TEM assessment of GaN/AlGaN/TiAlTiAu and GaN/AlGaN/TiAlPdAu ohmic contacts

AbstractTiAlTiAu and TiAlPdAu contacts to GaN/AlGaN, rapid thermal annealed at temperatures ranging from 650°C to 950°C, have been investigated using conventional and chemical TEM analysis. Ohmic behaviour was seen for TiAlTiAu contacts annealed at 750°C or higher, but was not observed in TiAlPdAu contacts annealed at up to 950°C. The effect of annealing temperature on the structural evolution of the contact is explained in terms of different extents of interfacial reaction. In particular, the formation of TiN after anneals at high temperatures is required to activate the contact. At anneals of 950°C, TiAlTiAu samples show a structure of TiN grains within an interfacial band, with TiN inclusions into the AlGaN preceded by an Al-Au diffusion front. Inclusion formation and the effect on the contact electrical performance is described.

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Structural Analysis of Au/Ti/Al/SiC Contacts in Dependence on the Initial Composition and Annealing

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.12.55 ◽

2010 ◽

Vol 12 ◽

pp. 55-63 ◽

Cited By ~ 1

Author(s):

Lilyana Kolaklieva ◽

Roumen Kakanakov ◽

Maya Marinova ◽

Efstathios K. Polychroniadis

Keyword(s):

Carrier Transport ◽

Ohmic Contacts ◽

Annealing Temperature ◽

Strong Dependence ◽

Initial Contact ◽

Initial Composition ◽

Tem Analysis ◽

Optimal Annealing Temperature ◽

Two Phases ◽

P Type

The dependence of the structure and composition of nanolayered Au/Ti/Al ohmic contacts to p-type 4H-SiC on the initial Ti:Al ratio has been investigated. Two contact compositions, Au/Ti(70%)/Al(30%) and Au/Ti(30%)/Al(70%), have been studied regarding the electrical properties, structure, composition and annealing temperature in the interval 850 – 1000o C. The correlation between the electrical behaviour and structure of the annealed contacts is discussed. Very low resistivity of 1.42x10-5 .cm2 after annealing at 900o C has been obtained for the contact having an initial composition Ti:Al (30:70), while the lowest resistivity of 1.21x10-5 .cm2 has been measured for the contact with a composition Ti:Al (70:30) after annealing at 1000o C. Strong dependence of the contact structure on the Ti:Al ratio and annealing temperature, respectively, has been found out. A presence of two phases, Au2Ti and Al3Ti, in all contacts has been determined after annealing, despite the temperature value and Ti:Al ratio. The TEM analysis reveals that titanium and aluminum silicides and carbides are formed after annealing as the Ti:Al ratio affects the kind of silicides and carbides created. It is obtained that the initial composition of the deposited metal layers influences only the phase composition of the annealed contact but not the grain sizes of the dominant phases formed. The origin of the ohmic properties improvement is explained by the formation of Ti3SiC2 compound and/or enhanced carrier transport by the presence of metal spikes into SiC depending on the initial contact composition and as consequence the optimal annealing temperature.

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Oxidation Behavior and Structural Transformation of (CrTaTiVZr)N Coatings

Coatings ◽

10.3390/coatings10040415 ◽

2020 ◽

Vol 10 (4) ◽

pp. 415

Author(s):

Zue-Chin Chang ◽

Jun-Yang Liang

Keyword(s):

Annealing Temperature ◽

Structural Evolution ◽

Oxide Phase ◽

Electrical Performance ◽

Solid Solution Phase ◽

Face Centered Cubic ◽

Rutile Tio2 ◽

Si Substrates ◽

Annealing Temperatures ◽

Tio2 Phase

(CrTaTiVZr)N coatings were prepared on Si substrates through the reactive magnetron sputtering system to investigate the oxidation behaviors and structural evolution of the coatings at different annealing temperatures in air. The (CrTaTiVZr)N coating had a face-centered cubic structure with an oxidation temperature of up to 300 °C, but its surface changed into the amorphous oxide phase and then into the rutile TiO2 phase when the annealing temperature was increased to 500 °C. The rutile TiO2 phase continued to grow, and an additional solid solution phase of body-centered tetragonal I41/amd was formed at annealing temperatures beyond 600 °C. The high annealing temperature promoted the oxidation to progress along the thickness direction and synergistically developed the porosity. As a result, the hardness and the electrical performance of the coating deteriorated. The hardness decreased from 34.30 GPa to 1.52 GPa, and the electrical resistivity increased from 142 µΩ·cm to 17.5 Ω·cm.

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Nano-Electro-Structural Evolution of Ni-Si Ohmic Contacts to 3C-SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.615-617.569 ◽

2009 ◽

Vol 615-617 ◽

pp. 569-572

Author(s):

Jens Eriksson ◽

Fabrizio Roccaforte ◽

Filippo Giannazzo ◽

Raffaella Lo Nigro ◽

Giuseppe Moschetti ◽

...

Keyword(s):

Ohmic Contacts ◽

Annealing Temperature ◽

Structural Evolution ◽

Electrical Characterization ◽

Nickel Silicide ◽

Specific Contact Resistance ◽

Specific Contact ◽

Nanoscale Measurements

This paper reports on the macro- and nanoscale electro-structural evolution, as a function of annealing temperature, of nickel-silicide Ohmic contacts to 3C-SiC, grown on 6H-SiC substrates by a Vapor-Liquid-Solid (VLS) technique. The structural and electrical characterization of the contacts, carried out by combining different techniques, showed a correlation between the annealing temperature and the electrical characteristics in both the macro- and the nanoscale measurements. Increasing the annealing temperature between 600 and 950 °C caused a gradual increase of the uniformity of the nanoscale current-distribution, with an accompanying reduction of the specific contact resistance from 5 x 10-5 to 8.4 x 10-6 Ωcm2. After high temperature annealing (950 °C) the structural composition of the contacts stabilized, as only the Ni2Si phase was detected. A comparison with previous literature findings suggests a superior crystalline quality of the single domain VLS 3C-SiC layers.

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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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.806.57 ◽

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.

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Structural Evolution of Corundum at High Temperatures

Japanese Journal of Applied Physics ◽

10.1143/jjap.47.616 ◽

2008 ◽

Vol 47 (1) ◽

pp. 616-619 ◽

Cited By ~ 22

Author(s):

Saki Kondo ◽

Kenji Tateishi ◽

Nobuo Ishizawa

Keyword(s):

High Temperatures ◽

Structural Evolution

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Effects of implantation energy and annealing temperature on the structural evolution of Ge+-implanted amorphous Si

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms ◽

10.1016/j.nimb.2005.05.034 ◽

2005 ◽

Vol 237 (1-2) ◽

pp. 384-389 ◽

Cited By ~ 2

Author(s):

J.H. He ◽

H.H. Lin ◽

W.W. Wu ◽

L.J. Chen

Keyword(s):

Annealing Temperature ◽

Structural Evolution ◽

Implantation Energy ◽

Amorphous Si

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Nonalloyed ohmic contacts in AlGaN/GaN HEMTs by ion implantation with reduced activation annealing temperature

IEEE Electron Device Letters ◽

10.1109/led.2006.870419 ◽

2006 ◽

Vol 27 (4) ◽

pp. 205-207 ◽

Cited By ~ 55

Author(s):

F. Recht ◽

L. McCarthy ◽

S. Rajan ◽

A. Chakraborty ◽

C. Poblenz ◽

...

Keyword(s):

Ion Implantation ◽

Ohmic Contacts ◽

Annealing Temperature ◽

Gan Hemts ◽

Activation Annealing

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Characteristics and aging of SiC MOSFETs operated at very high temperatures

MRS Proceedings ◽

10.1557/opl.2014.581 ◽

2014 ◽

Vol 1693 ◽

Cited By ~ 2

Author(s):

Dean P. Hamilton ◽

Michael R. Jennings ◽

Craig A. Fisher ◽

Yogesh K. Sharma ◽

Stephen J. York ◽

...

Keyword(s):

High Temperature ◽

High Temperatures ◽

Threshold Voltage ◽

Thermal Aging ◽

Ohmic Contacts ◽

Stress Tests ◽

Temperature Capability ◽

Temperature Constant ◽

Voltage Management ◽

Very High

ABSTRACTSilicon carbide power devices are purported to be capable of operating at very high temperatures. Current commercially available SiC MOSFETs from a number of manufacturers have been evaluated to understand and quantify the aging processes and temperature dependencies that occur when operated up to 350°C. High temperature constant positive bias stress tests demonstrated a two times increase in threshold voltage from the original value for some device types, which was maintained indefinitely but could be corrected with a long negative gate bias. The threshold voltages were found to decrease close to zero and the on-state resistances increased quite linearly to approximately five or six times their room temperature values. Long term thermal aging of the dies appears to demonstrate possible degradation of the ohmic contacts. This appears as a rectifying response in the I-V curves at low drain-source bias. The high temperature capability of the latest generations of these devices has been proven independently; provided that threshold voltage management is implemented, the devices are capable of being operated and are free from the effects of thermal aging for at least 70 hours cumulative at 300°C.

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