Metal Contacts to n- AlXGa1-xN

1997 ◽  
Vol 482 ◽  
Author(s):  
A. Sampath ◽  
H. M. Ng ◽  
D. Korakakis ◽  
T. D. Moustakas
Keyword(s):  
Barrier Height ◽  
Conduction Band ◽  
Ohmic Contacts ◽  
Schottky Barriers ◽  
Metal Contacts ◽  
Vacuum Level ◽  
Al Content ◽  
Sequential Deposition ◽  
Contact Resistivities

AbstractIn this paper we report on the formation of ohmic contacts to n- AlxGa1-xN alloys. The films were produced by plasma-assisted MBE and doped n- type with silicon at doping levels between 1018 to 1019 cm-3. Contacts were formed by sequential deposition of 200 Å of Ti and 2000 Å of Al and the contact resistivities were determined from TLM measurements. For low Al- content (x<. 10) the I-V characteristics are linear with contact resistivities of between 10-4 to 10-5 cm2. The contacts become progressively non-ohmic at Al concentrations greater than 10%. There results are consistent with the Schottky limit being applicable to these alloys and thus the Ti/Al contact forms Schottky barriers with higher barrier height as the conduction band of the alloy moves towards the vacuum level.

Metal - Gan Contact Technology

1998 ◽  
Vol 514 ◽  
Author(s):  
S. S. Lau
Keyword(s):  
Barrier Height ◽  
Carrier Transport ◽  
Ohmic Contacts ◽  
Accurate Determination ◽  
Surface Cleaning ◽  
Metal Contacts ◽  
Metal Thin Films ◽  
Ohmic Behavior ◽  
Metal Silicides

ABSTRACTIn this talk, we summarize the experimental results obtained on metal-GaN interactions in our laboratory. These interactions include the epitaxial growth of metal thin films on chemically cleaned GaN surfaces, metal silicides for Schottky contacts and metallization schemes for ohmic contacts. We found that many fcc and hcp metals can grow epitaxially on (0001) GaN surfaces at room temperature without in-situ surface cleaning. Metal silicide contacts (such as PtSi) may be more suitable for high temperature applications than elemental contacts, due to the thermal stability of silicides. The intrinsic mechanisms for ohmic behavior for various metal contacts are not well understood at present. More consistent barrier height values measured experimentally can shed light on this issue. Due to the defective nature of the GaN layers, carrier transport across the metal/GaN interface can be due to a number of transport mechanisms, thus making accurate determination of the barrier height difficult. In spite of these difficulties, it seems possible to draw certain general conclusions on the electrical behavior of metal contacts on n-GaN.

A Proposed Regrowth Mechanism for the Enhancement of Schottky Barrier Height to N-GAAS

1994 ◽  
Vol 337 ◽  
Author(s):  
C-P. Chen ◽  
Y. A. Chang ◽  
T.F. Kuech
Keyword(s):  
Schottky Barrier ◽  
Barrier Height ◽  
Schottky Barrier Height ◽  
Gaas Layer ◽  
Dark Field ◽  
Schottky Barriers ◽  
Semiconductor Interface ◽  
Al Content ◽  
Current Voltage ◽  
High Al Content

ABSTRACTA systematic study of the enhancement of Schottky barriers to n-GaAs diodes has been carried out using the Ni-Al binary system. The diodes, Ni2Al3/n-GaAs, Ni2Al3/Ni/n-GaAs, Ni/Al/Ni/n-GaAs and NiAl/Al/Ni/n-GaAs, have been realized by sputter deposition at a base pressure ∼2xl0-7 Torr. A high Schottky barrier height ranging from 0.95 to 0.98 eV (deduced from current-voltage measurements) was observed for all the annealed contacts except for Ni2Al3/n-GaAs contacts. The enhancement of the Schottky barrier height in all the contacts was attributed to the formation of a high Al content (Al,Ga)As layer at the metal/semiconductor interface. The formation of this (Al,Ga)As layer was explained in terms of a regrowth mechanism. In this mechanism, Ni reacts with GaAs initially at low temperatures, forming NixGaAs. The NixGaAs layer is believed to react with the Ni-Al layer to form the (Al,Ga)As layer when subjected to a high temperature annealing. A (200) dark field XTEM image of the annealed contact was used to demonstrate the existence of this (Al,Ga)As phase.

TEM Observations of Ti/AlNi/Au Contacts on p-Type 4H-SiC

2010 ◽  
Vol 645-648 ◽  
pp. 729-732 ◽  
Author(s):  
Bang Hung Tsao ◽  
Jacob W. Lawson ◽  
James D. Scofield ◽  
Javier Francisco Baca
Keyword(s):  
Barrier Height ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Low Energy ◽  
Interfacial Structure ◽  
Cross Sectional ◽  
Composite Configuration ◽  
P Type ◽  
Contact Resistivities ◽  
Anneal Temperature

Improved AlNi-based ohmic contacts to p-type 4H-SiC have been achieved using low energy ion (Al+)implantation, the addition of a thin Ti layer, and a novel two-step implant activation anneal process. AlNi/Au contacts with and without Ti were studied, which resulted in contact resistivities around 1.8x10-4 -cm2 and 2.0x10-3 -cm2 respectively. Even though these values were higher than those of the Ti/AlNi/W system, which was the focus of previous studies, the reduced anneal temperature (650 to 700°C) implies that Ti/AlNi/Au is a promising composite configuration. Cross-sectional TEM and EDX were used to investigate the interfacial structure of the contacts. One possible mechanism for the improved ohmic contact behavior is that the addition of Au and Ti resulted in a reduction barrier height.

Contacting Diffusion with FIB for Backside Circuit Edit—Procedures and Material Analysis

2005 ◽  
Author(s):  
U. Kerst ◽  
P. Sadewater ◽  
R. Schlangen ◽  
C. Boit ◽  
R. Leihkauf ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Electrical Properties ◽  
Process Parameters ◽  
Thermal Effects ◽  
Silicon Surface ◽  
Ohmic Contacts ◽  
Ion Beam ◽  
Schottky Barriers ◽  
Material Analysis ◽  
Type Silicon

Abstract The feasibility of low-ohmic FIB contacts to silicon with a localized silicidation was presented at ISTFA 2004 [1]. We have systematically explored options in contacting diffusions with FIB metal depositions directly. A demonstration of a 200nm x 200nm contact on source/drain diffusion level is given. The remaining article focuses on the properties of FIB deposited contacts on differently doped n-type Silicon. After the ion beam assisted platinum deposition a silicide was formed using a forming current in two configurations. The electrical properties of the contacts are compared to furnace anneal standards. Parameters of Schottky-barriers and thermal effects of the formation current are studied with numerical simulation. TEM images and material analysis of the low ohmic contacts show a Pt-silicide formed on a silicon surface with no visible defects. The findings indicate which process parameters need a more detailed investigation in order to establish values for a practical process.

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.

Inhomogeneous ohmic contacts: Barrier height and contact area determination

2012 ◽  
Vol 101 (5) ◽  
pp. 051604 ◽  
Author(s):  
Yang Li ◽  
Wei Long ◽  
Raymond T. Tung
Keyword(s):  
Barrier Height ◽  
Contact Area ◽  
Ohmic Contacts ◽  
Area Determination

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.

Evidence for Fermi-energy pinning relative to either valence or conduction band in Schottky barriers

1989 ◽  
Vol 40 (15) ◽  
pp. 10607-10610 ◽  
Author(s):  
J. Y. Duboz ◽  
P. A. Badoz ◽  
F. Arnaud d’Avitaya ◽  
E. Rosencher
Keyword(s):  
Conduction Band ◽  
Fermi Energy ◽  
Schottky Barriers

Improved Ohmic Contacts to n-Type GaAs, Using Oiboride Diffusion Barriers

1985 ◽  
Vol 54 ◽  
Author(s):  
Joel R. Shappirio ◽  
Robert A. Lux ◽  
John J. Finnegan ◽  
Donald C. Fox ◽  
Joseph H. Kwiatkowski
Keyword(s):  
Diffusion Barrier ◽  
Ohmic Contacts ◽  
Diffusion Barriers ◽  
Specific Contact ◽  
Contact Resistivities

ABSTRACTOhmic contacts employing Au/Metal/Au/Ge/Ni (Metal=Ni or. TiB2) to n-type GaAs have been investigated. Alloying of the contacts, performed by both optical (rapid thermal) and strip heater methods, resulted in very low specific contact resistivities for the samples employing the TiB2 diffusion barrier. Such contacts are shown to be stable on aging at 350C for 180 hours.

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