| 1. |
- Hallin, Christer, et al.
(författare)
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Improved Ni ohmic contact on n-type 4H-SiC
- 1997
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 26:3, s. 119-122
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the structural, chemical and electronic properties of Al/Ni/ Al-layers evaporated on 4H silicon carbide and then annealed at 1000°C for 5 min. The structure was investigated before and after annealing by transmission electron spectroscopy from cross-sectional specimens. With x-ray photoelectron spectroscopy, both element distribution and bonding energies were followed during sputtering through the alloyed metal-semiconductor contact. Voids are found in both annealed Ni/4H-SiC and Al/Ni/Al/4H-SiC contact layers, though closer to the metal-semiconductor interface in the former case. The first aluminum-layer is believed to prevent voids to be formed at the interface and also to reduce the oxide on the semiconductor surface. The contact was found to be ohmic with a specific contact resistance ρc - 1.8 × 10−5 Ωcm2 which is more than three times lower ρc than for the ordinary Ni/4H-SiC contact prepared in the same way.
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| 2. |
- 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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| 3. |
- Kasamakova-Kolaklieva, L, et al.
(författare)
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Characteristics of Ni Schottky contacts on compensated 4H-SiC layers
- 2003
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Ingår i: Materials Science Forum, Vols. 433-436. - : Trans Tech Publications. ; , s. 709-712
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Konferensbidrag (refereegranskat)abstract
- The electrical properties of Ni Schottky contacts to compensated 4H-SiC layers have been characterized by means of IN and C-V measurements and the key parameters have been determined. The measured barrier heights were between 0.90 eV and 2.90 eV depending on the conductivity type and the donor/acceptor concentration as well as the measurement techniques used. Inhomogeneties in IN characteristics of some rectifiers at lower forward-bias voltages have been observed. This may suggest enhanced trapping mechanism due to the nonuniform boron compensation of the epilayers.
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| 4. |
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| 5. |
- Kassamakova, L, et al.
(författare)
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Al/Si ohmic contacts to p-type 4H-SiC for power devices
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 338-3, s. 1009-1012
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Tidskriftsartikel (refereegranskat)abstract
- The formation of Al/Si/p-4H SiC ohmic contacts at temperatures as low as 750 degreesC is reported in this paper. The dependence of electrical properties and contact morphology have been investigated as a function of the annealing regime in the interval 600-700 degreesC. The lowest contact resistivity of 3.8x10(-5) Omega .cm(2) was obtained at 700 degreesC annealing, however the most reproducible results were in the low 10(-4) Omega .cm(2) range. It has been established that the predominate current transport mechanism in the Al/Si/SiC contacts is thermionic-field emission. Atomic force microscopy showed that the addition of Si to the contact layer improves its morphology, and the pitting of annealed Al is not observed. The contacts developed are stable during ageing at 500 degreesC and at operating temperatures up to 450 degreesC. After the contacts testing with current density of 10(3) A/cm(2) at temperatures up to 450 degreesC, their contact resistivity decreases slightly.
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| 6. |
- Kassamakova, L, et al.
(författare)
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Effect of temperature treatment on Au/Pd Schottky contacts to 4H-SiC
- 2002
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Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 929-932
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Konferensbidrag (refereegranskat)abstract
- Au/Pd/SiC Schottky baffler contacts have been formed on n-type 4H-SiC grown by sublimation epitaxy. The effect of annealing temperature on the electrical properties of these contacts was studied using IN and C-V measurements. The barrier height was found to increase slightly from 1.14 eV for as-deposited contacts to 1.2 eV after annealing at 500 degreesC, while the more pronounced effect was observed with decrease of the ideality factor, Auger analysis was used to study the metallurgy of the annealed contacts. Strong diffusion between Au and Pd was established after 500 degreesC anneal, while the Pd/SiC interface remained almost steep, The electrical properties of annealed contacts have been study during the thermal treatment at temperatures up to 350 degreesC and prolonged ageing at 300 degreesC and 400 degreesC in nitrogen.
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| 7. |
- Kassamakova, L, et al.
(författare)
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Study of the electrical, thermal and chemical properties of Pd ohmic contacts to p-type 4H-SiC : dependence on annealing conditions
- 1999
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Ingår i: Materials Science and Engineering: B. - 0921-5107 .- 1873-4944. ; 61-62, s. 291-295
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Tidskriftsartikel (refereegranskat)abstract
- The electrical and chemical properties of Pd ohmic contacts to p-type 4H-SiC, together with their thermal stability, have been studied in the annealing temperature range 600–700°C. The ohmic behaviour of as-deposited and annealed contacts has been checked from I–V characteristics and the contact resistivity has been determined by the linear TLM method in order to determine the electrical properties and the thermal stability. An ohmic behaviour was established after annealing at 600°C, while the lowest contact resistivity 5.5×10−5 Ω.cm2 was obtained at 700°C. The contact structure, before and after annealing, was investigated using X-ray photoelectron spectroscopy depth analysis. As-deposited Pd films form an abrupt and chemically inert Pd/SiC interface. Annealing causes the formation of palladium silicide. After formation at 600°C the contact structure consists of unreacted Pd and Pd3Si. During annealing at 700°C, Pd and SiC react completely and a mixture of Pd3Si, Pd2Si and C in a graphite state is found in the contact layer. The examination of the thermal stability shows that after a 100 h heating at 500°C, only the contacts annealed at 700°C did not suffer from a change in resistivity. This can be explained by a more complete reaction between the Pd contact layer and the SiC substrate at this higher annealing temperature.
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| 8. |
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| 9. |
- Kassamakova, L, et al.
(författare)
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Thermostable ohmic contacts on p-type SiC
- 1998
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Ingår i: SILICON CARBIDE, III-NITRIDES AND RELATED MATERIALS, PTS 1 AND 2. - 0878497900 ; , s. 787-790
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Konferensbidrag (refereegranskat)
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| 10. |
- 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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