| 1. |
- 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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| 2. |
- Thierry-Jebali, N., et al.
(författare)
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Very low specific contact resistance measurements made on a highly p-type doped 4H-SiC layer selectively grown by vapor-liquid-solid transport
- 2013
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 102:21, s. 212108-
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Tidskriftsartikel (refereegranskat)abstract
- This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper.
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| 3. |
- Elgán, Tobias H., et al.
(författare)
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Determinants of activity in glutaredoxins : An in vitro evolved Grx1-like variant of Escherichia coli Grx3
- 2010
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 430:3, s. 487-495
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Tidskriftsartikel (refereegranskat)abstract
- The Escherichia coli glutaredoxins 1 and 3 (Grx1 and Grx3) are structurally similar (37% sequence identity), yet have different activities in vivo. Unlike Grx3, Grx1 efficiently reduces protein disulfides in proteins such as RR (ribonucleotide reductase), whereas it is poor at reducing S-glutathionylated proteins. An E. coli strain lacking genes encoding thioredoxins 1 and 2 and Grx1 is not viable on either rich or minimal medium; however, a M43V mutation in Grx3 restores growth under these conditions and results in a Grx1-like protein [Ortenberg, Gon, Porat and Beckwith (2004) Proc. Natl. Acad. Sci. U.S.A. 101, 7439-7944]. To uncover the structural basis of this change in activity, we have compared wild-type and mutant Grx3 using CD and NMR spectroscopy. Ligand-induced stability measurements demonstrate that the Grx3(M43V/C65Y) mutant has acquired affinity for RR. Far-UV CD spectra reveal no significant differences, but differences are observed in the near-UV region indicative of tertiary structural changes. NMR 1H- 15N HSQC (heteronuclear single quantum coherence) spectra show that approximately half of the 82 residues experience significant (Δδ > 0.03 p.p.m.) chemical shift deviations in the mutant, including nine residues experiencing extensive (Δδ ≥ 0.15 p.p.m.) deviations. To test whether the M43V mutation alters dynamic properties of Grx3, H/D (hydrogen/deuterium) exchange experiments were performed demonstrating that the rate at which backbone amides exchange protons with the solvent is dramatically enhanced in the mutant, particularly in the core of the protein. These data suggest that the Grx1-like activity of the Grx3(M43V/C65Y) mutant may be explained by enhanced intrinsic motion allowing for increased specificity towards larger substrates such as RR.
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| 4. |
- Thierry-Jebali, N, et al.
(författare)
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Observation of the generation of stacking faults and active degradation measurements on off-axis and on-axis 4H-SiC PiN diodes
- 2012
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 101:22, s. 222111-
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Tidskriftsartikel (refereegranskat)abstract
- PiN diodes have been fabricated on nominally on-axis Si-face 4H-SiC material and their electrical characteristics are compared to PiN diodes processed with exactly the same device process recipe on 8 degrees-off 4H-SiC material. Some diodes had an optical window on the top metal contact to observe the possible stacking faults generation and motion with photo emission microscopy. The diodes were electrically characterized in forward voltage to test their stability. Electrical characterizations demonstrate that there is no noticeable degradation for the diodes processed on on-axis 4H-SiC substrate and with optical characterization the formation of stacking faults was not observed.
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