| 1. |
- Nylandsted Larsen, A., et al.
(författare)
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Tin-vacancy acceptor levels in electron-irradiated n-type silicon
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:7, s. 4535-4544
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Tidskriftsartikel (refereegranskat)abstract
- Si crystals (n-type, fz) with doping levels between 1.5×1014 and 2×1016 cm-3 containing in addition ∼1018 Sn/cm3 were irradiated with 2-MeV electrons to different doses and subsequently studied by deep level transient spectroscopy, Mössbauer spectroscopy, and positron annihilation. Two tin-vacancy (Sn-V) levels at Ec-0.214 eV and Ec-0.501 eV have been identified (Ec denotes the conduction band edge). Based on investigations of the temperature dependence of the electron-capture cross sections, the electric-field dependence of the electron emissivity, the anneal temperature, and the defect-introduction rate, it is concluded that these levels are the double and single acceptor levels, respectively, of the Sn-V pair. These conclusions are in agreement with electronic structure calculations carried out using a local spin-density functional theory, incorporating pseudopotentials to eliminate the core electrons, and applied to large H-terminated clusters. Thus, the Sn-V pair in Si has five different charge states corresponding to four levels in the band gap.
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| 2. |
- Janson, M S, et al.
(författare)
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Diffusion of dopants and impurities in device structures of SiC, SiGe and Si
- 2001
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Ingår i: DIFFUSIONS IN MATERIALS. ; , s. 597-609
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Konferensbidrag (refereegranskat)abstract
- Silicon Carbide (SiC) has a high thermal stability and for most elements temperatures in excess of 2000 degreesC are anticipated to reach reasonable diffusivities (greater than or equal to 10(-13) cm(2)/s). We demonstrate, however, that light elements, like hydrogen and lithium, exhibit a considerable mobility already at less than or equal to 400 degreesC, Technologically, the principal interest in these light elements arises because of their ability to electrically passivate shallow acceptors and donors as well as deep level defects in common semiconductors (SiC, Si, GaAs). Indeed, for both hydrogen and lithium the diffusion kinetics is shown to be strongly affected by trapping and de-trapping at boron impurities in the SiC layers. Evidence is also provided that hydrogen migrates as a positively charged ion in p-type SiC. Furthermore, similar to that in crystalline silicon, transient enhanced diffusion of ion-implanted boron is observed in SiC. The initial boron diffusivity during postimplant annealing at 1600 degreesC is enhanced by more than two orders of magnitude compared to equilibrium conditions. For Silicon Germanium (SiGe) diffusion of the n-type dopants Sb and P is studied. Comparing results from strained and relaxed SiGe layers annealed under inert and oxidizing conditions it is unambiguously shown that the diffusion of Sb is almost exclusively mediated by vacancies. On the other hand, P diffusion is predominantly assisted by Si self-interstitials and in this case compositional and strain effects in the SiGe layers are competing.
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