| 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. |
- Kortegaard Nielsen, Hanne, et al.
(författare)
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Electrically active defects in silicon produced by ion channeling
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:22, s. 3865-3867
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Tidskriftsartikel (refereegranskat)abstract
- Low-dose implantations with 65 Si and 150 keV Ge ions into the n(+) top layer of Si n(+)p diodes have been carried out. The defects produced in deeper-lying layers were studied by deep level transient spectroscopy. Results were compared to crystal-TRIM calculations and results from 2 MeV electron irradiations. Previously, ion channeling was disregarded in studies on point defect migration at room temperature using ion implantation in surface layers. In our studies, ion channeling is dominant and it overwhelms any contribution from point defect diffusion.
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| 3. |
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| 4. |
- Goubet, Olivier, et al.
(författare)
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Low-Complexity Scalable Iterative Algorithms for IEEE 802.11p Receivers
- 2015
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 64:9, s. 3944-3956
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate receivers for vehicle-to- vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. Vehicular channels are characterized by multiple paths and time variations, which introduce challenges in the design of receivers. We propose an algorithm for IEEE 802.11p-compliant receivers, based on orthogonal frequency-division multiplexing (OFDM). We employ iterative structures in the receiver as a way to estimate the channel despite variations within a frame. The channel estimator is based on factor graphs (FGs), which allow the design of soft iterative receivers while keeping acceptable computational complexity. Throughout this paper, we focus on designing a receiver that offers a good complexity-performance tradeoff. Moreover, we propose a scalable algorithm to be able to tune the tradeoff, depending on the channel conditions. Our algorithm allows reliable communications while offering a considerable decrease in computational complexity. In particular, numerical results show the tradeoff between complexity and performance measured in computational time and bit error rate (BER), as well as frame error rate (FER) achieved by various interpolation lengths used by the estimator, which both outperform by decades the standard least squares (LS) solution. Furthermore, our adaptive algorithm shows a considerable improvement in terms of computational time and complexity against state-of-the-art and classical receptors while showing acceptable BER and FER performance.
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