1. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
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Characterization of ohmic and Schottky contacts on SiC
- 1999
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 343-344, s. 637-641
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Tidskriftsartikel (refereegranskat)abstract
- The interface chemistry of nickel and tungsten based contacts on SiC has been investigated by XPS on as-deposited samples and after contact formation. After annealing at 950 °C for 10 min, Ni/SiC and Ni/Si/SiC ohmic contacts are formed due to the chemical reactions, as a result of which Ni2Si appears. However, Ni/Si (instead of pure Ni) deposition on SiC leads to modification of the diffusion processes and formation of a contact layer free of carbon. After annealing at 1200 °C for 4 min, the WN (W)/SiC systems are characterized by strong interface reactions resulting in W5Si3 and W2C formation in the contact layer. The 800 °C annealed WN/SiC contact is characterized by a chemically inert interface, and is found to be of a Schottky type.
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2. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
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Interface chemistry of a Ti/ Au/ Pt/ Ti/ SiC structure
- 1997
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 121/122, s. 208-212
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) is used to investigate the chemical reactions and diffusion processes at Ti/Au/Pt/Ti/SiC interfaces for as deposited and annealed at 575°C for 10 min structures. The distribution of the elements and the change in their chemical state has been studied. The XP spectra indicate titanium carbide and platinum silicides formation at the SiC interface, which is preceded by the dissociation of SiC due to the reactivity of Ti at 575°C. TiC represents a barrier to the further diffusion of Ti to the SiC bulk and the Ti layer makes the diffusion of Pt into SiC difficult. The element distribution of the annealed structure demonstrates that Pt has diffused through almost the whole gold layer to the surface, an alloy of the two metals being formed.
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3. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
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Interface chemistry of WN/4H-SiC structures
- 1999
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 151:3-4, s. 225-232
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Tidskriftsartikel (refereegranskat)abstract
- The interface chemistry of WN/4H–SiC structures has been studied by means of X-ray photoelectron spectroscopy (XPS). XPS investigations have been performed on as deposited, 800°C and 1200°C annealed (4 min) samples. The as deposited and 800°C annealed samples are characterized by chemically inert interfaces. Complete nitrogen out-diffusion from the WN layer, significant carbon diffusion into the contact layer, tungsten carbide and tungsten silicide formation occur during the 1200°C annealing process. The 800°C annealed WN/4H–SiC contacts are found to be of a Schottky type with a barrier height of 0.91 eV. The Schottky barrier height and the ideality factor show no significant changes during 100 h storage at 500°C under nitrogen and during operation at increasing temperature up to 350°C in air.
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4. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
-
XPS characterization of tungsten based contact layers on 4H-SiC
- 1999
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 337:1-2, s. 180-183
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Tidskriftsartikel (refereegranskat)abstract
- Annealed W (WN)/4H–SiC interfaces have been compared on the basis of X-ray photoelectron spectroscopy (XPS) studies. The 1200°C annealed W (WN)/4H–SiC structures are characterized by intense interface reactions leading to tungsten carbide and tungsten silicide formation in the contact layers. The 800°C annealed WN/4H–SiC structure exhibits a chemically inert interface, and the 800°C annealed WN/4H–SiC contact is found to be of a Schottky type with a barrier height of 0.94 eV and an ideality coefficient of 1.09.
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5. |
- Kassamakova, L., et al.
(författare)
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Thermostable Ti/Au/Pt/Ti Schottky contacts on n-type 4H-SiC
- 1998
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 13:9, s. 1025-1030
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Tidskriftsartikel (refereegranskat)abstract
- The electrical properties and interface chemistry of Ti/Au/Pt/Ti Schottky contacts to n-type 4H-SiC have been investigated with respect to their utilization for MESFETs operated at high temperatures. The electrical properties of these contacts were studied at room temperature as well as during thermal treatment. The barrier height determined from I-V characteristics was calculated to be 1.17 eV with an ideality factor of 1.09. These parameters were examined by ageing and temperature dependence tests as criteria for the thermal stability and reliability of the contacts. The barrier height and ideality factor did not change after prolonged heating at a constant temperature of and operating temperatures up to , which confirmed the contact stability. Diodes used in the measurements showed a low leakage current at 100 V reverse voltage and room temperature ( A) as well as at ( A) and breakdown voltage above 400 V. The chemical interface properties were studied by x-ray photoelectron spectroscopy for as-deposited, annealed and heated contacts. Annealing at for 10 min led to formation of TiC and in a restricted region close to the SiC interface. The data revealed a chemically stable Ti/SiC interface after annealing, which is of importance for stable rectifying characteristics during long-term operation.
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6. |
- Marinova, Ts., et al.
(författare)
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Nickel based ohmic contacts on SiC
- 1997
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Ingår i: Materials Science and Engineering B. - 0921-5107. ; 46:1-3, s. 223-226
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Tidskriftsartikel (refereegranskat)abstract
- We have compared the chemical and structural properties of Ni/SiC and Ni2Si/SiC interfaces. In the case of Ni/SiC, the contact formation is initiated by the dissociation of SiC, due to the strong reactivity of nickel at 950 °C. Ni2Si is formed and carbon accumulates, both at the interface and throughout the metal layer. At the interface, many Kirkendall voids are observed by TEM. Despite this poor interface morphology, low contact resistances have been measured. But the presence of carbon in the contact layer and at the interface is a potential source of contact degradation at high temperature. In the case of Ni/Si multilayers evaporated on SiC instead of pure Ni, the contact formation is preceded by Ni and Si mutual diffusion in the deposited layer yielding Ni2Si. Therefore, a smaller amount of carbon is released from SiC. Low carbon segregation, abrupt interface and low contact resistance characterize this contact. The thermal stability of Ni2Si contacts is illustrated with ageing experiments carried out at 500 °C.
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7. |
- Thierry-Jebali, N., et al.
(författare)
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Applications of vapor-liquid-solid selective epitaxy of highly p-type doped 4H-SiC: PiN diodes with peripheral protection and improvement of specific contact resistance of ohmic contacts
- 2014
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2. - : Trans Tech Publications. - 9783038350101 ; , s. 639-644
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Konferensbidrag (refereegranskat)abstract
- This work deals with two applications of the Selective Epitaxial Growth of highly p-type doped buried 4H-SiC in Vapor-Liquid-Solid configuration (SEG-VLS). The first application is the improvement of the Specific Contact Resistance (SCR) of contacts made on such p-type material. As a result of the extremely high doping level, SCR values as low as 1.3x10-6 Ω.cm2 have been demonstrated. Additionally, the high Al concentration of the SEG-VLS 4H-SiC material induces a lowering of the Al acceptor ionization energy down to 40 meV. The second application is the fabrication of PiN diodes with SEG-VLS emitter and guard-rings peripheral protection. Influence of some process parameters and crystal orientation on the forward and reverse characteristics of the PiN diodes is discussed. © (2014) Trans Tech Publications, Switzerland.
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