| 1. |
- Aradi, B., et al.
(författare)
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Impurity-controlled dopant activation : Hydrogen-determined site selection of boron in silicon carbide
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 79:17, s. 2746-2748
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Tidskriftsartikel (refereegranskat)abstract
- The geometry and formation energy of substitutional B and Al dopants as well as their complexes with hydrogen have been calculated in 4H-SiC using first-principles methods. Our results show that boron selecting the silicon site and, therefore, getting activated as a shallow acceptor depends on the presence of hydrogen which is promoted into the crystal by boron itself. Without hydrogen, boron would mostly be incorporated at the carbon site. Aluminum does not show this behavior: it always selects the silicon site and is incorporated independently of hydrogen. © 2001 American Institute of Physics.
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| 2. |
- Deak, P, et al.
(författare)
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A cause for SiC/SiO2 interface states : The site selection of oxygen in SiC
- 2003
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Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 535-538
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Konferensbidrag (refereegranskat)abstract
- We show that in the SiC/SiO2 system the interface states in the lower half of the gap are the consequence of the behavior of oxygen in SiC. Investigating the elemental steps of oxidation on a simple model by means of ab initio density functional calculations we find that, in course of the oxidation, carbon-vacancy (V-C) - oxygen complexes constantly arise. The V-C+O complexes have donor states around E-V+0.8 eV. Their presence gives rise to a thin transition layer which is not SiO2 but an oxygen contaminated Si-rich interface layer producing the aforementioned gap states.
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| 3. |
- Gali, Adam, et al.
(författare)
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Aggregation of carbon interstitials in silicon carbide : A theoretical study
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:12
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio supercell calculations have been carried out to investigate clusters of carbon interstitials in 3C- and 4H-SiC. Based on the calculated formation energies, the complex formation of carbon interstitials or their aggregation to carbon antisites is energetically favored in SiC. The electronic and vibronic properties of the carbon interstitials and their aggregates depends strongly on the polytype. Using the calculated hyperfine constants and local vibrational modes of carbon clusters the possible relation to known carbon-related centers will be discussed.
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| 4. |
- Deak, P, et al.
(författare)
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Vacancies and their complexes with H in SiC
- 2000
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Ingår i: Materials Science Forum, Vols. 338-343. - Stafa-Zurich, Switzerland : Trans Tech Publications Inc.. ; , s. 817-820
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Konferensbidrag (refereegranskat)abstract
- Ab initio calculations (LDA and MCSF) have been carried out for vacancies (V-Si and V-C) and interstitial H, as well as for V+H complexes in 3C SiC. Relative stability of different charge-states/configurations and occupation levels were determined in supercells with plane wave basis sets while vibration frequencies and spin distributions were calculated in clusters with localized basis functions. Both types of vacancies show amphoteric electrical activity. In equilibrium, atomic He is at the AB(C), and H is at the T-Si site, while H-0 does not appear to be stable with respect to them, so H can also act both as a deep donor and an electron trap. Hydrogen can passivate the V-Si acceptor but not the V-C donor. Conditions for the formation of the possible V+H centers and their properties are given and used to discuss experimental information (or the lack of them) about H in SiC.
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| 5. |
- Gali, A, et al.
(författare)
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Activation of shallow boron acceptor in CB coimplanted silicon carbide : A theoretical study
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:10, s. 102108-
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio supercell calculations have been carried out to investigate the complexes of boron acceptors with carbon self-interstitials in cubic silicon carbide. Based on the calculated binding energies, the complex formation of carbon interstitials with shallow boron acceptor and boron interstitial is energetically favored in silicon carbide. These bistable boron defects possess deep, negative- U occupation levels in the band gap. The theoretical results can explain the observed activation rates in carbon-boron coimplantation experiments. © 2005 American Institute of Physics.
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| 6. |
- Gali, Adam, et al.
(författare)
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Anti-site pair in SiC : A model of the DI center
- 2003
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Ingår i: Physica B. - : Elsevier BV. ; , s. 175-179
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Konferensbidrag (refereegranskat)abstract
- The DI low-temperature photoluminescence center is a well-known defect stable up to 1700°C annealing in SiC, still its structure is not known after decades of study. Combining experimental and theoretical studies in this paper we will show that the properties of an anti-site pair can reproduce the measured one-electron level position and local vibration modes of the D I center and the model is consistent with other experimental findings as well. We give theoretical values of the hyperfine constants of the anti-site pair in its paramagnetic state as a means to confirm our model. © 2003 Elsevier B.V. All rights reserved.
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| 7. |
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| 8. |
- Gali, Adam, et al.
(författare)
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Correlation between the antisite pair and the D-I center in SiC
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:15
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Tidskriftsartikel (refereegranskat)abstract
- The D-I low temperature photoluminescence center is a well-known defect stable up to 1700 degreesC annealing in SiC, still its structure is not yet known. Combining experimental and theoretical studies, in this paper we will show that the properties of an antisite pair can reproduce the measured one-electron level position and local vibration modes of the D-I center, and are consistent with other experimental findings as well. We give theoretical values of the hyperfine constants of the antisite pair in its paramagnetic state as a means to confirm a model.
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| 9. |
- Gali, Adam, et al.
(författare)
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Overcoordinated hydrogens in the carbon vacancy : Donor centers of SiC
- 2000
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 84:21, s. 4926-4929
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial silicon carbide is likely to contain hydrogen and vacancies (V), therefore, V + nH complexes are likely to influence its electronic properties. Using ob initio calculations we show that neutral and positive H atoms are trapped by carbon vacancies (V-C) in three-center bonds with two Si neighbors. The double positive charge state of V-C + H is not stable in equilibrium and in the triply positive state H binds only to one of the Si neighbors. At most two H atoms can be accommodated by a single V-C. The V-C + nH complexes have donor character and exhibit rather atypical vibration modes for Si-H bonds. Occupation levels and spin distributions were calculated and compared fur V-C + H and V-C.
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| 10. |
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