The Materials Properties of a Nickel Based Composite Contact to n-Sic for Pulsed Power Switching

2000 ◽  
Vol 622 ◽  
Author(s):  
M. W. Cole ◽  
P. C. Joshi ◽  
F. Ren ◽  
C. W. Hubbard ◽  
M. C. Wood ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Pulsed Power ◽  
Power Switching ◽  
Semiconductor Interface ◽  
Carbide Phases ◽  
Annealing Temperatures ◽  
Ohmic Behavior ◽  
Reaction Region ◽  
Composite Contact ◽  
Surface Morphologies

ABSTRACTNovel Ni/WSi/Ti/Pt composite Ohmic contacts to n-SiC were investigated as a function of annealing temperatures up to 1000°C. The onset of Ohmic behavior occurred at annealing temperatures of 900°C. Annealing at temperatures between 950°and 1000°C yielded excellent Ohmic behavior. At these temperatures the contact-SiC interface was smooth, defect free and characterized by a narrow Ni2Si reaction region. The annealed contacts possessed atomically smooth surface morphologies and exhibited minimal contact expansion. The residual carbon, resultant from SiC decomposition, was constrained by reaction with the WSi and Ti metallization layers forming carbide phases of W and Ti. The locations of the carbide phases were spatially distant from the metal semiconductor interface. Our results demonstrate that the Ni/WSi/Ti/Pt composite Ohmic contact maintains the desirable electrical properties associated with Ni contacts and possess excellent interfacial, compositional and surface properties which are required for reliable high power and high temperature device operation.

A Two-Step Process for the Formation of Au-Ge Ohmic Contacts to n-GaAs

1990 ◽  
Vol 181 ◽  
Author(s):  
M. A. Dornath-Mohr ◽  
M. W. Cole ◽  
H. S. Lee ◽  
C. S. Wrenn ◽  
D. W. Eckart ◽  
...  
Keyword(s):  
Low Temperature ◽  
Barrier Height ◽  
Gaas Substrate ◽  
Ohmic Contacts ◽  
Atomic Percent ◽  
Second Step ◽  
Semiconductor Interface ◽  
Step Process ◽  
Ohmic Behavior

ABSTRACTThe formation of low temperature Au-Ge contacts to n-GaAs is a two-step process. In the first step, the metals segregate into Au and Ge rich regions and the intermixing of the Au and Ge with the Ga and As causes a reduction in the barrier height. The second step occurs after extended annealing, during which time Au and Ge continue to diffuse into the substrate. An orthorhombic Au-Ga phase is formed and it is likely that other Au-Ga or Ge-As phases are formed. The length of the extended anneal is dependent upon the atomic percent of Ge in the film, with the 10 at. % Ge taking 6 hr., the 27 at. % Ge taking 3 hr. and the 50 at. % Ge taking 9 hr. to become ohmic. The 75 at. % Ge sample doesn’t show ohmic behavior even after 33 hr. of annealing. The metal-semiconductor interface configuration appears abrupt, showing no protrusions into the GaAs substrate.

A Materials Investigation of Nickel Based Contacts to n-SiC Subjected to Operational Thermal Stresses Characteristic of High Power Switching

1999 ◽  
Vol 572 ◽  
Author(s):  
M. W. Cole ◽  
C. W. Hubbard ◽  
C. G. Fountzoulas ◽  
D. J. Demaree ◽  
F. Ren
Keyword(s):  
Electron Microscopy ◽  
Thermal Cycling ◽  
Thermal Fatigue ◽  
Thermal Loading ◽  
Thermal Stresses ◽  
Rutherford Backscattering Spectrometry ◽  
Pulsed Power ◽  
Thermal Testing ◽  
Power Switching ◽  
Semiconductor Interface

ABSTRACTThis study developed and performed Laboratory experiments which mimic the acute cyclic thermal loading characteristic of pulsed power device switching operation. Ni contacts to n-SiC were the device components selected for cyclic thermal testing. Modifications of the contact- SIC materials properties in response to cyclic thermal fatigue were quantitatively assessed via Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM), atomic force microscopy (AFM), surface profilometry, transmission electron microscopy (TEM), nanoindentation testing and current-voltage measurements. Decreases in nanohardness and elastic modulus were observed in response to thermal fatigue. No compositional modifications were observed at the metal-semiconductor interface. Our results demonstrated that the majority of the material changes were initiated after the first thermal pulse and that the effects of subsequent thermal cycling (up to 10 pulses) were negligible. The stability of the metalsemiconductor interface after exposure to repeated pulsed thermal cycling lends support for the utilization of Ni as a contact metallization for pulsed power switching applications.

Study of SiC Device for Pulsed Power Switching Circuit

2019 ◽  
Vol 139 (8) ◽  
pp. 345-350
Author(s):  
Toru Tagawa ◽  
Tomohiko Yamashita ◽  
Takashi Sakugawa ◽  
Sunao Katsuki ◽  
Kenzi Hukuda ◽  
...  
Keyword(s):  
Pulsed Power ◽  
Switching Circuit ◽  
Power Switching

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.

Investigation of Ge, As, and Au Diffusion in Non-Alloyed Epitaxial Au-Ge Ohmic Contacts to n-GaAs Using Secondary Ion Mass Spectroscopy Backside Sputter Depth-Profiling

1991 ◽  
Vol 240 ◽  
Author(s):  
H. S. LEE ◽  
R. T. Lareau ◽  
S. N. Schauer ◽  
R. P. Moerkirk ◽  
K. A. Jones ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Ion Beam ◽  
Depth Profiling ◽  
Depth Resolution ◽  
High Concentration ◽  
Ohmic Behavior ◽  
Preferential Sputtering ◽  
Specific Contact ◽  
Secondary Ion ◽  
Diffusion Profiles

ABSTRACTA SIMS backside sputter depth-profile technique using marker layers is employed to characterize the diffusion profiles of the Ge, As, and Au in the Au-Ge contacts after annealing at 320 C for various times. This technique overcomes difficulties such as ion beam mixing and preferential sputtering and results in high depth resolution measurements since diffusion profiles are measured from low to high concentration. Localized reactions in the form of islands were observed across the surface of the contact after annealing and were composed of Au, Ge, and As, as determined by SIMS imaging and Auger depth profiling. Backside SIMS profiles indicate both Ge and Au diffusion into the GaAs substrate in the isalnd regions. Ohmic behavior was obtained after a 3 hour anneal with a the lowest average specific contact resistivity found to be ∼ 7 × 100−6 Ω- cm2.

Using reverse dynamic I–V characteristics of AlGaAs/GaAs optothyristor for pulsed power-switching applications

1992 ◽  
Vol 28 (11) ◽  
pp. 977-979 ◽  
Author(s):  
J.H. Zhao ◽  
T. Burke ◽  
D. Larson ◽  
M. Weiner ◽  
A. Chin ◽  
...  
Keyword(s):  
Pulsed Power ◽  
Power Switching

A novel high power optothyristor based on AlGaAs/GaAs for pulsed power-switching applications

1994 ◽  
Vol 41 (5) ◽  
pp. 819-825 ◽  
Author(s):  
J.H. Zhao ◽  
T. Burke ◽  
M. Weiner ◽  
A. Chin ◽  
J.M. Ballingall
Keyword(s):  
High Power ◽  
Pulsed Power ◽  
Power Switching

scholarly journals Study of SiC device for pulsed power switching circuit

2019 ◽  
Vol 209 (1-2) ◽  
pp. 3-9 ◽  
Author(s):  
Toru Tagawa ◽  
Tomohiko Yamashita ◽  
Takashi Sakugawa ◽  
Sunao Katsuki ◽  
Kenzi Hukuda ◽  
...  
Keyword(s):  
Pulsed Power ◽  
Switching Circuit ◽  
Power Switching

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.

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.

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