Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC

Tsukimoto, Susumu; Nitta, Koji; Sakai, T.; Moriyama, Miki; Murakami, Masanori

doi:10.1007/s11664-004-0203-x

Cited by 68 publications

(62 citation statements)

References 31 publications

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“…For MAX phases, the most well-known example of the first category of reactions is Ti 3 SiC 2 which is often found at the interface when Ti and SiC are in contact at higher temperatures, e.g., when Ti is used as braze material to bond SiC to SiC or in Ti-reinforced SiC metal matrix composites [3]. The most relevant example as a thin-film synthesis method is Ti 3 SiC 2 synthesized by annealing of Ti-based contacts used as electrodes in SiC-based semiconductor devices [191,192,193,194]. Another example relevant to the semiconductor industry is Ti 2 GaN which can form at the interface between Ti-based films on GaN substrates [195].…”

Section: Solid-state Reactionsmentioning

confidence: 99%

“…MAX phases synthesized by solid state reactions or sputter deposition can potentially be used as electrodes in SiC-, AlN-, or GaN-based semiconductor devices or sensor applications [195,198,326]. "Ti-based" contacts to SiC are in use and typically contain Ti 3 SiC 2 formed by solid state reactions [191,192,326]. A more exotic suggestion is the claim (based on theoretical calculations of the dielectric function and infrared emittance [327,328]) that Ti 4 AlN 3 and V 4 AlC 3 have the potential to be used as a coating on spacecrafts to avoid solar heating and also increase the radiative cooling in future space missions to Mercury.…”

Section: Applicationsmentioning

confidence: 99%

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The M+1AX phases: Materials science and thin-film processing

et al. 2010

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This article is a critical review of the M n+1 AX n phases ("MAX phases", where n =1, 2, or 3) from a materials science perspective. MAX phases are a class of hexagonal-structure ternary carbides and nitrides ("X") of a transition metal ("M") and an A-group element. The most well known are Ti 2 AlC, Ti 3 SiC 2 , and Ti 4 AlN 3 . There are ~60 MAX phases with at least 9 discovered in the last five years alone. What makes the MAX phases fascinating and potentially useful is their remarkable combination of chemical, physical, electrical, and mechanical properties, which in many ways combine the characteristics of metals and ceramics. For example, MAX phases are typically resistant to oxidation and corrosion, elastically stiff, but at the same time they exhibit high thermal and electrical conductivities and are machinable. These properties stem from an inherently nanolaminated crystal structure, with M n+1 X n slabs intercalated with pure A-element layers. The research on MAX phases has been accelerated by the introduction of thin-film processing methods.Magnetron sputtering and arc deposition have been employed to synthesize single-crystal material by epitaxial growth, which enables studies of fundamental materials properties. However, the surface-initiated decomposition of M n+1 AX n thin films into MX compounds at temperatures of 1000-1100 °C is much lower than the decomposition temperatures typically reported for the corresponding bulk material. We also review the prospects for low-temperature synthesis, which is essential for deposition of MAX phases onto technologically important substrates. While deposition of MAX phases from the archetypical Ti-Si-C and Ti-Al-N systems typically require synthesis temperatures of ~800 °C, recent results have demonstrated that V 2 GeC and Cr 2 AlC can be deposited at ~450 °C. Also, thermal spray of Ti 2 AlC powder has been used to produce thick coatings. We further treat progress in the use of first-principles calculations for predicting hypothetical MAX phases and their properties. Together with advances in processing and materials 3 analysis, this progress has led to recent discoveries of numerous new MAX phases such as Ti 4 SiC 3 , Ta 4 AlC 3 , and Ti 3 SnC 2 . Finally, important future research directions are discussed. These include charting the unknown regions in phase diagrams to discover new equilibrium and metastable phases, as well as research challenges in understanding their physical properties, such as the effects of anisotropy, impurities, and vacancies on the electrical properties, and unexplored properties such as superconductivity, magnetism, and optics. 4

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Section: Solid-state Reactionsmentioning

confidence: 99%

Section: Applicationsmentioning

confidence: 99%

The M+1AX phases: Materials science and thin-film processing

et al. 2010

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“…Thus, a current transport mechanism between metal/implanted SiC interface is not clearly understood. In our previous paper [8], we reported that the lower r c values of the p-type 4H-SiC layers using Ti/Al and Ni/Ti/Al contacts were due to the formation of Ti 3 SiC 2 layers at the interfaces between the as-deposited Ti/Al or Ni/Ti/Al metals and p-type 4H-SiC layers.…”

Section: Introductionmentioning

confidence: 89%

Effects of Al ion implantation to 4H-SiC on the specific contact resistance of TiAl-based contact materials

Ito

Tsukimoto

Murakami

2006

Science and Technology of Advanced Materials

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To realize high-performance silicon carbide (SiC) power devices, low-resistance ohmic contacts to p-type SiC must be developed. To reduce the ohmic contact resistance, reduction of the barrier height at metal/SiC interfaces or increase in the doping concentration in the SiC substrates is needed. Since the reduction of barrier height is extremely difficult, the increase in the Al doping concentration in 4H-SiC by an ion-implantation technique was challenged. The Ti/Al and Ni/Ti/Al metals (where a slash ''/'' sign indicates the deposition sequence) were deposited on the Al ion-implanted SiC substrates. By comparing the experimental and theoretical contact resistances, the current transport mechanism through the metal/SiC interfaces was concluded to be thermionic field emission and the barrier height was determined to be $0.4 eV. Although the hole concentration increased with increasing the Al doping concentration in 4H-SiC, the barrier height at metal/SiC interfaces increased due to high density of dislocation loops observed in the implanted SiC layers by transmission electron microscopy. The present experiments suggested that the low-resistance ohmic contacts would be formed when a technique to eliminate the crystal defects formed in the 4H-SiC substrates after ion implantation was developed. r

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“…Tanimoto et al examined the microstructure at the interface between TiAl contacts and the SiC using Auger electron spectroscopy and found that carbides containing Ti and Si were formed at interface (Tanimoto et al, 2002). Recently, transmission electron microscopy (TEM) studies by Tsukimoto et al have provided useful information in this aspect due to possible high-resolution imaging (Tsukimoto et al, 2004). They have found that the majority of compounds generated on the surface of 4H-SiC substrate after annealing consist of a newly formed compound and hence proposed that the new interface is responsible for the lowering of Schottky barrier in the TiAl-based contact system.…”

Section: Introductionmentioning

confidence: 99%