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

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.

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.

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.

Nanomechanical Effects

2021 ◽  
pp. 253-272
Author(s):  
C. Julian Chen
Keyword(s):  
Barrier Height ◽  
Contact Area ◽  
Soft Materials ◽  
Sample Surface ◽  
Soft Material ◽  
Measurable Effect ◽  
Tunneling Barrier ◽  
Hard Materials ◽  
Small Force ◽  
The Stability

This chapter discusses the effect of force and deformation of the tip apex and the sample surface in the operation and imaging mechanism of STM and AFM. Because the contact area is of atomic dimension, a very small force and deformation would generate a large measurable effect. Three effects are discussed. First is the stability of the STM junction, which depends on the rigidity of the material. For soft materials, hysterisis is more likely. For rigid materials, the approaching and retraction cycles are continuous and reproducible. Second is the effect of force and deformation to the STM imaging mechanism. For soft material such as graphite, force and deformation can amplify the observed corrugation. For hard materials as most metals, force and deformation can decrease the observed corrugation. Finally, the effect of force and deformation on tunneling barrier height measurements is discussed.

Contact area determination in indentation testing of elastomers

2009 ◽  
Vol 24 (3) ◽  
pp. 736-748 ◽  
Author(s):  
Julia K. Deuschle ◽  
H. Matthias Deuschle ◽  
Susan Enders ◽  
Eduard Arzt
Keyword(s):  
Mechanical Properties ◽  
Contact Area ◽  
Indentation Testing ◽  
Dynamic Indentation ◽  
Element Analysis ◽  
Error Sources ◽  
Viscoelastic Effects ◽  
Contact Size ◽  
Area Determination

To evaluate mechanical properties by means of nanoindentation, information on the contact area is crucial. However, the contact area is not directly accessible in experiments and is usually calculated according to the Oliver and Pharr procedure, which turned out to be unsatisfying when applied to viscoelastic materials like polymers. In this study, complementary in situ indentation testing and finite element analysis (FEA) were performed on silicone elastomers. Through this combination of techniques, several individual error sources in the conventional contact area determination have been identified and quantified. For shallow penetrations, contact areas after Oliver and Pharr were up to 40% smaller than the in situ testing results; for larger penetrations, the contact size was overestimated by approximately 6%. The deviations of the resulting mechanical properties were approximately 10%. Viscoelastic effects could be captured if dynamic indentation testing was performed.

Influences of stress on the measurement of mechanical properties using nanoindentation: Part II. Finite element simulations

1996 ◽  
Vol 11 (3) ◽  
pp. 760-768 ◽  
Author(s):  
A. Bolshakov ◽  
W. C. Oliver ◽  
G. M. Pharr
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Contact Area ◽  
Cylindrical Specimen ◽  
Preceding Paper ◽  
Indentation Load ◽  
The Finite Element Method ◽  
Indentation Process ◽  
Plastic Indentation ◽  
Area Determination

The finite element method has been used to study the behavior of aluminum alloy 8009 during elastic-plastic indentation to establish how the indentation process is influenced by applied or residual stress. The study was motivated by the experiments of the preceding paper which show that nanoindentation data analysis procedures underestimate indentation contact areas and therefore overestimate hardness and elastic modulus in stressed specimens. The NIKE2D finite element code was used to simulate indentation contact by a rigid, conical indenter in a cylindrical specimen to which biaxial stresses were applied as boundary conditions. Indentation load-displacement curves were generated and analyzed according to standard methods for determining hardness and elastic modulus. The simulations show that the properties measured in this way are inaccurate because pileup is not accounted for in the contact area determination. When the proper contact area is used, the hardness and elastic modulus are not significantly affected by the applied stress.

Step edge influence on barrier height and contact area in vertical heterojunctions between epitaxial graphene and n-type 4H-SiC

2014 ◽  
Vol 104 (7) ◽  
pp. 073508 ◽  
Author(s):  
M. J. Tadjer ◽  
T. J. Anderson ◽  
R. L. Myers-Ward ◽  
V. D. Wheeler ◽  
L. O. Nyakiti ◽  
...  
Keyword(s):  
Barrier Height ◽  
Contact Area ◽  
Epitaxial Graphene ◽  
Step Edge ◽  
Edge Influence

scholarly journals Низкотемпературные омические контакты на основе Ta/Al к гетероэпитаксиальным структурам AlGaN/GaN на кремниевых подложках

2019 ◽  
Vol 53 (2) ◽  
pp. 249
Author(s):  
Е.В. Ерофеев ◽  
И.В. Федин ◽  
В.В. Федина ◽  
А.П. Фазлеев
Keyword(s):  
Low Temperature ◽  
Surface Morphology ◽  
Contact Resistance ◽  
Contact Area ◽  
Ohmic Contact ◽  
Smooth Surface ◽  
Ohmic Contacts ◽  
Nitrogen Atmosphere ◽  
Silicon Substrates ◽  
20 Nm

AbstractThe formation features of a low-temperature Ta/Al-based ohmic contact to Al_0.25Ga_0.75N/GaN heteroepitaxial structures on silicon substrates are studied. The fabricated ohmic contacts based on Ta/Al/Ti (10/300/20 nm) compositions have a low contact resistance (0.4 Ω mm) and smooth surface morphology of the contact area and its edge after 60-s annealing at T = 550°C in a nitrogen atmosphere.

scholarly journals Новый механизм реализации омических контактов

2018 ◽  
Vol 52 (1) ◽  
pp. 138
Author(s):  
А.В. Саченко ◽  
А.Е. Беляев ◽  
Р.В. Конакова
Keyword(s):  
Barrier Height ◽  
Ohmic Contacts ◽  
Contact Potential Difference ◽  
Surface States ◽  
Semiconductor Interface ◽  
Contact Potential ◽  
Semiconductor Doping ◽  
Semiconductor Contacts ◽  
Contact Barrier ◽  
Semiconductor Contact

AbstractAnalysis of the contact-barrier height taking into account the distribution of surface states along coordinate x perpendicular to the insulator–semiconductor interface is performed for metal–semiconductor contacts with a dielectric gap. It is shown that taking into account the spatial dependence of the density of surface states at rather high semiconductor doping levels leads to a substantial decrease in the barrier height, which promotes the realization of ohmic contacts. It is established that the smaller the metal–semiconductor contact potential difference ϕ_ ms is, the stronger the effect of barrier-height lowering. If ϕ_ ms is negative, this effect can lead to potential sign reversal, i.e., to the realization of an enrichment layer in the space-charge region of the semiconductor even at a high density of surface states. This in turn promotes the manifestation of an anomalous dependence of the contact resistivity on temperature; the resistivity increases with an increase in temperature.

Sign in / Sign up

Export Citation Format

Share Document