| 1. |
- Goss, J.P., et al.
(författare)
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Planar interstitial aggregates in Si
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:48, s. 12843-12853
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Tidskriftsartikel (refereegranskat)abstract
- Self-interstitials in silicon aggregate to form rod-like defects aligned along [110] directions and inhabiting either {111} or {113} crystallographic planes. These systems are known to be electrically and optically active. We present the results of first-principles calculations on the structure and energetics for candidate structures contained within the {113}, {111} and {001} planes and compare the results with experiment.
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| 2. |
- Blumenau, A.T., et al.
(författare)
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Basal plane partial dislocations in silicon carbide
- 2003
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 340, s. 160-164
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Tidskriftsartikel (refereegranskat)abstract
- Under operating conditions (forward bias) bipolar 4H- and 6H-SiC devices are known to degrade rapidly through stacking fault formation and expansion in the basal plane. It has been suggested that a recombination-enhanced dislocation glide (REDG) mechanism allows the bordering Shockley partial dislocations to overcome their barrier to glide motion and thus results in the observed stacking fault growth. In this work, we investigate the structure and properties of the participating Shockley partials by means of density functional-based atomistic calculations. Their glide motion is modelled in a process involving the formation and subsequent migration of kinks. This in combination with an analysis of the electronic structure of the partials allows an identification of those types which will be affected by the REDG mechanism.
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| 3. |
- Blumenau, A.T., et al.
(författare)
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Density functional based modelling of 30° partial dislocations in SiC
- 2004
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Ingår i: Proceedings of the 10th International Conference on Silicon Carbide and Related Materials, ICSCRM 2003. - Stafa-Zuerich : Trans Tech Publications Inc.. - 0878499431 ; , s. 453-456
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Konferensbidrag (refereegranskat)abstract
- Experiment has shown that 4H- and 6H-SiC pin diodes degrade rapidly during forward biased operation. This degradation is accompanied by the formation and expansion of stacking faults in the basal plane. It is believed that the observed rapid stacking fault growth is due to a recombination-enhanced dislocation glide (REDG) mechanism at the bordering partial dislocations. In our work we investigate the structure and properties of basal plane 30° Shockley partials in SiC by means of density functional based calculations. Barriers to their glide motion, and thus the expansion of the accompanying stacking fault is modelled in a process involving the formation and subsequent migration of kinks in the dislocation. In combination with an analysis of the electronic structure of the partials and stacking faults, this allows an identification of those types of partials which will be affected by the REDG mechanism in this model.
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| 4. |
- Blumenau, A. T., et al.
(författare)
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Dislocation related photoluminescence in silicon
- 2001
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 87:18
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Tidskriftsartikel (refereegranskat)abstract
- Dislocation related photoluminescence in Si and SiGe is attributed to stable interstitial clusters bound to 60° dislocations. Density functional based total energy calculations in Si give binding energies between 1.5 and 3.6 eV for I3 and I4 clusters with 90° and 30° partials. They possess donor levels around Ev+0.4 eV which are consistent with deep level transient spectroscopic studies on p-Si. It is further suggested that the clusters would act as the obstacles to the movement of dislocations which may have been observed in recent transmission electron microscopy studies.
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| 5. |
- Blumenau, A.T., et al.
(författare)
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Dislocations in hexagonal and cubic GaN
- 2000
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 12, s. 10223-10233
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Tidskriftsartikel (refereegranskat)abstract
- The structure and electronic activity of several types of dislocations in both hexagonal and cubic GaN are calculated using first-principles methods. Most of the stoichiometric dislocations investigated in hexagonal GaN do not induce deep acceptor states and thus cannot be responsible for the yellow luminescence. However, it is shown that electrically active point defects, in particular gallium vacancies and oxygen-related defect complexes, can be trapped at the stress field of the dislocations and may be responsible for this luminescence. For cubic GaN, we find the ideal stoichiometric 60° dislocation to be electrically active and the glide set to be more stable than the shuffle. The dissociation of the latter is considered
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| 6. |
- Blumenau, A.T., et al.
(författare)
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Optical bands related to dislocations in Si
- 2000
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 12:49, s. 10123-10129
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations are used to investigate the interaction of self-interstitial aggregates with the 90° partial dislocation in Si. We find that I4 is bound to the line with an energy of around 3 eV. The defect causes deep levels to appear in the band gap and optical transitions between these levels may account for the luminescent bands relating to plastically deformed Si.
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| 7. |
- Blumenau, A.T., et al.
(författare)
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Straight and kinked 90° partial dislocations in diamond and 3C-SiC
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:48, s. 12741-12747
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Tidskriftsartikel (refereegranskat)abstract
- Density-functional based calculations are used to investigate low energy core structures of 90° partial dislocations in diamond and 3C-SiC. In both materials dislocation glide is analysed in terms of kink formation and migration and the fundamental steps to kink migration are investigated. We find the C terminated core structure in SiC to be more mobile than the Si core. However, the Si partial is electrically active and this opens the possibility of recombination-enhanced glide under ionizing conditions or an enhanced mobility in doped material.
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| 8. |
- Blumenau, A.T., et al.
(författare)
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Structure and motion of basal dislocations in silicon carbide
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:17, s. 174108-1
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Tidskriftsartikel (refereegranskat)abstract
- 30° and 90° Shockley partial dislocations lying in {111} and basal planes of cubic and hexagonal silicon carbide, respectively, are investigated theoretically. Density-functional-based tight-binding total-energy calculations are used to determine the core structure and energetics of the dislocations. In a second step their electronic structure is investigated using a pseudopotential method with a Gaussian basis set. Finally, the thermal activation barriers to glide motion of 30° and 90° Shockley partials are calculated in terms of a process involving the formation and migration of kinks along the dislocation line. The mechanism for enhanced dislocation movement observed under current injection conditions in bipolar silicon carbide devices is discussed.
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| 9. |
- Aradi, B, et al.
(författare)
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Boron centers in 4H-SiC
- 2001
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Ingår i: Materials science Forum, Vols. 353-356. ; , s. 455-458
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Konferensbidrag (refereegranskat)abstract
- The origin of the "deep boron related acceptor level" in SIC is subject to a lot of controversy. Based on ENDOR investigations, a B-Si+V-C model was suggested, while PL studies indicated the acceptor on the carbon sublattice. Our former ab initio LDA molecular cluster calculation showed that in the B-Si+V-C complex the carbon vacancy acts as the acceptor. Now, ah initio LDA supercell calculations have been carried out for boron-related complexes to calculate the occupation levels in 4H-SiC. It has been found that the 0/- level for the B-Si+V-C complex lies in the upper half of the gap, therefore it can be disregarded as the origin of the "deep boron-related acceptor level". Investigating other feasible boron-related complexes, B-Si+Si-C appears to be the best candidate.
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| 10. |
- Blumenau, AT, et al.
(författare)
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Dislocation structures in diamond : density-functional based modelling and high-resolution electron microscopy
- 2004
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Ingår i: Defect and Diffusion Forum. - Zürich : Trans Tech Publications. - 1012-0386 .- 1662-9507. ; 226-228, s. 11-30
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Tidskriftsartikel (refereegranskat)abstract
- The core structures of perfect 60 and edge dislocations in diamond are investigated atomistically in a density-functional based tight-binding approach, and their dissociation is discussed both in terms of structure and energy. Furthermore, high resolution electron microscopy is performed on dislocation cores in high-temperature, high-pressure annealed natural brown diamond, and HRTEM image simulation allows a comparison of theoretically predicted and experimentally observed structures.
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