| 1. |
- Bruzzi, M, et al.
(författare)
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Radiation-hard semiconductor detectors for SuperLHC
- 2005
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 541:1-2, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.
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| 2. |
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| 3. |
- Neimontas, K, et al.
(författare)
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Optical studies of nonequilibrium carrier dynamics in highly excited 4H-SiC epitaxial layers
- 2005
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Ingår i: Materials Science Forum, Vols. 483-485. ; , s. 413-416
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Konferensbidrag (refereegranskat)abstract
- We applied picosecond four-wave mixing technique to investigate carrier diffusion and recombination in n-type 4H-SiC epilayers. The dependence of bipolar diffusion coefficient D on photocarrier density was measured in range from &SIM, 10(17) to 10(20) Cm-3. We determined a decrease of D value from 3.4 to 2.2 cm(2)/S with increase of the photoexcitation level in range from &SIM, 10(17) to &SIM, 10(19) cm(-3), and found its increase up to 3.8 cm(2)/s at carrier density above 1020 cm(-3). Auger recombination governed decrease of carrier lifetime from 11 ns at &SIM, 10(17) cm(-3) to 1.8 ns at &SIM, 10(20) cm(3) has also been observed.
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| 4. |
- Neimontas, K., et al.
(författare)
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The determination of high-density carrier plasma parameters in epitaxial layers, semi-insulating and heavily doped crystals of 4H-SiC by a picosecond four-wave mixing technique
- 2006
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 21:7, s. 952-958
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Tidskriftsartikel (refereegranskat)abstract
- We applied a picosecond four-wave mixing technique for measurements of carrier lifetimes and diffusion coefficients in highly excited epitaxial layers, semi-insulating and heavily doped 4H-SiC substrates. Optical carrier injection at two different wavelengths (266 and 355 nm) allowed us to vary the depth of the excited region from 1-2 νm to 50 νm, and thus determine photoelectric parameters of carrier plasma in the density range from 2 × 1016 to 1019 cm-3. Strong dependence of carrier lifetime and mobility on carrier density was found in the epitaxial layers. The origin of fast decay components, not resolved previously by photoluminescence and free-carrier absorption techniques in SiC, was attributed to nonlinear carrier recombination. Numerical modelling provided a value of bimolecular recombination coefficient equal to B ≤ (2-4) × 10-11 cm3 s-1 and verified a surface recombination velocity S ≤ 4 × 104 cm s-1. In heavily doped crystals, nonlinear carrier recombination reduced the carrier lifetime down to 1.1 ns, while in semi-insulating ones a lifetime of 1.5-2.5 ns was measured. Temperature dependences of four-wave mixing provided monopolar carrier mobility in heavily doped and bipolar one in semi-insulating crystals, and revealed the contribution of ionized impurity and phonon scattering mechanisms. © 2006 IOP Publishing Ltd.
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| 5. |
- Storasta, Liutauras, et al.
(författare)
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Nonequilibrium carrier diffusion and recombination in heavily-doped and semi-insulating bulk HTCVD grown 4H-SiC crystals
- 2005
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Ingår i: Materials Science Forum, Vols. 483-485. ; , s. 409-412
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Konferensbidrag (refereegranskat)abstract
- We applied four-wave mixing (FWM) technique for investigation of high temperature chemical vapour deposition (HTCVD) grown 4H-SiC samples with different doping levels. The determined minority electron and hole mobilities in heavily doped crystals at doping densities of 1019 cm(-3) were found to be equal to 116 and 52 cm(2)/Vs. In semi-insulating (SI) crystals, the ambipolar diffusion coefficient Da = 2.6 - 3.3 cm(2) A and carrier lifetimes of 1.5 - 2.5 ns have been measured. Irradiation of SI crystals by 6 MeV electrons resulted in essential decrease of carrier lifetime down to &SIM, 100 ps and clearly revealed the defect-assisted carrier generation with respect to two-photon interband transitions before irradiation.
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