| 1. |
- Galeckas, Augustinas, et al.
(författare)
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Investigation of stacking fault formation in hydrogen bombarded 4H-SiC
- 2005
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2004. - 0878499636 ; , s. 327-330
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Konferensbidrag (refereegranskat)abstract
- The effects of hydrogen and proton irradiation on stacking fault formation in 4H-SiC are investigated by an optical pump-probe method of imaging spectroscopy. We report optically stimulated nucleation and expansion of stacking faults (SFs) in 0.6 keV H-2(+) implanted n-/n+ and p+/n-/n+ structures. The activation enthalpy for recombination enhanced dislocation glide (REDG) in hydrogenated samples (∼ 0.25 eV) is found to be similar to that in a virgin material. Our results indicate that SFs mainly nucleate at the internal n-/n+ interface, beyond reach of hydrogen, thus justifying minor SF passivation effect. No REDG could be initiated optically in 2.5 MeV proton irradiated samples due to radiation defects providing alternative recombination channels to bypass the REDG mechanism. The radiation damage was verified by DLTS, revealing several new levels below E-C in the range 0.4-0.80 eV, and by PL, showing the onset of D-center related luminescence band and concurrent increase of the nonradiative recombination rate.
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| 2. |
- Kortegaard Nielsen, Hanne, et al.
(författare)
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Annealing study of a bistable defect in proton-implanted n-type 4H-SiC
- 2003
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 340, s. 743-747
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Tidskriftsartikel (refereegranskat)abstract
- The thermal stability and annealing kinetics of a bistable defect, recently reported by Martin (Master Thesis, KTH/ELE/FTE/2003-1) employing deep level transient spectroscopy and labelled the M-centre, has been studied using n-type epitaxially grown 4H-SiC layers implanted with 2.5 MeV protons to a dose of 1 X 10(12) cm(-2). One configuration of the bistable defect leads to two levels in the band gap, 0.42 eV (M-1) and 0.7-0.8 eV (M-3) below the conduction band edge (E-C), and another leads to one level (M-2) at E-C-0.7 eV. The defect can be switched back and forth between the two configurations by varying the applied bias and the sample temperature. Isochronal and isothermal annealing shows that the defect anneals out between 310 degrees C and 370 degrees C with a first-order kinetics process. The origin of the defect is not known but it is implantation-induced and a low-order complex.
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| 3. |
- Kortegaard Nielsen, Hanne
(författare)
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Capacitance transient measurements on point defects in silicon and silicol carbide
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrically active point defects in semiconductor materials are important because they strongly affect material properties like effective doping concentration and charge carrier lifetimes. This thesis presents results on point defects introduced by ion implantation in silicon and silicon carbide. The defects have mainly been studied by deep level transient spectroscopy (DLTS) which is a quantitative, electrical characterization method highly suitable for point defect studies. The method is based on measurements of capacitance transients and both standard DLTS and new applications of the technique have been used. In silicon, a fundamental understanding of diffusion phenomena, like room-temperature migration of point defects and transient enhanced diffusion (TED), is still incomplete. This thesis presents new results which brings this understanding a step closer. In the implantation-based experimental method used to measure point defect migration at room temperature, it has been difficult to separate the effects of defect migration and ion channeling. For various reasons, the effect of channeling has so far been disregarded in this type of experiments. Here, a very simple method to assess the amount of channeling is presented, and it is shown that channeling dominates in our experiments. It is therefore recommended that this simple test for channeling is included in all such experiments. This thesis also contains a detailed experimental study on the defect distributions of vacancy and interstitial related damage in ion implanted silicon. Experiments show that interstitial related damage is positioned deeper (0.4 um or more) than vacancy related damage. A physical model to explain this is presented. This study is important to the future modeling of transient enhanced diffusion. Furthermore, the point defect evolution in low-fluence implanted 4H-SiC is investigated, and a large number of new defect levels has been observed. Many of these levels change or anneal out at temperatures below 300 C, which is not in accordance with the general belief that point defect diffusion in SiC requires high temperatures. This thesis also includes an extensive study on a metastable defect which we have observed for the first time and labeled the M-center. The defect is characterized with respect to DLTS signatures, reconfiguration barriers, kinetics and temperature interval for annealing, carrier capture cross sections, and charge state identification. A detailed configuration diagram for the M-center is presented.
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| 4. |
- Kortegaard Nielsen, Hanne, et al.
(författare)
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Capacitance transient study of the metastable M center in n-type 4H-SiC.
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 72:8
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Tidskriftsartikel (refereegranskat)abstract
- The metastable M center in n-type 4H silicon carbide is studied in detail after it has been introduced by 2.5 MeV proton irradiation with a fluence of 1x10(12) cm(-2). The experimental procedures included deep-level transient spectroscopy, carrier capture coefficient and capacitance versus temperature measurements, and pulse-train measurements. The pulse-train measurements are reproduced by simulations. Three band-gap levels have previously been assigned to the M center: M-1 at E-C-0.42 eV, M-2 at E-C-0.63 eV, and M-3 at E-C-0.83 eV, where E-C is the conduction-band edge. Direct measurements of the majority-carrier capture cross sections show that the cross section values extracted from Arrhenius plots are about two orders of magnitude too large, indicating a large entropy factor. A detailed configuration diagram of the M center is presented, including charge state levels and reconfiguration barriers. Evidence in support of a fourth M center level, not explicitly observed, is presented. Isochronal and isothermal annealing experiments show that the M center anneal out between 310 and 370 degrees C in a process displaying first-order kinetics. The annealing process, which is shown to have an activation energy of 2.0 eV, is identified as dissociation.
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| 5. |
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| 6. |
- Kortegaard Nielsen, Hanne, et al.
(författare)
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Electrically active defects in silicon produced by ion channeling
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:22, s. 3865-3867
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Tidskriftsartikel (refereegranskat)abstract
- Low-dose implantations with 65 Si and 150 keV Ge ions into the n(+) top layer of Si n(+)p diodes have been carried out. The defects produced in deeper-lying layers were studied by deep level transient spectroscopy. Results were compared to crystal-TRIM calculations and results from 2 MeV electron irradiations. Previously, ion channeling was disregarded in studies on point defect migration at room temperature using ion implantation in surface layers. In our studies, ion channeling is dominant and it overwhelms any contribution from point defect diffusion.
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| 7. |
- Kortegaard Nielsen, Hanne, et al.
(författare)
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M-center in low-dose proton implanted 4H-SiC; Bistability and change in emission rate
- 2005
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2004. ; , s. 497-500
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Konferensbidrag (refereegranskat)abstract
- 4H-SiC schottky diodes have been implanted with 2.5 MeV protons to a dose of 1 x 10(12) cm(-2) and measured by deep level transient spectroscopy (DLTS). Between annealings at 150 ° C and 200 ° C the whole DLTS-spectra shift in temperature, most clearly revealed for the Z and M-center levels. The shift corresponds to a decrease in emission rate at a given temperature by approximately a factor of 5. It is speculated that the reason for this change in emission rate is to be found in the surrounding material rather than in the defects themselves.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Svensson, B.G., et al.
(författare)
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Ion implantation processing and related effects in SiC
- 2006
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Ingår i: Silicon Carbide and Related Materials 2005, Pts 1 and 2. - 9780878494255 ; , s. 781-786
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Konferensbidrag (refereegranskat)abstract
- A brief survey is given of some recent progress regarding ion implantation processing and related effects in 4H- and 6H-SiC. Four topics are discussed; an empirical ion range distribution simulator, dynamic defect annealing during implantation, formation of highly p(+)-doped layers, and deactivation of N donors by ion-induced defects.
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