| 1. |
- Syväjärvi, Mikael, et al.
(author)
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Fluorescent SiC as a new material for white LEDs
- 2012
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In: Physica scripta. T. - 0281-1847 .- 0031-8949 .- 1402-4896. ; T148, s. 014002-
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Journal article (peer-reviewed)abstract
- Current III–V-based white light-emitting diodes (LEDs) are available. However, their yellow phosphor converter is not efficient at high currents and includes rare-earth metals, which are becoming scarce. In this paper, we present the growth of a fluorescent silicon carbide material that is obtained by nitrogen and boron doping and that acts as a converter using a semiconductor. The luminescence is obtained at room temperature, and shows a broad luminescence band characteristic of donor-to-acceptor pair recombination. Photoluminescence intensities and carrier lifetimes reflect a sensitivity to nitrogen and boron concentrations. For an LED device, the growth needs to apply low-off-axis substrates. We show by ultra-high-resolution analytical transmission electron microscopy using aberration-corrected electrons that the growth mechanism can be stable and that there is a perfect epitaxial relation from the low-off-axis substrate and the doped layer even when there is step-bunching.
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| 2. |
- Aberg, D, et al.
(author)
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Ultra-shallow thermal donor formation in oxygen-containing ambient
- 1998
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In: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 210, s. 527-532
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Journal article (peer-reviewed)abstract
- Czochralski-grown phosphorus-doped (approximate to 2 x 10(14) cm(-3)) silicon wafers have been annealed in nitrogen, wet nitrogen, argon, oxygen, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made with capacitance-voltage, four-point probe, DLTS, thermally stimulated capacitance, admittance spectroscopy, secondary ion-mass spectrometry, and Fourier transform infrared spectroscopy. This study finds a strong relation between the previously reported ultra-shallow thermal donors (USTDs) and shallow thermal donors (STDs), and it is shown that the net concentration of thermally formed donors is independent on annealing ambient within the experimental accuracy. It was found that the majority of formed donors for long anneals consisted of either STDs or USTDs, however, it was found that oxygen-containing ambient is indispensable for forming USTDs.
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| 3. |
- Aberg, D, et al.
(author)
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Ultrashallow thermal donor formation in silicon by annealing in ambient oxygen
- 1999
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In: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 85, s. 8054-8059
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Journal article (peer-reviewed)abstract
- Czochralski-grown silicon wafers doped with phosphorus (similar to 10(14) cm(-3)) have been annealed in nitrogen, wet nitrogen, oxygen, argon, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made using predominantly electrical techniques such as admittance spectroscopy and thermally stimulated capacitance measurements but also secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy were employed. In all samples, an increasing concentration of free carrier electrons is observed with increasing annealing time, reaching a maximum of similar to 10(16) cm(-3) at 100 h. For durations in excess of 100 h gradual decrease of the free electron concentration takes place except for the samples treated in wet nitrogen and oxygen atmospheres, which display donors stable even after 200 h. These stable centers are found to have shallower donor level positions in the energy band gap (similar to 25 meV below the conduction band edge E-c) than those of the centers formed in vacuum, argon, and nitrogen atmospheres (similar to 35 meV below E-c). The latter centers are associated with the well-established shallow thermal donors (STDs) while the origin of the former ones, which are labeled ultrashallow thermal donors (USTDs) is less known. However, on the basis of a wealth of experimental results we show that the USTDs are most likely perturbated STDs modified through interaction with fast-in diffusing oxygen species, possibly oxygen dimers. Further, comparison between the electrical data and the SIMS measurements reveals unambiguously that neither the STD nor the USTD centers involve nitrogen, in contrast to recent suggestions in the literature. (C) 1999 American Institute of Physics. [S0021-8979(99)06512-3].
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| 4. |
- Achtziger, N, et al.
(author)
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Formation of passivated layers in p-type SiC by low energy ion implantation of hydrogen
- 2000
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In: SILICON CARBIDE AND RELATED MATERIALS - 1999 PTS, 1 & 2. ; , s. 933-936
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Conference paper (peer-reviewed)abstract
- The mobility of hydrogen and its passivating effect on accepters in p-type SiC is investigated. Hydrogen (isotope H-1 or H-2 alternatively) is implanted at temperatures between 300 K and 680 K with low energy (300 eV per atom) in order to minimize implantation damage. The depth profiles of 2H and of passivated accepters correspond closely. Up to 500 K, a fully passivated layer with a well defined thickness is formed. Its depth ton the order of 1 micrometer) is investigated as a function of doping level and hydrogen fluence. At higher temperatures, the incorporation drastically increases, but the electrical passivation is partial only. Qualitative explanations are given.
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| 5. |
- Achtziger, N, et al.
(author)
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Hydrogen passivation of silicon carbide by low-energy ion implantation
- 1998
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 73, s. 945-947
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Journal article (peer-reviewed)abstract
- implantation of deuterium is performed to investigate the mobility and passivating effect of hydrogen in epitaxial alpha-SiC (polytypes 4H and 6H). To avoid excessive damage and the resulting trapping of hydrogen, the implantation is performed with low energy (600 eV H-2(2)+). The H-2 depth profile is analyzed by secondary ion mass spectrometry. Electrical properties are measured by capacitance-voltage profiling and admittance spectroscopy. In p-type SIG, hydrogen diffuses on a mu m scale even at room temperature and effectively passivates accepters. In n-type SiC, the incorporation of H is suppressed and no passivation is detected. (C) 1998 American Institute of Physics.
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| 6. |
- Achtziger, N, et al.
(author)
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Mobility passivating effect and thermal stability of hydrogen in silicon carbide
- 1998
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In: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 210, s. 395-399
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Journal article (peer-reviewed)abstract
- The diffusion and passivating effect of hydrogen (isotope H-2) in epitaxial p-type SiC is studied by secondary ion mass spectrometry and capacitance-voltage profiling on Schottky diodes. The incorporation of hydrogen is achieved by low-energy ion implantation. The influence of implantation energy, temperature and subsequent annealing is presented. Annealing experiments with an electric field applied reveal a reactivation of passivated accepters and a H+ ion drift at a surprisingly low temperature of 530 K.
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| 7. |
- Doyle, J P, et al.
(author)
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Observation of near-surface electrically active defects in n-type 6H-SiC
- 1998
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 83, s. 3649-3651
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Journal article (peer-reviewed)abstract
- In n-type 6H-SiC epitaxial layers grown by vapor phase epitaxy, we find that in contrast to the majority of the epitaxial layer, where electrically active defects are observed with a concentration less than 1 X 10(-13) cm(-3), a region near the front surface contains defects with concentrations approaching 10(14) cm(-3). A relationship between the near-surface defects and metallic impurities is suggested by a Ti concentration of 1 X 10(16) cm(-3) in this region. The high concentration of near surface defects is found to significantly reduce the carrier lifetime. (C) 1998 American Institute of Physics. [S0021-8979(98)03007-2].
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| 8. |
- Forsberg, Urban, 1971-, et al.
(author)
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Aluminum doping of epitaxial Silicon Carbide
- 2003
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In: Journal of Crystal Growth. - : ScienceDirect. - 0022-0248 .- 1873-5002. ; 253:1-4, s. 340-350
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Journal article (peer-reviewed)abstract
- Intentional doping of aluminum in 4H and 6H SiC has been performed using a hot-wall CVD reactor. The dependence of aluminum incorporation on temperature, pressure, C/Si ratio, growth rate, and TMA flow has been investigated. The aluminum incorporation showed to be polarity dependent. The high aluminum incorporation on the Si-face is closely related to the carbon coverage on the SiC surface. Changes in process parameters changes the effective C/Si ratio close to the SiC surface. Increased growth rate and C/Si ratio increases the aluminum incorporation on the Si-face. Diffusion limited incorporation occurs at high growth rate. Reduced pressure increases the effective C/Si ratio, and at low growth rate, the aluminum incorporation increases initially, levels off at a critical pressure, and continues to decrease below the critical pressure. The aluminum incorporation showed to be constant in a temperature range of 50°C. The highest atomic concentration of aluminum observed in this study was 3×1017 and 8×1018 cm−3 in Si and C-face, respectively.
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| 9. |
- Forsberg, U, et al.
(author)
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Aluminum doping of epitaxial silicon carbide grown by hot-wall CVD; Effect of process parameters
- 2002
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In: SILICON CARBIDE AND RELATED MATERIALS 2001, PTS 1 AND 2, PROCEEDINGS. ; , s. 203-206
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Conference paper (peer-reviewed)abstract
- Intentional p-type doping of SiC has been performed by using trimethylaluminum as dopant source. A comprehensive investigation of the aluminum incorporation dependency on temperature, pressure, C/Si ratio and growth rate in a horizontal hot-wall CVD reactor has been made. The incorporation mechanism for 4H and 6H-SiC both for Si- and C-face material is presented.
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| 10. |
- Forsberg, Urban, 1971-, et al.
(author)
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Growth and characterisation 4H-SiC MESFET structures grown by Hot-Wall CVD
- 2001
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In: Proc. of the MRS 2000 Fall Meeting. ; , s. H2.3.2-
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Conference paper (peer-reviewed)abstract
- Metal semiconductor field effect transistor structures have been grown in a hot-wall CVD reactor. Using trimethylaluminium and nitrogen, p- and n-type epitaxial layers were grown on semi insulating substrates. A comprehensive characterization study of thickness and doping of these multi structures has been performed by using scanning electron microscopy , secondary ion mass spectrometry, capacitance-voltage and low temperature photoluminescence. Optimisation of growth parameters has resulted in very abrupt doping profiles. The grown metal semiconductor field effect transistor structures have been processed and parts of the transistor properties are presented.
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