| 1. |
- Monakhov, E. V., et al.
(författare)
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Formation of a double acceptor center during divacancy annealing in low-doped high-purity oxygenated Si
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:23
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Tidskriftsartikel (refereegranskat)abstract
- Deep-level transient spectroscopy studies of electronic defect levels in 7-MeV proton-irradiated n-type float-zone Si with a doping of (3-5)x10(12) cm(-3) and oxygen content of similar to10(16)-10(17) cm(-3) have been performed. The thermal stability of the irradiation-induced defects has been investigated for temperatures up to 400 degreesC. It has been found that annealing of the divacancy-related levels, the singly negative, V-2(0/-), and the doubly negative, V-2(-/=), charge states at 220-300 degreesC results in the formation of a new center with singly negative, X(0/-), and doubly negative, X(-/=), charge states. The new center anneals out at 325-350 degreesC during isochronal treatment for 15 min. The capture kinetics studies reveal that the electron capture cross section of X(0/-) is larger than that of V-2(0/-) while the capture cross section of X(-/=) is close to that of V-2(-/=). The transformation of V-2(0/-) and V-2(-/=) into X(0/-) and X(-/=) is very efficient with only a small loss in the peak amplitudes, and the position of the energy levels are close to those of V-2. Hence, it is tempting to suggest that the atomic configuration of the X center is closely related to that of V-2, and a possible identification of X may be the divacancy-oxygen center (V2O).
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| 2. |
- Monakhov, E. V., et al.
(författare)
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Laplace transform transient spectroscopy study of a divacancy-related double acceptor centre in Si
- 2003
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 15:39, s. S2771-S2777
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Tidskriftsartikel (refereegranskat)abstract
- Radiation-induced divacancy-related levels in high-purity oxygen-enriched n-type silicon have been studied with the use of deep level transient spectroscopy (DLTS) and Laplace-DLTS. It has been shown that heat treatment at 250degreesC results in a shift of the divacancy (V-2)-related peaks observed by 'standard' DLTS. Using Laplace-DLTS it is demonstrated that the shift is due to annealing of V-2 and formation of a new acceptor centre. The new centre has presumably two negative charge states: singly and doubly negative. The formation of the new centre holds a close one-to-one correlation with the annealing of V-2, indicating that the new centre is a result of divacancy interaction with an impurity or a defect. The close position of the electronic levels of the new centre to that of V-2 suggests a similar electronic and microscopic structure of the new centre to V-2, and a tentative identification is a divacancy-oxygen centre.
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| 3. |
- Svensson, B. G., et al.
(författare)
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Defects and diffusion in high purity silicon for detector applications
- 2004
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Ingår i: Conference on Photo-Responsive Materials, Proceedings. - : Wiley-VCH Verlagsgesellschaft. - 3527405526 ; , s. 2250-2257
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Konferensbidrag (refereegranskat)abstract
- In this contribution we review some recent results on defects occurring after irradiation and thermal treatment of silicon detectors for ionizing radiation. In particular, the annealing of the prominent divacancy centre and the concurrent growth of a new double acceptor centre, assigned to the divacancy-oxygen pair, is treated in detail. The detectors were fabricated using oxygenated high purity float zone (FZ) silicon wafers of n-type in order to improve the radiation hardness. The results obtained have important implication on our current understanding of the degradation of silicon detectors at high radiation fluences and suggest that a new concept for optimised impurity/defect engineering needs to be developed.
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| 4. |
- Aberg, D., et al.
(författare)
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Nitrogen deactivation by implantation-induced defects in 4H-SiC epitaxial layers
- 2001
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:19, s. 2908-2910
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation causes free charge carrier reduction due to damage in the crystalline structure. Here, nitrogen-doped 4H silicon carbide (n type) epitaxial layers have been investigated using low ion doses in order to resolve the initial stage of the charge carrier reduction. It was found that the reduction of free carriers per ion-induced vacancy increases with increasing nitrogen content. Nitrogen is suggested to be deactivated through reaction with migrating point defects, and silicon vacancies or alternatively interstitials are proposed as the most likely candidates.
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| 5. |
- Aberg, D., et al.
(författare)
-
Nitrogen passivation by implantation-induced point defects in 4H-SiC epitaxial layers
- 2001
-
Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 184:04-jan, s. 263-267
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation causes damage to the crystal lattice resulting in the loss of free charge carriers. In this study, low dose implantations using different ions and implantation doses are made to resolve the initial carrier loss in nitrogen-doped epitaxial layers. A strong dependence of compensation on nitrogen concentration is seen, showing that nitrogen is passivated by implantation-induced point defects. An activation energy of 3.2 eV for the dissociation of the passivated nitrogen center is obtained.
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| 6. |
- Ber, B. Y., et al.
(författare)
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Determination of nitrogen in silicon carbide by secondary ion mass spectrometry
- 2004
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Ingår i: Journal of Analytical Chemistry. - 1061-9348 .- 1608-3199. ; 59:3, s. 250-254
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Tidskriftsartikel (refereegranskat)abstract
- The emission of atomic and complex nitrogen ions, which are the main impurity determining the n type conduction of silicon carbide, is investigated. It is shown that, among all the secondary ions of the CxN and SixN kind (x = 0, 1, 2, 3), the (26)(CN)(-) fragment exhibits the highest ion yield. The use of an ion peak with a specified mass as an analytical signal provides a detection limit for nitrogen in SiC at a level of 10(16) cm(-3). This result is attained in measurements at high mass resolution (M/DeltaM = 7500, interference peak (26)(C-13(2))(-)).
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| 7. |
- David, M. L., et al.
(författare)
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Electrically active defects in irradiated 4H-SiC
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 95:9, s. 4728-4733
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Tidskriftsartikel (refereegranskat)abstract
- 4H-SiC epilayers were irradiated with either protons or electrons and electrically active defects were studied by means of deep level transient spectroscopy. Motion of defects has been found to occur at temperature as low as 350-400 K. Indeed, the application of an electric field has been found to enhance modifications in defect concentrations that can also occur during long time annealing at elevated temperature. Two levels have been revealed and labeled B and M. Two other levels, referred to as S-1 and S-2 and located at 0.40 and 0.71 eV below the conduction band edge have been studied in detail (capture cross sections, profiling, formation energy, activation energy during annealing). The S-1 and S-2 levels have been found to exhibit a one to one relation and are proposed to be two charge states of the same acceptor center, labeled the S center.
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| 8. |
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| 9. |
- Haeggstrom, A, et al.
(författare)
-
Nasal mucosal swelling and reactivity during a menstrual cycle
- 2000
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Ingår i: ORL. - : S. Karger AG. - 0301-1569 .- 1423-0275. ; 62:1, s. 39-42
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Tidskriftsartikel (refereegranskat)abstract
- <i>Introduction:</i> Nasal stuffness is a great problem for many women in the later part of pregnancy. <i>Objective:</i> This study was performed to evaluate whether oestrogen causes nasal congestion and/or a hyperreactive reaction of the nasal mucosa. <i>Material and Methods:</i> Ten healthy fertile women were examined during menstruation. Nasal mucosal congestion was studied with rhinostereometry and acoustic rhinometry. The nasal mucosa was challenged with 3 doses of histamine solution to study nasal reactivity. Measurements were made 3 times during menstruation. To find the exact time of ovulation, when oestrogen reaches its peak value, intravaginal ultrasound tests were done and blood samples taken, to determine the oestrogen and progesterone levels. <i>Results:</i> The nasal mucosa became hyperreactive to histamine in connection with ovulation, when the blood level of oestrogen reached its peak. This does not occur during the menstrual or the luteal phase. No significant alteration was found in the baseline position during the menstruation. <i>Conclusion:</i> There is a connection between high oestrogen level and nasal mucosal reactivity.
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| 10. |
- Hallen, A, et al.
(författare)
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Implanted p(+)n-junctions in silicon carbide
- 2003
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Ingår i: APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY. ; , s. 653-657
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Konferensbidrag (refereegranskat)abstract
- Ion implantation is considered a key technology for the realisation of silicon carbide electronic devices. Here we will give an overview of the field and present some recent results of ion implanted 4H SiC epitaxial layers. Mainly Al ions of keV energies have been used at different fluence, flux and target temperature. The samples have been investigated by secondary ion mass spectrometry (SIMS), channeling Rutherford backscattering (RBS-c) and transmission electron microscopy (TEM), both as-implanted and after annealing up to 1900 degreesC. Also the electrical activation of Al-implanted and annealed material has been investigated by scanning spreading resistance microscopy (SSRM). The damage accumulation, monitored by RBS-c, is linear with ion fluence but depends strongly on implantation temperature and ion flux. Annealing at temperatures above 1700 degreesC is needed to remove the damage and to electrically activate implanted Al ions. At these high annealing temperatures, however, dislocation loops are formed that have a negative influence on device performance.
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| 11. |
- Hallén, Anders., et al.
(författare)
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Ion implantation of silicon carbide
- 2002
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 186-194
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation is an important technique for a successful implementation of commercial SiC devices. Much effort has also been devoted to optimising implantation and annealing parameters to improve the electrical device characteristics. However, there is a severe lack of understanding of the fundamental implantation process and the generation and annealing kinetics of point defects and defect complexes. Only very few of the most elementary intrinsic point defects have been unambiguously identified so far. To reach a deeper understanding of the basic mechanisms SiC samples have been implanted with a broad range of ions, energies, doses, etc., and the resulting defects and damage produced in the lattice have been studied with a multitude of characterisation techniques. In this contribution we will review some of the results generated recently and also try to indicate where more research is needed. In particular, deep level transient spectroscopy (DLTS) has been used to investigate point defects at very low doses and transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) are used for studying the damage build-up at high doses.
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| 12. |
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| 13. |
- Ivanov, A M, et al.
(författare)
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High-resolution short range ion detectors based on 4H-SiC films
- 2004
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Ingår i: Technical physics letters. - : Pleiades Publishing Ltd. - 1063-7850 .- 1090-6533. ; 30:7, s. 575-577
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Tidskriftsartikel (refereegranskat)abstract
- The energy resolution of SiC detectors has been studied in application to the spectrometry of alpha particles with 5.1-5.5 MeV energies. The Schottky barrier structure of the detector was based on a CVD-grown epitaxial n-4H-SiC film with a thickness of 26 mum and an uncompensated donor concentration of (1-2) x 10(15) cm(-3). An energy resolution of 0.5% achieved for the first time with SiC detectors allows fine structure of the alpha particle spectrum to be revealed. The average energy of the electron-hole pair formation in 4H-SiC is estimated at 7.71 eV.
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| 14. |
- Janson, M S, et al.
(författare)
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Channeled implants in 6H silicon carbide
- 2000
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS - 1999 PTS, 1 & 2. ; , s. 889-892
-
Konferensbidrag (refereegranskat)abstract
- Implants of MeV B-11, Al-27 and Ga-69 into the <0001> channel of 6H-SiC have been performed and concentration versus depth profiles have been obtained utilizing secondary ion mass spectrometry (SIMS). The experiment shows that the deepest channeled Ga ions reach a depth of 6.6 mum, which is 4 times deeper than the projected range of a random angle implantation, while the deepest channeled B ions only exceed the random projected range by 40%. Measurements at several implantation fluences show that implantation induced damage quench the deep channeling at fluences around 2 and 10x10(13) cm(-2) for Al and Ga, respectively, while only a minor fluence dependence is found in the B implants at fluences up to 2.6x10(14) cm(-2). The ion mass dependence of these effects is explained by the electronic to nuclear stopping ratios. Monte Carlo simulations of the channeling implants have also been performed and good agreements are found between simulations and experimental data.
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| 15. |
- Janson, M S, et al.
(författare)
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Diffusion of dopants and impurities in device structures of SiC, SiGe and Si
- 2001
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Ingår i: DIFFUSIONS IN MATERIALS. ; , s. 597-609
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Konferensbidrag (refereegranskat)abstract
- Silicon Carbide (SiC) has a high thermal stability and for most elements temperatures in excess of 2000 degreesC are anticipated to reach reasonable diffusivities (greater than or equal to 10(-13) cm(2)/s). We demonstrate, however, that light elements, like hydrogen and lithium, exhibit a considerable mobility already at less than or equal to 400 degreesC, Technologically, the principal interest in these light elements arises because of their ability to electrically passivate shallow acceptors and donors as well as deep level defects in common semiconductors (SiC, Si, GaAs). Indeed, for both hydrogen and lithium the diffusion kinetics is shown to be strongly affected by trapping and de-trapping at boron impurities in the SiC layers. Evidence is also provided that hydrogen migrates as a positively charged ion in p-type SiC. Furthermore, similar to that in crystalline silicon, transient enhanced diffusion of ion-implanted boron is observed in SiC. The initial boron diffusivity during postimplant annealing at 1600 degreesC is enhanced by more than two orders of magnitude compared to equilibrium conditions. For Silicon Germanium (SiGe) diffusion of the n-type dopants Sb and P is studied. Comparing results from strained and relaxed SiGe layers annealed under inert and oxidizing conditions it is unambiguously shown that the diffusion of Sb is almost exclusively mediated by vacancies. On the other hand, P diffusion is predominantly assisted by Si self-interstitials and in this case compositional and strain effects in the SiGe layers are competing.
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| 16. |
- Janson, M S, et al.
(författare)
-
Dissociation energy of the passivating hydrogen-aluminum complex in 4H-SiC
- 2001
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Ingår i: Materials Science Forum. ; , s. 427-430
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The thermal stability of the passivating hydrogen-aluminum complex ((HAl)-H-2) in 4H-silicon carbide has been studied by determining the effective diffusion constant for hydrogen in an AI-doped epitaxial layer. Assuming a complex comprised of one H-2 and one AI acceptor ion, the extracted diffusivities provide the dissociation frequency of the complex. The extracted frequencies cover three orders of magnitude and yield a close to perfect fit to an Arrhenius equation with the extracted dissociation energy for the (HAl)-H-2-complex equal to 1.66 (+/-0.05) eV and a pre-exponential attempt frequency nu (0) = 1.7x10(13) s(-1) in good agreement with the expected value for a first order dissociation process.
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| 17. |
- Janson, M. S., et al.
(författare)
-
Hydrogen-boron complex formation and dissociation in 4H-silicon carbide
- 2001
-
Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 184:04-jan, s. 257-262
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Tidskriftsartikel (refereegranskat)abstract
- The diffusion of deuterium (H-2) in p-type 4H-silicon carbide (SiC) has been studied in detail by secondary ion mass spectrometry. An effective capture radius for the formation of H-2-B complexes at 460 degreesC is determined to R-HB = (21 +/- 4) A. This value is in good agreement with that expected for a coulomb force-assisted trapping mechanism. At higher temperatures, the H-2 diffusion follows Fick's law with a constant effective diffusivity from which the complex dissociation frequencies nu (HB) are determined. The frequencies exhibit an Arrhenius temperature dependence over the three orders of magnitude covered by the extracted nu (HB). The complex dissociation energy is determined to E-d(HB) = (2.51 +/- 0.04) eV which is 0.9 eV larger than the corresponding value for the H-2-Al complex, suggesting that the atomic configurations for the two complexes are significantly different. The extracted dissociation attempt frequency, nu (HB)(0) = (1.2 +/- 0.7) x 10(13) s(-1) is very close to the characteristic oscillation frequency of the SiC lattice, nu (SiC)(lattice) = 1.6 x 10(13) s(-1). In addition, H-2 diffusion in an epitaxial AI multilayer structure demonstrates the influence of internal electric fields on the H-2 diffusion in p-type SiC.
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| 18. |
- Janson, M. S., et al.
(författare)
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Hydrogen diffusion, complex formation, and dissociation in acceptor-doped silicon carbide
- 2001
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 64:19
-
Tidskriftsartikel (refereegranskat)abstract
- The diffusion of deuterium (H-2) in B and Al doped 4H and 6H silicon carbide (SiC) has been studied in detail by secondary ion mass spectrometry. From H-2 depth profiles, following trap limited diffusion with negligible complex dissociation, an effective capture radius for the formation of H-2-B complexes (at 460 degreesC) is determined to R-HB = (21+/-4) Angstrom. This value is in good agreement with that expected for a Coulomb force assisted trapping mechanism. At annealing conditions where dissociation is non-negligible, the H-2 diffusion follows Fick's law with a constant effective diffusivity, from which the complex dissociation frequencies nu are determined. The extracted values of nu cover three orders of magnitude and exhibit a close to perfect Arrhenius temperature dependence for both H-2-B and H-2-Al complexes. The large difference between the extracted complex dissociation energies, E-d(HB)=(2.51+/-0.04) eV and E-d(HA1)=(1.61+/-0.02) eV, suggests that the atomic configurations of the two complexes are significantly different. The corresponding extracted dissociation attempt frequencies, nu (HB)(0)=(1.2+/-0.7) x 10(13) s(-1) and nu (HA1)(0)=(0.7+/-0.3) x 10(13) s(-1), are very close to the characteristic oscillation frequency of the SiC lattice, nu (SiC)(lattice)=1.6 x 10(13) s(-1). This is strong evidence for the assumption of a first order dissociation process. No difference between 4H- and 6H-SiC has been observed.
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| 19. |
- Janson, M. S., et al.
(författare)
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Ion implantation range distributions in silicon carbide
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:11, s. 8903-8909
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Tidskriftsartikel (refereegranskat)abstract
- The first to fourth order distribution moments, R-p, DeltaR(p), gamma, and beta, of 152 single energy H-1, H-2, Li-7, B-11, N-14, O-16, Al-27, P-31, Ga-69, and As-75 implantations into silicon carbide (SiC) have been assembled. Fifty of these implantations have been performed and analyzed in the present study while the remaining mplantation data was compiled from the literature. For ions with a limited amount of experimental data, additional implantations were simulated using a recently developed binary collision approximation code for crystalline materials. Least squares fits of analytical functions to the distribution moments versus implantation energy provide the base for an empirical ion implantation simulator using Pearson frequency functions.
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| 20. |
- Janson, M S, et al.
(författare)
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Range distributions of implanted ions in silicon carbide
- 2002
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2001, PTS 1 AND 2, PROCEEDINGS. ; , s. 779-782
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Konferensbidrag (refereegranskat)abstract
- The first four distribution moments (R-P, DeltaR(p), gamma and beta) of 113 experimental single energy ion implantations into silicon carbide (SiC) have been assembled to form the base for an empirical ion implantation simulator using Pearson frequency functions. The studied ions are H-1, H-2, Li-7, B-11, N-14, O-11, Al-27, P-31, and As-75, and the implantation energies range from 0.5 keV to 4 MeV. Thirty-nine of these implantations have been implanted, measured, and analyzed in the present study while the remaining implantation data were gathered from the literature. Furthermore, 16 additional implantations were simulated - using a new Binary Collision Approximation (BCA) code for crystalline materials - to fill up the missing energies for ions with limited experimental data. The extracted range data are presented as tabulated fitting constants to analytical functions of the distribution moments versus implantation energy.
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| 21. |
- Janson, M. S., et al.
(författare)
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Transient enhanced diffusion of implanted boron in 4H-silicon carbide
- 2000
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:11, s. 1434-1436
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Tidskriftsartikel (refereegranskat)abstract
- Experimental evidence is given for transient enhanced diffusion of boron (B) in ion-implanted silicon carbide (SiC). The implanted B is diffusing several mu m into the samples when annealed at 1600 and 1700 degrees C for 10 min, but the in-diffused tails remain unaffected when the annealing times are increased to 30 min at the same temperatures. A lower limit of the effective B diffusivity at 1600 degrees C is determined to 7x10(-12) cm(2)/s, which is 160 times larger than the equilibrium B diffusivity given in the literature.
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| 22. |
- Kuznetsov, A. Y., et al.
(författare)
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Dynamic annealing in ion implanted SiC : Flux versus temperature dependence
- 2003
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 94:11, s. 7112-7115
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Tidskriftsartikel (refereegranskat)abstract
- A strong influence of ion implantation flux on the accumulation of radiation damage, the so-called dose rate effect, is observed and systematically studied in SiC. 100 keV Si+ ions were implanted into bulk 4H-SiC wafers using different ion fluxes (1.9x10(10)-4.9x10(13) ions/cm(2) s) and keeping the implantation dose constant at 5x10(14) Si+/cm(2). The implants were performed both at room and elevated temperatures, up to 220 degreesC. Rutherford backscattering spectrometry in the channelling mode using 2 MeV He+ ions was employed to measure ion implantation damage profiles in the samples. For the flux interval used the most, pronounced dynamic annealing effect was detected at 80-160degreesC, having an activation energy of 1.3 eV. For example, at 100degreesC the amount of disordered Si atoms at the projected ion range is reduced by a factor of 4 by decreasing the ion flux from 4.9x10(13) to 1.9x10(10) ions/cm(2) s. The results are discussed in terms of migration and annihilation of intrinsic type defects for both the Si- and C-sublattices. In addition, two regions for the damage accumulation - at the surface and at the damage peak for 100 keV Si+ ions - are observed.
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| 23. |
- Kuznetsov, A. Y., et al.
(författare)
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Self-interstitial migration during ion irradiation of boron delta-doped silicon
- 2000
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Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 3:4, s. 279-283
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Tidskriftsartikel (refereegranskat)abstract
- Boron delta layers in silicon, grown by molecular beam epitaxy and characterized by the secondary ion mass spectrometry, have been employed to investigate the migration of silicon self-interstitials during irradiation with MeV protons in the 500-850 degreesC temperature range. After growth, the samples were thinned from the backside to a thickness that made them transparent for the proton energies used. As a result, the generation rate of point defects can be considered as essentially uniform throughout the samples. However: the evolution of the boron profiles is almost identical to that observed after injection of self-interstitials caused by thermal oxidation of the samples at elevated temperature. This strongly indicates that the surface acts as a reflective boundary for the migrating self-interstitials or/ and an efficient sink for mobile vacancies. Furthermore, higher value of interstitial supersaturation in the near-surface region in proton-irradiated samples is consistent with experimentally detected depth dependence for immobile fraction in boron clusters. Then, activation energy of boron mobilization, (0.9 +/- 0.4) eV, was attributed to the dissociation of boron clusters.
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| 24. |
- Leveque, P., et al.
(författare)
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Dose-rate influence on the defect production in MeV proton-implanted float-zone and epitaxial n-type silicon
- 2002
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 375-379
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Tidskriftsartikel (refereegranskat)abstract
- The production of stable vacancy-related point defects in proton-implanted float-zone and epitaxial silicon has been studied in the low dose range ( less than or equal to 10(10)/cm(2)) as a function of dose-rate. The well-known inverse dose-rate effect has been observed in both types of materials with a decrease in the concentration of vacancy-related defects as the dose-rate increases. The effect is less pronounced in oxygen lean epitaxial silicon. Moreover, a continuous decrease of the vacancy-related defect concentration as a function of the flux was measured while a threshold was expected according to previous studies. Both or these results can be explained by a simple calculation, taking into account the influence of the oxygen concentration as well as the influence of the diffusion coefficient of point defects on the inverse dose-rate effect.
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| 25. |
- Leveque, P., et al.
(författare)
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Hydrogen-related defect centers in float-zone and epitaxial n-type proton implanted silicon
- 2001
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 174:3, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen-related defects in float zone (Fz) and epitaxial (Epi) n-type silicon crystals have been studied by means of deep level transient spectroscopy. These defects, as well as the characteristic vacancy-oxygen (VO) and divacancy (V-2) centers were introduced by proton implantation (1.3 MeV) using a dose of 1 x 10(10)/cm(2). A hydrogen-related defect level located at 0.45 eV below the conduction band edge (E-c) appears in both kind of samples. Another hydrogen-related defect appears predominantly in the Fz samples with a level at E-c - 0.32 eV. Depth profiling as well as annealing studies strongly suggest that the level at E-c - 0.45 eV is due to a complex involving hydrogen and V2 The level at E-c - 0.32 eV is strongly suppressed in the high purity Epi samples and the same holds for VO center. These results together with annealing data provide substantial evidence that the E-c - 0.32 eV level originates from a VO-center partly saturated with hydrogen (a VOH complex). Finally, in the Epi samples a new level at similar toE(c) - 0.31 eV is resolved, which exhibits a concentration Versus depth profile strongly confined to the damage peak region. The origin of this level is not known but the extremely narrow depth profile may indicate a higher-order defect of either vacancy or interstitial type,
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| 26. |
- Leveque, P., et al.
(författare)
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Identification of hydrogen related defects in proton implanted float-zone silicon
- 2003
-
Ingår i: European Physical Journal. - : EDP Sciences. - 1286-0042 .- 1286-0050. ; 23:1, s. 5-9
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen related defects in high purity n-type float zone silicon samples have been studied by means of Deep Level Transient Spectroscopy. They were introduced, as well as the characteristic vacancy-oxygen (VO) and divacancy (V-2) centers, by MeV proton implantation. Two hydrogen related defect levels were resolved at 0.32 eV and 0.45 eV below the conduction band edge (E-c). Careful annealing studies indicate strongly that a third hydrogen related level, overlapping with the singly negative charge state level of V-2, is also present in the implanted samples. The annealing behavior of the hydrogen related defects has been compared with literature data leading to a rather firm identification. The E-c-0.32 eV level originates from a VO center partly saturated with hydrogen (a VOH complex) while the E-c-0.45 eV level may be ascribed to a complex involving a monovacancy and a hydrogen atom ( a VH complex). The third hydrogen related defect is tentatively ascribed to a complex involving a hydrogen atom and a divacancy ( a V2H complex).
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| 27. |
- Leveque, Patrick, et al.
(författare)
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Vacancy and interstitial depth profiles in ion-implanted silicon.
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:2, s. 871-877
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Tidskriftsartikel (refereegranskat)abstract
- An experimental method of studying shifts between concentration-versus-depth profiles of vacancy- and interstitial-type defects in ion-implanted silicon is demonstrated. The concept is based on deep level transient spectroscopy measurements utilizing the filling pulse variation technique. The vacancy profile, represented by the vacancy-oxygen center, and the interstitial profile, represented by the interstitial carbon-substitutional carbon pair, are obtained at the same sample temperature by varying the duration of the filling pulse. The effect of the capture in the Debye tail has been extensively studied and taken into account. Thus, the two profiles can be recorded with a high relative depth resolution. Using low doses, point defects have been introduced in lightly doped float zone n-type silicon by implantation with 6.8 MeV boron ions and 680 keV and 1.3 MeV protons at room temperature. The effect of the angle of ion incidence has also been investigated. For all implantation conditions the peak of the interstitial profile is displaced towards larger depths compared to that of the vacancy profile. The amplitude of this displacement increases as the width of the initial point defect distribution increases. This behavior is explained by a simple model where the preferential forward momentum of recoiling silicon atoms and the highly efficient direct recombination of primary point defects are taken into account.
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| 28. |
- Martin, David M., et al.
(författare)
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Bistable defect in mega-electron-volt proton implanted 4H silicon carbide
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:10, s. 1704-1706
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial 4H-SiC n-type layers implanted at room temperature with a low fluence of mega-electron-volt protons have been measured by deep level transient spectroscopy (DLTS). The proton fluence of 1x10(12) cm(-2) creates an estimated initial concentration of intrinsic point defects of about 10(14) cm(-3) of which about 10% remain after the implantation and gives rise to deep states in the upper part of the band gap. Here, we investigate the samples prior to high-temperature annealing and a very complex spectrum is revealed. In particular, a bistable defect M is discovered having two DLTS peaks, M-1 and M-3 at E-C-0.42 and around E-C-0.75 eV, respectively, in one configuration and one peak, M-2 at E-C-0.70 eV in the other configuration. The charge dependent thermal activation energies for the transformation between the bistable defect peaks are 0.90 and 1.40 eV.
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| 29. |
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| 30. |
- Pellegrino, P., et al.
(författare)
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Annealing kinetics of vacancy-related defects in low-dose MeV self-ion-implanted n-type silicon
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 64:19
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Tidskriftsartikel (refereegranskat)abstract
- Silicon samples of n-type have been implanted at room temperature with 5.6-MeV Si-28 ions to a dose of 2 x 10(8) cm(-2) and then annealed at temperatures from 100 to 380 degreesC. Both isothermal and isochronal treatments were performed and the annealing kinetics of the prominent divacancy (V-2) and vacancy-oxygen (VO) centers were studied in detail using deep-level transient spectroscopy. The decrease Of V2 centers exhibits first-order kinetics in both Czochralski-grown (CZ) and float-zone (FZ) samples, and the data provide strong evidence for a process involving migration of V-2 and subsequent annihilation at trapping centers. The migration energy extracted for V-2 is similar to1.3 eV and from the shape of the concentration versus depth profiles, an effective diffusion length less than or equal to0.1 mum is obtained. The VO center displays a more complex annealing behavior where interaction with mobile hydrogen (H) plays a key role through the formation of VOH and VOH2 centers. Another contribution is migration of VO and trapping by interstitial oxygen atoms in the silicon lattice, giving rise to vacancy-dioxygen pairs. An activation energy of similar to 1.8 eV is deduced for the migration of VO, in close resemblance with results from previous studies using electron-irradiated samples. A model for the annealing of VO, involving only three reactions, is put forward and shown to yield a close quantitative agreement with the experimental data for both CZ and FZ samples over the whole temperature range studied.
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| 31. |
- Pellegrino, P., et al.
(författare)
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Separation of vacancy and interstitial depth profiles in proton- and boron-implanted silicon
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 334-338
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Tidskriftsartikel (refereegranskat)abstract
- A new experimental method of studying shifts between concentration-versus-depth profiles of vacancy-type and interstitial-type defects in ion-implanted silicon is demonstrated. The concept is based on deep level transient spectroscopy (DLTS) measurements utilizing the filling pulse variation technique. The vacancy profile. represented by the vacancy-oxygen center and the interstitial profile, represented by the substitutional carbon-interstitial carbon pair, are obtained at the same sample temperature by varying the duration of the filling pulse, Thus the two profiles can be recorded with a high relative depth resolution, Point defects have been introduced in low doped float zone n-type silicon by implantation with 6 MeV boron ions and 1.3 MeV protons at room temperature, using low doses. For each implantation condition the peak of the interstitial profile is shown to be displaced by similar to 0.5 mum towards larger depths compared to that of the vacancy profile. This shift is primarily attributed to the preferential forward momentum of recoiling Si atoms, in accordance with theoretical predictions.
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