| 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. |
- Davies, G, et al.
(författare)
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Optical properties of a silver-related defect in silicon
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 67:23
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Tidskriftsartikel (refereegranskat)abstract
- Doping crystalline silicon with silver results in a photoluminescence center with multiplet zero-phonon structure near 778.9 meV. We show that the published assignments of the vibronic sidebands are wrong, with severe implications for the relative transition probabilities of the luminescence transitions from the excited states. At low temperature, most of the luminescence intensity derives from the phonon sideband associated with a forbidden zero-phonon line through the phonon-assisted coupling of two of the excited states of the center. The effective mass of the vibration is determined from isotope effects to be close to the mass of one Ag atom. Uniaxial stress and magnetic perturbations establish that the current assignment of the electronic structure of the center is incorrect and that it is best described by a new variant on the "pseudodonor" model. An electron orbits in an effective T-d environment, with an orbital triplet as its lowest-energy state, giving a j=3/2 electron state. A tightly bound hole has its orbital angular momentum quenched by the C-3v symmetry of the center, leaving only spin angular momentum (s=1/2). These particles couple to give J=2,1,0 states. Using this model, the temperature dependence of both the total luminescence intensity and measured radiative decay time can be understood. These data allow an estimate to be made of the thermally induced transition rate of the electron from the effective-mass excited states into the conduction band.
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| 3. |
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| 4. |
- Landin, L., et al.
(författare)
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Interband transitions in InAs quantum dots in InP studied by photoconductivity and photoluminescence techniques
- 2004
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Ingår i: Journal of Applied Physics. - Melville : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 95:12, s. 8007-8010
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed investigation of the interband optics of self-assembled InAs dots embedded in a matrix of InP. In photoconductivity (PC) measurements, we observe optical processes related to the dots and a wetting layer, band-to-band excitation of the InP barrier, as well as to an interesting As-related impurity. In particular, the PC measurements reveal the electronic structure of the dots and strongly suggest that an Auger effect is involved in forming the PC signal. Comparing the PC and photoluminescence (PL) signals, we observe that the fundamental transition is not observed in PC, which we interpret in terms of Pauli blocking due to electrons populating the ground state of the dots. In general, it is demonstrated that the PC technique is in many respects complementary to PL and gives additional insight into the electronic structure of quantum dots.
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| 5. |
- Lindstrom, J.L., et al.
(författare)
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Defect engineering in Czochralski silicon by electron irradiation at different temperatures
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186:1-4, s. 121-125
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Tidskriftsartikel (refereegranskat)abstract
- Infrared absorption studies of defect formation in Czochralski silicon irradiated with fast electrons in a wide range of temperatures (80-900 K) have been performed. The samples with different contents of oxygen (16O,18O) and carbon (12C,13C) isotopes were investigated. The main defect reactions are found to depend strongly on irradiation temperature and dose, as well as on impurity content and pre-history of the samples. Some new radiation-induced defects are revealed after irradiation at elevated temperatures as well as after a two-step (hot+room-temperature (RT)) irradiation. © 2002 Elsevier Science B.V. All rights reserved.
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| 6. |
- Lindström, Lennart, et al.
(författare)
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Carbon-oxygen-related complexes in irradiated and heat-treated silicon : IR absorption studies
- 2002
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Ingår i: Solid State Phenomena. - 1012-0394 .- 1662-9779. ; 82-84, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- Carbon-oxygen-related complexes in Si crystals enriched with either oxygen (O-16,O-18) or carbon (C-12, C-13) isotopes were investigated by Fourier Transform infrared absorption spectroscopy. The samples were irradiated with electrons at room temperature as well as at elevated temperatures (400-600 degreesC). The oxygen isotopic shifts of the local vibrational modes related to C3 and C4 centers were determined. Several new lines were found to appear after irradiation at elevated temperatures. Possible assignments of them are suggested.
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| 7. |
- Markevich, VP, et al.
(författare)
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Stable hydrogen pair trapped at carbon impurities in silicon
- 2003
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Ingår i: Defect and Diffusion Forum. - 1012-0386 .- 1662-9507. ; 221-2, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Local mode spectroscopy and ab initio modeling are used to investigate two trigonal defects found in carbon rich Si into which H had been in-diffused. Isotopic shifts with D and C-13 are reported along with the effect of uniaxial stress. Ab-initio modeling studies suggest that the two defects are two forms of the CH2* complex where one of the two hydrogen atoms lies at an anti-bonding site attached to C or Si respectively. The two structures are nearly degenerate and possess vibrational modes in good agreement with those observed experimentally. The defects are energetically favorable in comparison with separated C-s and H-2 in Si and may represent aggregation sites for hydrogen.
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| 8. |
- Murin, LI, et al.
(författare)
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Spectroscopic observation of the TDD0 in silicon
- 2003
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Ingår i: Physica B: Condensed Matter. - : Elsevier BV. - 0921-4526. ; 340, s. 1046-1050
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Tidskriftsartikel (refereegranskat)abstract
- The electronic transitions of 16 neutral thermal double donors (TDD1-TDD16) and of nine positively charged species (TDD1-TDD9) were observed previously in infrared absorption spectra. An earlier species (TDD0) was detected, however, only in persistent photoconductivity and Hall effect studies. In the present work, lines related to the electronic transitions from the ground to excited states in both neutral and singly ionized charge states of the TDD0 have been identified by infrared absorption and bistability of the defect has been confirmed. (C) 2003 Elsevier B.V. All rights reserved.
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| 9. |
- Pettersson, Håkan, et al.
(författare)
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Intersubband photoconductivity of self-assembled InAs quantum dots embedded in InP
- 2004
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 95:4, s. 1829-1831
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Tidskriftsartikel (refereegranskat)abstract
- The results from photoconductivity (PC) measurements on InAs dots embedded in InP are presented. The PC technique is recently applied to the study of InAs dots embedded in matrices of GaAs and Al0.3Ga0.7As matrix, respectively. It is demonstrated that this technique reveals important new physical insight into the electronic structure of the InAs/InP dots, information that cannot easily be obtained by other techniques.
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| 10. |
- Pettersson, Håkan, et al.
(författare)
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Photocurrent spectroscopy on self-assembled InAs quantum dots embedded in InP
- 2005
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Ingår i: Microelectronics Journal. - Amsterdam : Elsevier. - 0026-2692. ; 36:3-6, s. 227-230
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report on an overview of recent results from Fourier transform photocurrent (FTPC) measurements in the infrared spectral region on ensembles of self-assembled InAs quantum dots embedded in a matrix of InP. In interband PC, clear signals related to the dots are observed. Comparing the PC- and PL spectra, we observe that the fundamental transition is absent in the PC spectra, which we interpret in terms of Pauliblocking due to a filled electron ground state of the dots. Our results furthermore suggest that an Auger process is involved in forming the interband PC signal. In intersubband PC, peaks related to transitions from the dots' ground- and first excited states to the conduction band of the matrix are observed. Using a novel approach of combining FTPC with illumination from an additional external non-modulated light source, we have measured the spectral distribution of photoionization of excitons in quantum dots and found an exciton binding energy in good agreement with theoretical calculations.
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