Au/Ge/Pd Ohmic Contacts to n-TYPE InP

1992 ◽  
Vol 260 ◽  
Author(s):  
Ping Jian ◽  
Douglas G. Ivey ◽  
Robert Bruce ◽  
Gordon Knight
Keyword(s):  
Thermal Stability ◽  
Contact Resistance ◽  
Transmission Line ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Microstructural Changes ◽  
Ohmic Behavior ◽  
Quaternary Phase ◽  
Transmission Line Method ◽  
Ohmic Contact Formation

ABSTRACTOhmic contact formation and thermal stability in a Au/Ge/Pd metallization to n-type InP, doped to a level of 1017 cm-3, have been investigated. Contact resistance was measured using a transmission line method, while microstructural changes were examined by means of TEM, EDX, CBED and SAD. Contacts became ohmic after annealing at temperatures ranging from 300°C to 375°C. A minimum contact resistance of 2.5×l0-6 Ω-cm2 was obtained after annealing at 350°C for 320s. The drop in resistance to ohmic behavior corresponded to the decomposition of an epitaxial quaternary phase (Au-Ge-Pd-P). Annealing at 400°C and above resulted in Au10In3 spiking into InP and a break down of contact lateral uniformity, which increased contact resistance.

An Approach to Improving the Morphology and Reliability of n-SiC Ohmic Contacts to SiC Using Second-Metal Contacts

2006 ◽  
Vol 527-529 ◽  
pp. 859-862 ◽  
Author(s):  
Matthew H. Ervin ◽  
Kenneth A. Jones ◽  
Un Chul Lee ◽  
Taniya Das ◽  
M.C. Wood
Keyword(s):  
Electrical Properties ◽  
Contact Resistance ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Chemical Properties ◽  
Physical Contact ◽  
Metal Contacts ◽  
Critical Feature ◽  
Excess Carbon ◽  
Ohmic Contact Formation

While nickel ohmic contacts to n-type silicon carbide have good electrical properties, the physical contact, and therefore the reliability, can be poor. An approach is described for using the good electrical properties of Ni ohmic contacts while using another metal for its desired mechanical, thermal and/or chemical properties. In the present work, once the Ni contacts have been annealed forming nickel silicides and achieving low contact resistance, they are etched off. Removing the primary Ni contacts also eliminates the poor morphology, voids, and at least some of the excess carbon produced by the Ni/SiC reaction. The Ni contacts are then replaced by a second contact metal. This second metal displays low contact resistance as-deposited, indicating that the critical feature responsible for the ohmic contact has not been removed by the primary contact etch. Not only does this approach provide more flexibility for optimizing the contact for a given application, it also provides some insight into the ohmic contact formation mechanism.

Pt3In7 Ohmic Contacts to n-TYPE GaAs

1992 ◽  
Vol 260 ◽  
Author(s):  
D. Swenson ◽  
Y. A. Chang
Keyword(s):  
Contact Resistance ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Ohmic Behavior

ABSTRACTA thermodynamic and kinetic rationale was utilized to select Pt3In7 as an ohmic contact to n-GaAs. This analysis predicted that the contact metallurgy would be very simple and extremely uniform upon annealing. Preliminary electrical results showed that annealing samples at temperatures of 650 °C or higher led to ohmic behavior. A contact resistance of 3.4 × 10-5 Ω-cm2 was found upon annealing an uncapped contact at 750 °C for 15 s.

Electrical Modelling and Characterisation of Alloyed Ohmic Contacts

1993 ◽  
Vol 318 ◽  
Author(s):  
Geoffrey K. Reeves ◽  
Patrick W. Leech ◽  
H. Barry Harrison
Keyword(s):  
Contact Resistance ◽  
Transmission Line ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Realistic Model ◽  
Specific Contact Resistance ◽  
Transmission Line Model ◽  
Semiconductor Interface ◽  
Line Model ◽  
Specific Contact

ABSTRACTThis paper briefly reviews the standard Transmission Line Model (TLM) commonly used to measure the specific contact resistance of a planar ohmic contact. It is proposed that in the case of a typical Au-Ge-Ni alloyed ohmic contact, a more realistic model would need to take into account the presence of the alloyed layer at the metal-semiconductor interface. An alternative is described which is based on three contact layers and the two interfaces between them, thus forming a Tri-Layer Transmission Line Model (TLTLM). Expressions are given for the contact resistance Rc and the contact end resistance Re of this structure, together with a current division factor, f. Values for the parameters of this model are inferred from experimentally reported values of Rc and Re for two types of contact.

Ni Graphite Intercalated Compounds in Ohmic Contact Formation on SiC

2006 ◽  
Vol 527-529 ◽  
pp. 863-866
Author(s):  
Wei Jie Lu ◽  
J.A. Michel ◽  
C.M. Lukehart ◽  
W.E. Collins ◽  
W.C. Mitchel
Keyword(s):  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Intercalation Compound ◽  
Carbon Layer ◽  
Atomic Scale ◽  
Contact Formation ◽  
Ohmic Behavior ◽  
Intercalated Compounds ◽  
Ohmic Contact Formation ◽  
Interfacial Carbon

Ohmic contacts on SiC have been investigated extensively in the past decade. However, the mechanism for ohmic contact formation has been a troublesome issue. The interfacial structures at the atomic scale responsible for forming ohmic contacts have not been revealed. Our previous results have shown that carbon can form ohmic contacts on SiC after thermal annealing, and that an interfacial carbon layer between Ni and the SiC improves the contacts significantly. In this study, we have investigated the interactions between Ni and carbon, and ohmic contact formation on SiC using x-ray diffraction (XRD) and Raman spectroscopy. After annealing, ohmic behavior was observed and Ni graphite intercalated compounds (GICs) were found on Ni/C/SiC structures. Unlike conventional graphite intercalated compounds, the Ni atoms substitute for carbon atoms in the graphitic networks in these Ni-GICs. XRD peaks at 21.6° due to the Ni graphitic intercalation compound (Ni-GIC) and at 26.3° due to graphite have been observed. The distance between graphitic sheets is 0.403nm in the Ni graphite intercalated compounds, whereas it is ~20% larger in the graphite. The thickness of the interfacial carbon layer does not affect the formation of Ni-GIC.

Investigation of Aluminum and Titanium/Aluminum Contacts to n-Type Gallium Nitride

1996 ◽  
Vol 449 ◽  
Author(s):  
B. P. Luther ◽  
S. E. Mohney ◽  
T. N. Jackson ◽  
M. Asif Khan ◽  
Q. Chen ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Gallium Nitride ◽  
Contact Resistance ◽  
Ohmic Contact ◽  
Intermetallic Phase ◽  
Native Oxide ◽  
Intimate Contact ◽  
Depth Profiles ◽  
Titanium Aluminum ◽  
Ohmic Contact Formation

ABSTRACTWe report on a study of Al and Ti/Al contacts to n-type GaN. Al contacts on n-GaN (7 x l017cm-3) annealed in forming gas at 600°C reached a minimum contact resistivity of 8x10~6Qcm2 and had much better thermal stability than reported by previous researchers. Ti/Al (35nm/l 15nm) contacts on n-GaN (5xl0I7cm~3) had resistivities of 7 x l0"6Qcm2 and 5xl0"6Qcm2 after annealing in Ar at 400°C for 5min and 600°C for 15sec, respectively. Depth profiles of Ti/Al contacts annealed at 400°C showed that low contact resistance was only achieved after Al diffused to the GaN interface. We propose that the mechanism for ohmic contact formation in Ti/Al contacts annealed in the 400-600°C range includes reduction of the native oxide on GaN by Ti and formation of an Al-Ti intermetallic phase in intimate contact with the GaN. Contacts with different Ti/Al layer thicknesses were investigated and those with 50nm/100nm layers had the same low resistance and better stability than 25nm/125nm contacts.

Microstructural Characterization of Au-Ge-Ni based ohmic contacts to GaAs/AlGaAs modfet device

1987 ◽  
Vol 45 ◽  
pp. 326-327
Author(s):  
A.K. Rai ◽  
A.K. Petford-Long ◽  
A. Ezis ◽  
D.W. Langer
Keyword(s):  
Contact Resistance ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Microstructural Characterization ◽  
Almost Everywhere ◽  
Spacer Layer ◽  
Good Contact ◽  
The Relationship ◽  
Lower Contact

Considerable amount of work has been done in studying the relationship between the contact resistance and the microstructure of the Au-Ge-Ni based ohmic contacts to n-GaAs. It has been found that the lower contact resistivity is due to the presence of Ge rich and Au free regions (good contact area) in contact with GaAs. Thus in order to obtain an ohmic contact with lower contact resistance one should obtain a uniformly alloyed region of good contact areas almost everywhere. This can possibly be accomplished by utilizing various alloying schemes. In this work microstructural characterization, employing TEM techniques, of the sequentially deposited Au-Ge-Ni based ohmic contact to the MODFET device is presented.The substrate used in the present work consists of 1 μm thick buffer layer of GaAs grown on a semi-insulating GaAs substrate followed by a 25 Å spacer layer of undoped AlGaAs.

Ni, NiSi2 and Si Secondary Ohmic Contacts on SiC with High Thermal Stability

2013 ◽  
Vol 740-742 ◽  
pp. 797-800 ◽  
Author(s):  
Stanislav Cichoň ◽  
Petr Macháč ◽  
Jiří Vojtík
Keyword(s):  
Thermal Stability ◽  
Ohmic Contacts ◽  
High Thermal Stability ◽  
Secondary Contact ◽  
High Corrosion Resistance ◽  
Contact Materials ◽  
Adverse Conditions ◽  
Thermal Test ◽  
Ohmic Behavior ◽  
Primary Contact

A method for formation of enhanced ohmic contacts on SiC for operation under adverse conditions has been studied. Ni, NiSi2 and Si ohmic contacts were prepared and tested at 300°C on air for hundreds of hours. NiSi2 and Si showed high thermal stability. Moreover, also the so called secondary contacts showed preserved good electrical and structural properties in the thermal test. The secondary ohmic contacts are formed from original ohmic contacts after they are etched off and replaced with new ones. Secondary ohmic contacts originate in a certain surface modification of the SiC substrate created during high temperature annealing of the original contact. All applied contact materials enable formation of quality secondary contacts which is especially noteworthy at NiSi2 and Si. The results bring new SiC device design perspectives with the application of secondary ohmic contacts. For example, the contact is designed so that the primary contact makes as good ohmic behavior as possible with the secondary contact providing further important contact properties as high corrosion resistance, wire-bonding simplicity etc.

The Development of Solid Phase Regrowth on GaAs and its applications

1993 ◽  
Vol 319 ◽  
Author(s):  
L. C. Wang
Keyword(s):  
Ohmic Contacts ◽  
Solid Phase ◽  
Low Loss ◽  
Ohmic Behavior ◽  
Gaas Substrates ◽  
Layer Structures ◽  
Solid Phase Reactions ◽  
Solid Phase Regrowth ◽  
P Type ◽  
Ohmic Contact Formation

AbstractA solid phase regrowth process on GaAs has been observed in Pd- and Ni- based bi-layer structures, e.g. the Si/Ni, the Ge/Pd, the In/Pd, and the Sb/Pd structures. Due to the regrowth, uniform epitaxial layers of Ge, GaAs, InxGa1-xAs, and GaSbl-xAsx on GaAs substrates by solid phase reactions can achieved. The model of this regrowth process will be presented. Based on this regrowth mechanism, a series of non-spiking planar ohmic contacts on n and p type GaAs have been developed. Low contact resistivity in the range of mid 10−7 Ω-cm2 was obtained. The ohmic contact formation mechanism of these contacts will also be discussed. All the studies suggest that the ohmic behavior is a result of the formation of an n+ or p+ surface layer via solid phase reactions. The regrowth process has also been utilized to achieve compositional disordering of GaAs/AlGaAs superlattices, and low loss AlGaAs/GaAs waveguide has been obtained.

Ohmic Contact Formation to Doped GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
L. L. Smith ◽  
M. D. Bremser ◽  
E. P. Carlson ◽  
T. W. Weeks ◽  
Y. Huang ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Electron Beam Evaporation ◽  
Integrated Analysis ◽  
Cross Sectional ◽  
Contact Materials ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
P Type ◽  
Ohmic Contact Formation ◽  
Contact Resistivities

ABSTRACTOhmic contact strategies for n- and p-type GaN have been investigated electrically, chemically, and microstructurally using transmission line measurements, high-resolution EELS and cross-sectional TEM, respectively. The contributions to contact performance from work function differences, carrier concentrations, annealing treatments, and interface metallurgy have been examined. The contact materials of Ti, TiN, Au, and Au/Mg were deposited via electron beam evaporation; Al was deposited via thermal evaporation. As-deposited Al and TiN contacts to highly doped n-GaN were ohmic, with room-temperature specific contact resistivities of 8.6×10−5 Ω cm2 and 2.5×10−5 Ωcm2 respectively. The Ti contacts developed low-resistivity ohmic behavior as a result of annealing; TiN contacts also improved with further heat treatment. For p-GaN, Au became ohmic with annealing, while Au/Mg contacts were ohmic in the as-deposited condition. The performance, structure, and composition of different contact schemes varied widely from system to system. An integrated analysis of the results of this study is presented below and coupled with a discussion of the most appropriate contact systems for both n- and p-type GaN.

Ohmic Contact Formation Mechanism of Pd-based Contact to p-GaN

2000 ◽  
Vol 622 ◽  
Author(s):  
Dae-Woo Kim ◽  
Joon Cheol Bae ◽  
Woo Jin Kim ◽  
Hong Koo Baik ◽  
Chong Cook Kim ◽  
...  
Keyword(s):  
Schottky Barrier ◽  
Barrier Height ◽  
Formation Mechanism ◽  
Ohmic Contact ◽  
Room Temperature ◽  
Schottky Barrier Height ◽  
Contact Formation ◽  
Ohmic Behavior ◽  
Plane Direction ◽  
Ohmic Contact Formation

ABSTRACTWe have investigated surface treatment effect on the interfacial reaction of Pd/p-GaN interface and also room temperature ohmic contact formation mechanism of Pd-based ohmic contact. In order to examine room temperature ohmic behavior, various metal contact systems were deposited and current-voltage measurements were carried out. In spite of large theoretical Schottky barrier height between Pd and p-GaN, Pd-based contact showed perfect ohmic characteristic even before annealing. According to the results of synchrotron X-ray radiation, the closed-packed atomic planes (111) of the Pd film were quite well ordered in surface normal direction as well as in the in-plane direction. The effective Schottky barrier height of Au/Pd/Mg/Pd/p-GaN was 0.47eV, which was estimated by Norde method. This discrepancy between theoretical barrier height and the measured one might be due to the epitaxial growth of Pd contact metal and so the room-temperature ohmic characteristic of Pd-based ohmic contact was related strongly to the in-plane epitaxial quality of metal on p-GaN.

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