Formation and Characterization of Ohmic Contacts on Diamond

1992 ◽  
Vol 270 ◽  
Author(s):  
V. Venkatesan ◽  
D.M. Malta ◽  
K. Das
Keyword(s):  
Ion Implantation ◽  
Contact Resistance ◽  
Ohmic Contacts ◽  
Chemical Vapor ◽  
Polycrystalline Diamond ◽  
Temperature Cycling ◽  
Specific Contact Resistance ◽  
Naturally Occurring ◽  
Specific Contact

ABSTRACTLow resistance ohmic contacts have been fabricated on a naturally occurring lib diamond crystal and on polycrystalline diamond films by B ion-implantation and subsequent Ti/Au bilayer metallization. A high B concentration was obtained at the surface by ion implantation, a postimplant anneal and a subsequent chemical removal of the graphite layer. A bilayer metallization of Ti followed by Au, annealed at 850°C, yielded specific contact resistance values (as measured using a standard transmission line model (TLM) pattern) of the order of 10-5 Ω cm2 for chemical vapor deposition (CVD) grown polycrystalline films and the natural lib crystal. Specific contact resistance values have also been determined from circular TLM measurements on CVD films and the values compared to those from standard TLM measurements. These contacts were stable to a measurement temperature of ∼400°C and no degradation due to temperature cycling was observed.

Formation of Ni/Pt/Au Ohmic Contacts to p-GaN

1997 ◽  
Vol 482 ◽  
Author(s):  
Ja-Soon Jang ◽  
Hyo-Gun Kim ◽  
Kyung-Hyun Park ◽  
Chang-Sub Um ◽  
Il-Ki Han ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Chemical Vapor ◽  
Electron Beam Evaporation ◽  
Specific Contact Resistance ◽  
Metal Thin Films ◽  
Linear Behavior ◽  
Specific Contact ◽  
P Type

AbstractWe report a new Ni/Pt/Au (20/30/80 nm) metallization scheme to achieve a low ohmic contacts to p-type GaN with a carrier concentration of 9.4 × 1016 cm-3. A Mg-doped GaN layer (0.5 μm) was grown on (0001) sapphire substrate by metalorganic chemical vapor deposition (MOCVD). All metal thin films were deposited on the p-GaN layer in an electron-beam evaporation system. Samples were annealed by a rapid thermal annealing (RTA) process at a range of temperatures from 300 °C to 850 °C under a flowing Ar atmosphere. A circulartransmission line model (c-TLM) was employed to calculate the specific contact resistance, and current-voltage (I-V) data were measured with HP4155A. The Ni/Pt/Au contacts without the annealing process showed nearly rectifying characteristics. The ohmic contacts were formed on the samples annealed at 500 °C for 30 sec and the I-V data showed a linear behavior. The specific contact resistance was 2.1 × 10-2 Ωcm2. However with increasing the annealing temperature above 600 °C, ohmic contacts were again degraded. Auger electron spectroscopy (AES) depth profiles were used to investigate the interfacial reactions between the trilayer and GaN. AES results suggested that Pt plays a significant role in forming ohmic contact as an acceptor at the interface. Atomic force microscope (AFM) also showed that the samples with good ohmic contact have very smooth surface.

Improvement of the Specific Contact Resistance on P-Type 4H-SiC by Using a Highly P-Typed Doped 4H-SiC Layer Selectively Grown by VLS Transport

2014 ◽  
Vol 806 ◽  
pp. 57-60
Author(s):  
Nicolas Thierry-Jebali ◽  
Arthur Vo-Ha ◽  
Davy Carole ◽  
Mihai Lazar ◽  
Gabriel Ferro ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Schottky Barrier Height ◽  
Annealing Temperature ◽  
Process Condition ◽  
Specific Contact Resistance ◽  
High Doping Level ◽  
Annealing Temperatures ◽  
Specific Contact ◽  
P Type

This work reports on the improvement of ohmic contacts made on heavily p-type doped 4H-SiC epitaxial layer selectively grown by Vapor-Liquid-Solid (VLS) transport. Even before any annealing process, the contact is ohmic. This behavior can be explained by the high doping level of the VLS layer (Al concentration > 1020 cm-3) as characterized by SIMS profiling. Upon variation of annealing temperatures, a minimum value of the Specific Contact Resistance (SCR) down to 1.3x10-6 Ω.cm2 has been obtained for both 500 °C and 800 °C annealing temperature. However, a large variation of the SCR was observed for a same process condition. This variation is mainly attributed to a variation of the Schottky Barrier Height.

Current Transport in Ti/Al/Ni/Au Ohmic Contacts to GaN and AlGaN

2007 ◽  
Vol 556-557 ◽  
pp. 1027-1030 ◽  
Author(s):  
Ferdinando Iucolano ◽  
Fabrizio Roccaforte ◽  
Filippo Giannazzo ◽  
A. Alberti ◽  
Vito Raineri
Keyword(s):  
Contact Resistance ◽  
Field Emission ◽  
Ohmic Contacts ◽  
Theoretical Models ◽  
Specific Contact Resistance ◽  
Strong Increase ◽  
Current Transport ◽  
Electrical Characteristics ◽  
Structural And Electrical Properties ◽  
Specific Contact

In this work, the structural and electrical properties of Ti/Al/Ni/Au contacts on n-type Gallium Nitride were studied. An ohmic behaviour was observed after annealing above 700°C. The structural analysis showed the formation of an interfacial TiN layer and different phases in the reacted layer (AlNi, AlAu4, Al2Au) upon annealing. The temperature dependence of the specific contact resistance demonstrated that the current transport occurs through thermoionic field emission in the contacts annealed at 600°C, and field emission after annealing at higher temperatures. By fitting the data with theoretical models, a reduction of the Schottky barrier from 1.21eV after annealing at 600°C to 0.81eV at 800°C was demonstrated, together with a strong increase of the carrier concentration at the interface. The reduction of the contact resistance upon annealing was discussed by correlating the structural and electrical characteristics of the contacts.

Modelling Geometrical Effects of Parasitic and Contact Resistance of FET Devices

1996 ◽  
Vol 427 ◽  
Author(s):  
Geoffrey K. Reeves ◽  
H. Barry Harrison ◽  
Patrick W. Leech
Keyword(s):  
Contact Resistance ◽  
Material Properties ◽  
Ohmic Contacts ◽  
Difficult Problem ◽  
Specific Contact Resistance ◽  
Metal Silicide ◽  
Transmission Line Model ◽  
Specific Contact ◽  
Geometrical Effects ◽  
Contact Parameters

AbstractThe continual trend in decreasing the dimensions of semiconductor devices results in a number of technological problems. One of the more significant of these is the increase in contact resistance, Rc. In order to understand and counteract this increase, Rc needs to be quantitatively modelled as a function of the geometrical and material properties of the contact. However the use of multiple semiconductor layers for ohmic contacts makes the modelling and calculation of Rc a more difficult problem. In this paper, a Tri-Layer Transmission Line Model (TLTLM) is used to analyse a MOSFET ohmic contact and gatedrain region. A quantitative assessment of the influence on Rc of important contact parameters such as the metal-silicide specific contact resistance, the silicide-silicon specific contact resistance and the gate-drain length can thus be made. The paper further describes some of the problems that may be encountered in defining Rc when the dimensions of certain types of contact found in planar devices decrease.

Ohmic Contacts to p-Type InGaAs/InP with a Graded Bandgap Heterobarrier

1993 ◽  
Vol 318 ◽  
Author(s):  
Patrick W. Leech ◽  
Geoffrey K. Reeves
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Rutherford Backscattering Spectrometry ◽  
Specific Contact Resistance ◽  
Superlattice Structure ◽  
Specific Contact ◽  
P Type ◽  
Metal Layers ◽  
Anneal Temperature ◽  
Graded Bandgap

ABSTRACTOhmic contacts to p-type InP with an In0.47Ga0.53As buffer layer and an interposed superlattice of 50 Å In0.47Ga0.53As/ 50 Å InP have been investigated. Initial studies of contacts to In0.47Ga0.53As/ InP without the superlattice structure have shown that Pd/Zn/Pd/Au metallization produced a lower specific contact resistance (pc = 1.1 × 10−4 Ω cm2) than Pd/Ge/Au, and over a wider range of anneal temperature than Au/Zn/Au. The incorporation of the superlattice in the p-In0.47Ga0.53As/ InP structure resulted in Pd/Zn/Pd/Au contacts with pc of 3.2 × 10−5 Ω cm2 as-deposited and 7.5 × 10−6 Ω.cm2 after a 500 °C anneal. The presence of Pd/Zn in the metallization was shown as important in reducing pc. Significant intermixing of the metal layers and In0.47Ga0.53As occured at ≥ 350 °C, as revealed by Rutherford backscattering spectrometry.

Ni-Al-Ti Ohmic Contacts with Preserved Form Factor and Few 10- 4 Ωcm2 Specific Resistance on 0.1-1 Ωcm p-Type 4H-SiC

2018 ◽  
Vol 924 ◽  
pp. 385-388 ◽  
Author(s):  
Roberta Nipoti ◽  
Maurizio Puzzanghera ◽  
Maria Concetta Canino ◽  
Giovanna Sozzi ◽  
Paolo Fedeli
Keyword(s):  
Form Factor ◽  
Contact Resistance ◽  
Contact Area ◽  
Room Temperature ◽  
Ohmic Contacts ◽  
Specific Resistance ◽  
Thickness Ratio ◽  
Specific Contact Resistance ◽  
Specific Contact ◽  
P Type

This study shows that a thin Ni film on Al/Ti/4H-SiC metal pads allows to preserve the pad form factor during a 1000 °C/2 min treatment, provided that the Al and Ti film thicknesses are sufficiently thin. Moreover, by reducing the Al to Ti thickness ratio, droplet formation in the contact area is avoided and a mirror-like appearance is obtained. This optimal contact morphology corresponds to a specific contact resistance of few 10-4Ωcm2at room temperature on p-type 4H-SiC with resistivity in the range 0.1 – 1 Ωcm.

Influence of Ni and Nb thickness on low specific contact resistance and high-temperature reliability of ohmic contacts to 4H-SiC

2019 ◽  
Vol 58 (11) ◽  
pp. 116501 ◽  
Author(s):  
Vuong Van Cuong ◽  
Seiji Ishikawa ◽  
Tomonori Maeda ◽  
Hiroshi Sezaki ◽  
Satoshi Yasuno ◽  
...  
Keyword(s):  
High Temperature ◽  
Contact Resistance ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Specific Contact

Current Transport Mechanisms in Au-Free Metallizations for CMOS Compatible GaN HEMT Technology

2020 ◽  
Vol 1004 ◽  
pp. 725-730
Author(s):  
Fabrizio Roccaforte ◽  
Monia Spera ◽  
Salvatore Di Franco ◽  
Raffaella Lo Nigro ◽  
Patrick Fiorenza ◽  
...  
Keyword(s):  
Barrier Height ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Current Transport ◽  
Large Area ◽  
Si Substrates ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Thermionic Field Emission

Gallium nitride (GaN) and its AlGaN/GaN heterostructures grown on large area Si substrates are promising systems to fabricate power devices inside the existing Si CMOS lines. For this purpose, however, Au-free metallizations are required to avoid cross contaminations. In this paper, the mechanisms of current transport in Au-free metallization on AlGaN/GaN heterostructures are studied, with a focus on non-recessed Ti/Al/Ti Ohmic contacts. In particular, an Ohmic behavior of Ti/Al/Ti stacks was observed after an annealing at moderate temperature (600°C). The values of the specific contact resistance ρc decreased from 1.6×104 Ω.cm2 to 7×105 Ω.cm2 with increasing the annealing time from 60 to 180s. The temperature dependence of ρc indicated that the current flow is ruled by a thermionic field emission (TFE) mechanism, with barrier height values of 0.58 eV and 0.52 eV, respectively. Finally, preliminary results on the forward and reverse bias characterization of Au-free tungsten carbide (WC) Schottky contacts are presented. This contact exhibited a barrier height value of 0.82 eV.

Al/Ni And Al/Ti Ohmic Contact To P-type SiC Diffused Layer

2000 ◽  
Vol 640 ◽  
Author(s):  
Xaiobin Wang ◽  
Stanislav Soloviev ◽  
Ying Gao ◽  
G. Straty ◽  
Tangali Sudarshan ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Metal Contacts ◽  
Transfer Length ◽  
Type Layer ◽  
Transmission Line Method ◽  
Specific Contact ◽  
Background Doping ◽  
P Type

ABSTRACTOhmic contacts to p-type SiC were fabricated by depositing Al/Ni and Al/Ti followed by high temperature annealing. A p-type layer was fabricated by Al or B diffusion from vapor phase into both p-type and n-type substrates. The thickness of the diffused layer was about 0.1–0.2 μm with surface carrier concentration of about 1.0×1019cm−3. Metal contacts to a p-type substrate with a background doping concentration of 1.2×1018cm−3, without a diffusion layer, were also formed. The values of specific contact resistance obtained by Circular Transmission Line Method (CTLM) and Transfer Length Method (TLM) for the n-type substrate, and by Cox & Strack method for p-type substrate, respectively, varied from 1.3×10−4Ωcm2 to 8.8×10−3 Ωcm2. The results indicate that the specific contact resistance could be significantly reduced by creating a highly doped diffused surface layer.

Sign in / Sign up

Export Citation Format

Share Document