| 1. |
- Alfieri, G, et al.
(författare)
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Capacitance spectroscopy study of high energy electron irradiated and annealed 4H-SIC
- 2005
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2004. - ZURICH-UETIKON : TRANS TECH PUBLICATIONS LTD. - 0878499636 ; , s. 365-368
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Konferensbidrag (refereegranskat)abstract
- Deep level transient spectroscopy (DLTS) was employed to investigate the annealing behaviour and thermal stability of radiation induced defects in nitrogen doped 4H-SiC epitaxial layers, grown by chemical vapor deposition (CVD). The epilayers have been irradiated with 15 MeV electrons and an isochronal annealing series has been carried out. The measurements have been performed after each annealing step and six electron traps located in the energy band gap range of 0.42-1.6 eV below the conduction band edge (E-c) have been detected.
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| 2. |
- Domeij, Martin, et al.
(författare)
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Current gain of 4H-SiC bipolar transistors including the effect of interface states
- 2005
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Ingår i: Materials Science Forum. - ZURICH-UETIKON : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 0878499636 ; 483, s. 889-892
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Tidskriftsartikel (refereegranskat)abstract
- The current gain (β) of 4H-SiC BJTs as function of collector current (I-C) has been investigated by DC and pulsed measurements and by device simulations. A measured monotonic increase of β with I-C agrees well with simulations using a constant distribution of interface states at the 4H-SiC/SiO2 interface along the etched side-wall of the base-emitter junction. Simulations using only bulk recombination, on the other hand, are in poor agreement with the measurements. The interface states degrade the simulated current gain by combined effects of localized recombination and trapped charge that influence the surface potential. Additionally, bandgap narrowing has a significant impact by reducing the peak current gain by about 50% in simulations.
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| 3. |
- 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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| 4. |
- Ivanov, A, et al.
(författare)
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High energy resolution detectors based on 4H-SiC
- 2005
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2004. - ZURICH-UETIKON : TRANS TECH PUBLICATIONS LT. - 0878499636 ; , s. 1029-1032
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Konferensbidrag (refereegranskat)abstract
- The spectrometric characteristics of the detectors based on 4H-SiC using 4.8-7.7 MeV a-particles were determined. The Cr Schottky barriers with areas of 1x10(-2) cm(2) were performed by vacuum thermal evaporation on 4H-SiC epitaxial layers grown by chemical vapor deposition (CVD) with thickness 26 and 50 μ m. The concentrations of the uncompensated donors into CVD epitaxial layers were (6-10) x10(14) cm(-3), that allowed to develop a detector depletion region up to 30 μ m using reverse bias of 400 V. The energy resolution less than 20 keV (0.34%) for lines of 5.0-5.5 MeV was achieved that is twice as large of the resolution of high-precision Si-based detectors prepared on specialized technology. The maximum signal amplitude of 4H-SiC - detectors corresponding to the average electron-hole pair generation energy was found to be 7.70 eV.
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| 5. |
- Kalinina, E, et al.
(författare)
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Comparative study of 4H-SiC irradiated with neutrons and heavy ions
- 2005
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2004. - ZURICH-UETIKON : TRANS TECH PUBLICATIONS LTD. - 0878499636 ; , s. 377-380
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Konferensbidrag (refereegranskat)abstract
- The influence of the irradiation with neutrons, Kr+ (245 MeV) and Bi+ (710 MeV) ions on the optical and electrical properties of high-resistivity, high-purity 4H-SiC epitaxial layers grown by chemical vapor deposition was investigated using photoluminescence and deep-level transient spectroscopy. Electrical characteristics were studied using Al and Cr Schottky barriers as well as p(+)-n-n(+) diodes fabricated by Al ion implantation on this epitaxial layers. It was found that both "light" neutrons and high energy heavy ions introduced identical defect centers in 4H-SiC. So, even at extremely high density of the ionization energy of 34 keV/mn, typical for Bi+ ion bombardment, damage structure formation in SiC single crystal is governed by energy loss in elastic collisions.
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| 6. |
- Magnusson, Björn, 1970-, et al.
(författare)
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Optical Characterization of Deep Level Defects in SiC
- 2005
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Ingår i: Materials Science Forum, Vols. 483-485. - 0878499636 ; , s. 341-346
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Konferensbidrag (refereegranskat)abstract
- Deep levels in 4H- and 6H-SiC are characterized by FTIR spectroscopy. Vanadium, chromium and the silicon vacancy related center are listed together with the unidentified defects with emission and absorption in the near IR region. We suggest the UD-1, UD-3 and I-1 to be impurity related while the UD-2 and UD-4 to be intrinsic defects based on annealing behavior and the possibility to create the defect with irradiation. We have also tentatively assigned a new defect center around 1.0 eV to the carbon vacancy-antisite pair instead of the earlier assignment to the UD- 2 defect in 4H-SiC. We have shown that to get more information about the SiC samples a combination of absorption and luminescence techniques are very useful. Further, the use of below bandgap selective excitation is necessary to obtain more information about the defects present in the sample. FTIR absorption and luminescence measurements are useful tools to characterize deep levels important for both semi-insulating material as well as low doped conducting material where the free carrier lifetime is limited by deep levels.
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| 7. |
- Strel'chuk, AM, et al.
(författare)
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Influence of gamma-ray and neutron irradiation on injection characteristics of 4H-SiC pn structures
- 2005
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2004. - 0878499636 ; , s. 993-996
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Konferensbidrag (refereegranskat)abstract
- The effect of gamma-ray and neutron irradiation on recombination current, injection electroluminescense and the value of the lifetime of nonequilibrium carriers for 4H-SiC pn structures was investigated. The irradiation was carried out with gamma-ray (dose 5x10(6) rad) and 1 MeV neutrons in the doses range from 1.2x10(14) cm(-2) to 6.24x10(14) cm(-2). Neutron irradiation with a dose 1.2x10(14) cm(-2) increased the recombination current, decreased the lifetime for deep-level recombination in the space charge region and decreased the intensity of the edge injection electroluminescense (hv(max) ≈ 3.16 eV) by 1.5-2 orders of magnitude; the neutron irradiation with high dose (6.24x10(14) cm(-2)) resulted in increase of the recombination current up to 2 orders of magnitude and decrease of lifetime at least up to 2 orders of magnitude. Gamma-ray irradiation and annealing at temperatures in the range 350-650 K left the recombination current and lifetime practically unchanged.
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