| 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. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Optical and electrical characterization of (Ga,Mn)N/InGaN multiquantum well light-emitting diodes
- 2004
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 33:5, s. 467-471
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Tidskriftsartikel (refereegranskat)abstract
- (Ga,Mn)/N/InGaN multiquantum well (MQW) diodes were grown by molecular beam epitaxy (MBE). The current-voltage characteristics of the diodes show the presence of a parasitic junction between the (Ga,Mn)N and the n-GaN in the top contact layer due to the low conductivity of the former layer. Both the (Ga,Mn)N/InGaN diodes and control samples without Mn doping show no or very low (up to 10% at the lowest temperatures) optical (spin) polarization at zero field or 5 T, respectively. The observed polarization is shown to correspond to the intrinsic optical polarization of the InGaN MQW, due to population distribution between spin sublevels at low temperature, as separately studied by resonant optical excitation with a photon energy lower than the bandgap of both the GaN and (Ga,Mn)N. This indicates efficient losses in the studied structures of any spin polarization generated by optical spin orientation or electrical spin injection. The observed vanishing spin injection efficiency of the spin light-emitting diode (LED) is tentatively attributed to spin losses during the energy relaxation process to the ground state of the excitons giving rise to the light emission.
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| 3. |
- Storasta, Liutauras, et al.
(författare)
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Deep levels created by low energy electron Irradiation in 4H-SiC
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:9, s. 4909-4915
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Tidskriftsartikel (refereegranskat)abstract
- With low energy electron irradiation in the 80-250 keV range, we were able to create only those intrinsic defects related to the initial displacements of carbon atoms in the silicon carbide lattice. Radiation induced majority and minority carrier traps were analyzed using capacitance transient techniques. Four electron traps (EH1, Z1/Z2, EH3, and EH7) and one hole trap (HS2) were detected in the measured temperature range. Their concentrations show linear increase with the irradiation dose, indicating that no divacancies or di-interstitials are generated. None of the observed defects was found to be an intrinsic defect-impurity complex. The energy dependence of the defect introduction rates and annealing behavior are presented and possible microscopic models for the defects are discussed. No further defects were detected for electron energies above the previously assigned threshold for the displacement of the silicon atom at 250 keV. © 2004 American Institute of Physics. 10.1063/1.1778819.
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| 4. |
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| 5. |
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| 6. |
- Forsberg, Urban, 1971-, et al.
(författare)
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Growth and characterisation 4H-SiC MESFET structures grown by Hot-Wall CVD
- 2001
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Ingår i: Proc. of the MRS 2000 Fall Meeting. ; , s. H2.3.2-
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Konferensbidrag (refereegranskat)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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| 7. |
- Forsberg, U., et al.
(författare)
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Growth and characterisation of 4H-SiC MESFET structures grown by hot-wall CVD
- 2001
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Ingår i: Materials Research Society Symposium - Proceedings. - Boston, MA. ; , s. H2.3.1-H2.3.6
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Konferensbidrag (refereegranskat)abstract
- Metal semiconductor field effect transistor, MESFET, structures have been grown in a hot-wall CVD reactor. Using trimethylaluminium and nitrogen as dopant sources, p- and n-type epitaxial layers were grown on semi insulating substrates. A comprehensive characterization study of thickness and doping of these structures has been performed by using scanning electron microscopy, secondary ion mass spectrometry, capacitance-voltage measurements. Each technique is discussed concerning its advantage and disadvantage. Some transistor properties of MESFETs processed on the grown material are presented.
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| 8. |
- Ivanov, Ivan Gueorguiev, et al.
(författare)
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Photoconductivity of lightly-doped and semi-insulating 4H-SiC and the free exciton binding energy
- 2002
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Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 613-616
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Konferensbidrag (refereegranskat)abstract
- The paper presents a study of the structure of the photoconductivity spectra of various 4H-SiC samples near the absorption edge. By means of comparison of the spectra of low doped (mid 10(14) cm(-3)), very low doped (in 10(13) cm(-3) range), and semi-insulating moderately doped samples, features in the photocurrent due to contribution from creation of free carriers (i.e., excitons in the continuum) can be recognised. This is used for determination of the free exciton binding energy, 20.5 +/- 1 meV, in agreement with a previous study. The second lowest conduction band and the spin-orbit split off valence band are also detected.
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| 9. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
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Characteristics of boron in 4H-SiC layers produced by high-temperature techniques
- 2002
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Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 259-262
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Konferensbidrag (refereegranskat)abstract
- Characteristics of boron in as-grown 4H-SiC layers produced by fast epitaxy, i.e. sublimation and vertical hot-wall CVD, were studied by electrical and optical measurements. The boron-related contribution to the net acceptor concentration in the layers (as determined by CV on p-type residual doped sublimation epitaxy layers), the presence of deep boron centers (as indicated by DLTS) and boron-related "green" emission at similar to 505 nm (as observed by CL) are detected for various growth temperatures and C/Si ratios. The results are discussed in relation with the C vacancies in the lattice that may be affected by growth rate and input C/Si ratio in the CVD process.
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| 10. |
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| 11. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Electronic structure of deep defects in SiC
- 2004
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Ingår i: Silicon Carbide: Recent Major Advances. - Berlin, Heidelberg : Springer Verlag. - 9783540404583 - 3540404589 ; , s. -899
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Since the 1997 publication of Silicon Carbide - A Review of Fundamental Questions and Applications to Current Device Technology edited by Choyke, et al., there has been impressive progress in both the fundamental and developmental aspects of the SiC field. So there is a growing need to update the scientific community on the important events in research and development since then. The editors have again gathered an outstanding team of the world's leading SiC researchers and design engineers to write on the most recent developments in SiC. The book is divided into five main categories: theory, crystal growth, characterization, processing and devices. Every attempt has been made to make the articles as up-to-date as possible and assure the highest standards of accuracy. As was the case for earlier SiC books, many of the articles will be relevant a decade from now so that this book will take its place next to the earlier work as a permanent and essential reference volume.
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| 12. |
- Storasta, L, et al.
(författare)
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Correlation between electrical and optical mapping of boron related complexes in 4H-SiC
- 2002
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS - 2002. ; , s. 423-426
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Konferensbidrag (refereegranskat)abstract
- Boron related photoluminescence (PL) and capacitance transient spectroscopy (DLTS and MCTS) peaks have been investigated around SIMS craters. Enhancement of boron and hydrogen related PL was observed in the vicinity of the crater, whereas the concentration of electrically active boron as measured by MCTS has decreased considerably. Comparison of the boron MCTS peak behavior after electron and proton irradiation is presented. Possible defect models based on the obtained results are discussed.
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| 13. |
- Svensson, BG, et al.
(författare)
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Doping of silicon carbide by ion implantation
- 2001
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Ingår i: Materials Science Forum, Vols. 353-356. - : Trans Tech Publications Inc.. - 9780878498734 - 0878498737 ; , s. 549-554, s. 549-554
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Konferensbidrag (refereegranskat)abstract
- A brief survey is given of some recent results on doping of 4H- and 6H-SiC by ion implantation. The doses and energies used are between 10(9) and 10(15) cm(-2) and 100 keV and 5 MeV, respectively, and B and Al ions (p-type dopants) are predominantly studied. After low dose implantation (less than or equal to 10(10) cm(-2)) a strong compensation is observed in n-type samples and this holds irrespective of implantation temperature up to 600 degreesC. However, at higher doses (10(14)-10(15) Al/cm(2)) the rate of defect recombination (annihilation) increases substantially during hot implants (greater than or equal to 200 degreesC) and in these samples one type of structural defect dominates after past-implant annealing at 1700-2000 degreesC. The defect is identified as a dislocation loop composed of clustered interstitial atoms inserted on the basal plane in the hexagonal crystal structure. Finally, transient enhanced diffusion (TED) of ion-implanted boron in 4H-samples is discussed.
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| 14. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Impact of extended defects on Hall and magnetoresistivity effects in cubic silicon carbide
- 2012
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Ingår i: Journal of Physics D. - : Institute of Physics (IOP). - 0022-3727 .- 1361-6463. ; 45:22, s. 225102-
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Tidskriftsartikel (refereegranskat)abstract
- From magnetoresistivity effect measurements the carrier mobility at room- temperature is 200 cm2/Vs in heteroepitaxially grown 3C-SiC on 6H-SiC by sublimation epitaxy. The main scattering mechanisms are found to be scattering by neutral impurities at low temperature and by phonons at higher temperature. The carrier concentration is in the range of 1016 cm-3, which corresponds to the concentration of residual doping by nitrogen acquired from photoluminescence measurements. Using magnetoresistance and Hall mobility data we have created a simple model which quantifies the volume of the samples influenced by extended defects. A higher doping near extended defects is either not present in the samples or might be screened by the electrostatic field created by these defects.
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| 15. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Influence of twin boundary orientation on magnetoresistivity effect in free standing 3C–SiC
- 2012
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 74, s. 203-205
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Tidskriftsartikel (refereegranskat)abstract
- Free standing 3C–SiC (111) samples with differently oriented twin boundaries were prepared using on-axis and slightly off-axis 6H–SiC substrates. The orientation of twin boundaries causes either an enhancement or suppression of the magnetoresistance mobility. The origin of carrier mobility difference is attributed to the specific structure of these defects. The height of the barriers created by twin boundaries was found to be 0.2 eV.
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| 16. |
- Zhang, J., et al.
(författare)
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Electrically active defects in n-type 4H-silicon carbide grown in a vertical hot-wall reactor
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:8, s. 4708-4714
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Tidskriftsartikel (refereegranskat)abstract
- The intrinsic and impurity related defects in silicon carbide (SiC), grown in a vertical hot wall reactor using chemical vapor deposition, were discussed. Low concentrations of hole traps and electron traps were detected using capacitance transient techniques. The correlation with the carrier lifetime of the investigated epilayers showed that the Z1/2 and EH6/7 centers are the limiting defects.
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