the interface ‘forming
contact layer – InP’ due to relaxation of internal
mechanical strains on the value ρc and dependence
ρc (T). We also note a particular interest of developers of
technology for devices based on A
3
B
5
compounds to the
reduction of the number of heat treatments, which, on
the one hand, reduces the cost of production of devices
and, on the other hand, improves the quality of the active
elements. Currently, non-annealed ohmic contacts are
used in the technological process of creation of HEMT
based on the compounds A3N [12].
Below, the research of ohmic contacts based on
palladium to the epitaxial structure n
+
-n-n
++
-n
+++
-InP is
presented. The ohmic contacts Au–Ti–Pd–n
+
-InP and
Au–Ti–Ge–Pd–n
+
-InP were created to the upper
epitaxial n
+
-layer InP.
2. Samples and research methods
There were investigated two types of the samples: the
test structures for measuring specific contact resistivity
ρc within the temperature range 250…380 K with the use
of transmission line method (TLM) and the test
structures with continuous metallization for measuring
the profile of distribution of the components as well as
phase composition of the contact metallization by the
methods of Auger electron spectroscopy and X-ray
diffractometry, respectively. The elemental composition
was measured using Auger spectrometer LAS-2000, the
phase composition and deformation effects – setup ARL
X’Tra (Thermo scientific) with CuKα radiation and
database ICDD, PDF-2 Release 2012.
Ohmic contacts were formed using the method of
successive thermal deposition of metals in oil-free va-
cuum in a single processing cycle onto heated to 300 °C
substrate that is epitaxial structure n
+
-n-n
++
-n
+++
-InP
obtained using gas-phase epitaxy. The structure
parameters are the concentration of the donor impurity
(Si) in the layers: n
+
– 10
18
cm
–3
, n – 8∙10
15
cm
–3
, n
++
–
5∙10
17
cm
–3
, n
+++
– 2∙10
18
cm
–3
, the thicknesses of the
layers: 0.2, 15, 3, and 300 μm, respectively. The ohmic
contacts Au (100 nm)–Ti (40 nm)–Pd (30 nm)–n
+
-InP
and Au(200 nm)–Ti(40 nm)–Ge(60 nm)–Pd(30 nm)–
n
+
-InP were formed during the deposition process and
not subjected to the additional annealing.
3. Experimental results and discussion
Figs 1 and 2 shows the profiles of distribution of the
components in the contact metallization Au–Ti–Pd–
n
+
-InP and Au–Ti–Ge–Pd–n
+
-InP formed on the heated
to 300 °C substrates. As seen from these figures, both
types of contacts have a layered structure. In both cases,
the increased content of oxygen and carbon in the
titanium film is observed. For the sample Au–Ti–Ge–
Pd–n
+
-InP (Fig. 2), typical is the mass transport of Ge
into the thin near-contact area of InP, which causes the
increase in the concentration of the donor impurity (Ge
is the donor in InP [13]) in this area. The peculiarity of
the near-contact area of InP in both samples is its
multicomponent character, as can be seen from Figs 1
and 2.
The XRD analysis of the test structures with both
types of metallization has shown the presence of
reflections from the polycrystalline Au and Ti films
(Figs 3 and 4) and absence of corresponding reflections
from Ge and Pd or their compounds with InP. As Pd and
Ge are observed in the corresponding profiles of the
contact metallization to n
+
-InP (Figs 1 and 2), it can be
assumed that during deposition of metal on a heated to
300 °C substrate, the products of the phase formation are
created in the amorphous phase. This assumption does
not contradict the available data in the literature about
the ohmic contacts to InP based on palladium [11, 14].
Fig. 1. Profiles of component distribution in the contact
metallization Au–Ti–Pd–n+-InP.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 391-395.
doi: 10.15407/spqeo18.04.391
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
393
0 5 10 15 20 25
0
10
20
30
40
50
60
70
80
90
100
A
t.
%
Sputtering time, min
Au
Ti
Ge
In
P
Pd
COC
O
Fig. 2. Profiles of component distribution in the contact
metallization Au–Ti–Ge–Pd–n+-InP.
The analysis of diffraction spectra indicates the
difference in the elastic-strain state of two contact
systems. In particular, for the system Au–Ti–Pd–n
+
-InP
(Fig. 3), the values of deformations in the contact
metallization is about 0.014, while for the system Au–
Ti–Ge–Pd–n
+
-InP (Fig. 4) this value is lower; i.e., the
contact Au–Ti–Ge–Pd–n
+
-InP is more relaxed [15, 16].
The analysis of the deformation state of the contact
systems shows that the main mechanism of relaxation of
strains in the system Au–Ti–Ge–Pd–n
+
-InP is generation
of dislocations in the near-contact area of InP with the
density of the order of 10
9
cm
–2
. It is these defects of this
type that are the main cause of the structural
heterogeneity in the near-contact area.
The voltage-current characteristics of the contacts
Au–Ti–Pd–n
+
-InP and Au–Ti–Ge–Pd–n
+
-InP within the
temperature range 250…380 K were linear. The
temperature dependences ρc to these contacts measured
within the temperature range 250…380 K are shown in
Fig. 5. The analysis of the dependences ρc (T) showed
that for the ohmic contacts Au–Ti–Pd–n
+
-InP (empty
points in the curve 1, Fig. 5) thermal-field current
transport mechanism is characteristic, for Au–Ti–Ge–
Pd–n
+
-InP (filled points in the curve 2, Fig. 5) – the
current transport mechanism through metal shunts. In
what follows, they will be considered in more detail.
Let plot a relationship ρc (T) for ohmic contact Au–
Ti–Pd–n
+
-InP in accordance with the modified formula
for the thermal-field current transport mechanism [17]:
,
coth
exp
)(
cothcosh
F
00
00
F
F
0
*
0000
00
kT
E
kT
E
E
E
EqT
m
m
A
kT
E
kT
E
Ek
c
c
TF
(1)
where ρTF is the specific contact resistivity in the case of
the thermal-field current transport mechanism, k –
Boltzmann constant, T – temperature, q – elementary
charge, m
– effective mass of electron, m0 – free
electron mass, φc – potential energy of electron, i.e., the
barrier height at the interface metal-semiconductor,
5.020
000 )/7.11)(10/)(/(054.0 sdNmmE
–
characteristic energy of tunneling, εs – dielectric constant
of semiconductor, A – the Richardson constant, EF – the
Fermi energy, Nd – donor concentration. Indeed, as can
be seen from a comparison of the experimental and
theoretical dependences ρc (T) (Fig. 5, curve 1: dots –
experiment, line – calculation), they are in good
agreement with each other. The coincidence is achieved
in the case where the barrier height is 0.28 eV.
Fig. 3. Experimental diffraction pattern of the contact
metallization Au–Ti–Pd–n+-InP (upper curve) and calculated
diffraction patterns for Au and Ti (lower curves).
Fig. 4. Experimental diffraction pattern of the contact
metallization Au–Ti–Ge–Pd–n+-InP (upper curves) and
calculated diffraction patterns for Au and Ti (lower curves).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 391-395.
doi: 10.15407/spqeo18.04.391
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
394
250 300 350 400
0
5
10
15
c
,
·1
0
-5
·c
m
2
T, K
1
2
Fig. 5. Temperature dependence of the specific contact
resistance (1 – Au–Ti–Pd–n+-InP, 2 – Au–Ge–Ti–Pd–n+-InP,
dots – experiment, lines – calculation).
Since the literature data on the dependence ρc (T)
for ohmic contacts based on Pd are absent, let’s compare
the ρc values measured at room temperature [14] with
those obtained in our work. Thus, the ohmic
characteristics for contact Pd-InP were observed after
annealing at T = 300 °C and were caused by the presence
of the phase PdIn. For such a contact, the ρc value at
room temperature was about 6∙10
–5
Оhm∙сm
2
[14]. ρc of
the same order was obtained in our work after deposition
of metals (Pd, Au and Ti) onto the substrate heated to
300 °C (Fig. 5, curve 1).
Our data on ρc (T) as well as on the phase and
chemical composition of the contact metallization of
Au–Ti–Pd–n
+
-InP indicate relatively uniform interface
‘forming contact layer – InP’ created directly during
deposition of the contact metallization on the InP
substrate heated to 300 °C without subsequent heat
treatment.
The analysis of the ohmic contacts, in which the
composition together with the adhesion layer Pd
includes Ge, has shown that at room temperature for
different samples and annealing conditions, ρc varies
within the range 10
–5
…2.5∙10
–6
Ohm∙сm
2
according to
[14]. In our work (Fig. 5, curve 2), during deposition
of metals (Pd, Ge, Ti, and Au) on the heated to
300 °C substrate, at room temperature ρc is close to
1.2∙10
–5
Ohm∙сm
2
. I.e., as in the previous case (contact
Au–Ti–Pd–n
+
-InP), the ρc value is of the same order as
those of the samples, in which the ohmic contact has
formed after annealing.
In the theoretical simulation of the dependence
ρc (T) for the ohmic contact Au–Ti–Ge–Pd–n
+
-InP, we
take into account that in this case the subcontact layer
n
+
-InP is strongly degenerated due to subdoping with
germanium. As seen from Fig. 5 (curve 2), at T > 250 K
ρc (T) is linearly dependent on the temperature. In
accordance with [18], we assume that the current
transport occurs through the metal shunts linked with
dislocations. To calculate ρc (T), we use the expressions
[18] valid for the case of degenerated semiconductor.
Following [18], we write an expression for the specific
contact resistivity ρtw that is determined by the supply of
electrons from semiconductor into the ends of shunts for
the contact of unit area
00
2
D1 exp1ln
1
/ cD
tw
yzTmmALNq
k
, (2)
where ND1 is the density of conductive dislocations, LD –
Debye screening length, yc0 – dimensionless (normalized
to kT) contact potential. In the considered case, the
dimensionless Fermi energy z (normalized to kT) is
determined from the equation of volume neutrality:
0
2/3
0
)(exp1300
2
dx
zx
xT
NN cd , (3)
where Nс0 is the effective density of states in the
conduction band.
It should be noted that the stronger degenerated
semiconductor, the weaker the value ρtw depends on the
temperature, and with threshold levels of degeneration
when z + yc0 >> 1, the dependence ρtw is absent. Since
the resistivity of all the metal shunts ρsh is connected in
series with the resistivity ρtw in the case of degenerated
semiconductor, the relation for the total resistivity of the
ohmic contact in semiconductor with a high dislocation
density is written as
.shtwc (4)
Here, 1)( Dshsh NTR and
2
0 )(
)(
r
dT
TR D
sh
is the temperature dependence of the resistance of metal
shunt, where ρ0 is the specific resistivity, dD –
dislocation length, r – shunt radius (in the calculation, all
the shunts are considered to be identical). It is assumed
that the current flowing between dislocations can be
neglected in comparison with the current flowing
through these dislocations. It is provided by the large
value of the barrier formed between dislocations [18].
The temperature dependence ρsh (Т) with account of
the temperature dependence of the resistivity of forming
contact metal at T > 250 K is linear, since T ≥ TD, where
TD is the Debye temperature, i.e., the metal resistance
increases linearly with the temperature:
2501000 TT , where α is the temperature
coefficient of resistance.
The theoretical curve for the dependence ρс (T) was
calculated using the formula (4). As can be seen from
Fig. 5 (curve 2, line is calculation, points – experiment),
there is a good agreement between the calculated
dependence of the specific contact resistivity ρс with the
experimental data. It is achieved by using the following
parameters: ND1 ≈ 10
9
сm
–2
, r ≈ 6∙10
–8
сm, dD ~ 0.1 μm,
α ≈ 3∙10
–2
K
–1
. Estimation of the dislocation density
obtained from the X-ray diffraction data almost
coincides with the ND1 value calculated using the
formula (4).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 391-395.
doi: 10.15407/spqeo18.04.391
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
395
Attention is drawn to the fact that in this case the α
value is much higher than the temperature coefficient of
resistance growth for pure metals. It may be caused by
the fact that in this case forming contact layer is a
multicomponent alloy.
It has been shown that the ohmic contacts Au–Ti–
Pd–n
+
-InP, formed by successive thermal deposition of
metals in oil-free vacuum onto the n
+
-n-n
++
-n
+++
-InP
substrate heated to 300 °C have linear CVC within the
temperature range 250…380 K. The temperature
dependence ρс in this case is described by the thermal
field emission mechanism. This fact distinguishes the
contact Au–Ti–Pd–n
+
-n-n
++
-n
+++
-InP from the ohmic
contact Au–Ti–Ge–Pd–n
+
-n-n
++
-n
+++
-InP, in which its
advantage, associated with subdoping of the near-contact
area of InP with germanium, offset by the structural
heterogeneity of contact, causing linear increase in ρс
with increasing the temperature.
References
1. H. Eisele, R. Kamua, Submillimeter–Wave InP
Gunn Devices // IEEE Trans. MTT, 52(10),
p. 2371-2378 (2004).
2. H. Eisele, 480 GHz oscillator with an InP Gunn
device // Electron. Lett. 46(6), p. 422-423 (2010).
3. V. Papageorgiou, A. Khalid, C. Li, D.R.S. Cum-
ming, Cofabrication of planar Gunn diode and
HEMT on InP substrate // IEEE Trans. Electron.
Dev. 61(8), p. 2279-2784 (2014).
4. M.I. Maricar, A. Khalid, G. Dunn, D. Cumming,
C.H. Oxley, Experimentally estimated dead space
for GaAs and InP based planar Gunn diodes //
Semicond. Sci. Technol. 30, p. 012001-012005
(2015).
5. N. Braslau, J.B. Gunn, J.L. Staples, Metal-semi-
conductor contact for GaAs bulk effect devices //
Solid–State Electron. 10(5), p. 381-383 (1967).
6. P. Auray, A. Guivarc’h, H.L’Haridon, J.P. Mercier,
Formation, microstructure et resistances des
contacts Au-Ge/n-GaAs, Au-Ge/n-InP, Au-Zn/p-
InP et Au-Be/p-InP // Thin Solid Films, 127(1),
p. 39-68 (1985).
7. R.T. Tung, The physics and chemistry of the
Schottky barrier height // J. Appl. Phys. Rev. 1,
p. 011304-1-01130454 (2014).
8. T. Clausen, O. Leistiko, Metallurgical optimization
for ohmic contacts to InP using conventional
metallization schemes // Microelectron. Eng. 18(4),
p. 305-325 (1992).
9. M.A. Abraham, S-Y. Yu, W.H. Choi, R.T.P. Lee,
S.E. Mohney, Very low resistance alloyed Ni-based
ohmic contacts to InP-capped and uncapped
n
+
In0.53Ga0.47As // J. Appl. Phys. 116(16),
p. 1645061-1645066 (2014).
10. Wu Degi, Ding Wuchang, Yang Shansham, Jia Rui,
Jin Zhi, Liu Xinyi, Optimization of ohmic contact
for InP-based transferred electronic devices // J.
Semiconductors, 35(3), p. 036001-036005 (2014).
11. P. Jian, D.G. Ivey, R. Bruce, G. Knight, Ohmic
contact formation in palladium-based metalli-
zations to n-type InP // J. Electron. Mater. 23(9),
p. 953-962 (1994).
12. P. Maltsev, Yu. Fedorov, R. Galiev, S. Mi-
khailovich, D. Gnatyuk, Millimeter range nitride
devices // Nanoindustry, 3(49), p. 40-51 (2014).
13. A. Dargys, J. Kundrotas, Handbook on Physical
Properties of Ge, Si, GaAs and InP. Sci and
Encyclopedia Publ., Vilnius, 1994.
14. S.J. Pearton, Processing of Wide Band Gap Semi-
conductors: Growth, Processing and Applications.
Noyes Publ. Park Ridge. New Jersey, 2000.
15. A.V. Sachenko, A.E. Belyaev, N.S. Boltovets et al.,
Features of temperature dependence of contact
resistivity in ohmic contacts on lapped n-Si // J.
Appl. Phys. 112(6), p. 063703-0637035 (2012).
16. V.P. Kladko, A.V. Kuchuk, P.M. Lytvyn et al.,
Substrate effects on the strain relaxation in
GaN/AlN short-period superlattices // Nanosc. Res.
Lett. 7(1), p. 289-299 (2012).
17. S.M. Sze, Kwok K. Ng, Physics of Semiconductor
Devices. 3
rd
ed. Wiley, New Jersey, 2007.
18. A.V. Sachenko, A.E. Belyaev, N.S. Boltovets et al.,
Mechanism of contact resistance formation in
ohmic contacts with high dislocation density // J.
Appl. Phys. 111(8), p. 083701-083709 (2012).
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