| 1. |
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| 2. |
- Sanjiv, Kumar, et al.
(author)
-
MTH1 Inhibitor TH1579 Induces Oxidative DNA Damage and Mitotic Arrest in Acute Myeloid Leukemia
- 2021
-
In: Cancer Research. - : American Association For Cancer Research (AACR). - 0008-5472 .- 1538-7445. ; 81:22, s. 5733-5744
-
Journal article (peer-reviewed)abstract
- Acute myeloid leukemia (AML) is an aggressive hematologic malignancy, exhibiting high levels of reactive oxygen species (ROS). ROS levels have been suggested to drive leukemogenesis and is thus a potential novel target for treating AML. MTH1 prevents incorporation of oxidized nucleotides into the DNA to maintain genome integrity and is upregulated in many cancers. Here we demonstrate that hematologic cancers are highly sensitive to MTH1 inhibitor TH1579 (karonudib). A functional precision medicine ex vivo screen in primary AML bone marrow samples demonstrated a broad response profile of TH1579, independent of the genomic alteration of AML, resembling the response profile of the standard-of-care treatments cytarabine and doxorubicin. Furthermore, TH1579 killed primary human AML blast cells (CD45+) as well as chemotherapy resistance leukemic stem cells (CD45+Lin−CD34+CD38−), which are often responsible for AML progression. TH1579 killed AML cells by causing mitotic arrest, elevating intracellular ROS levels, and enhancing oxidative DNA damage. TH1579 showed a significant therapeutic window, was well tolerated in animals, and could be combined with standard-of-care treatments to further improve efficacy. TH1579 significantly improved survival in two different AML disease models in vivo. In conclusion, the preclinical data presented here support that TH1579 is a promising novel anticancer agent for AML, providing a rationale to investigate the clinical usefulness of TH1579 in AML in an ongoing clinical phase I trial.
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| 3. |
- von Haartman, Martin, et al.
(author)
-
Random telegraph signal noise in SiGe heterojunction bipolar transistors
- 2002
-
In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:8, s. 4414-4421
-
Journal article (peer-reviewed)abstract
- In this work, random telegraph signal (RTS) noise in SiGe heterojunction bipolar transistors (HBTs) was characterized both as a function of bias voltage and temperature. The RTS amplitudes were found to scale with the total base current, and the characteristic times in the higher and lower RTS state were found to decrease rapidly with bias voltage, approximately as 1/exp(qV(BE)/kT) or stronger. The RTS amplitudes were explained by a model based on voltage barrier height fluctuations across the base-emitter junction induced by trapped carriers in the space charge region. It was shown that the relative RTS amplitudes DeltaI(B)/I-B decrease exponentially with temperature in this model, which also was verified by measurements. The trapping/detrapping mechanism was suggested to be electron and hole capture, where the hole capture process occurs by tunneling. The characteristic times in both the lower and higher RTS state were in some cases found to decrease exponentially with temperature, characteristic for a thermally activated process, and in some cases found to be only weakly temperature dependent. The former behavior was explained by a multiphonon process with thermally activated capture cross sections, and an activation energy of 0.39 eV was extracted. RTS amplitudes proportional to the nonideal base current component or weaker were also found, originating from traps at the Si/SiO2 interface at the emitter periphery. The trapped carriers affect the recombination rate in the base-emitter space charge region, probably by changing the number of carriers. In this case, DeltaI(B)/I-B only showed a weak temperature dependence, which correlates well with this model. Characteristic times that decreased exponentially with temperature were observed, originating from a multiphonon process in the SiO2 with an activation energy for the capture cross section of 0.29 eV.
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| 4. |
- Borné, Yan, et al.
(author)
-
Cadmium, Carotid Atherosclerosis, and Incidence of Ischemic Stroke.
- 2017
-
In: Journal of the American Heart Association. - 2047-9980. ; 6:12
-
Journal article (peer-reviewed)abstract
- Exposure to cadmium has been associated with carotid plaques, inflammation in carotid plaques, and increased risk of ischemic stroke. This study examined the separate and interacting effects of blood cadmium levels and carotid plaques on the risk of incident ischemic stroke.Cadmium levels were measured in 4156 subjects (39.2% men; mean±SD age 57.3±5.9years) without history of stroke, from the Malmö Diet and Cancer cohort. The right carotid artery was examined using B-mode ultrasound examination at baseline. Incidence of ischemic stroke was monitored over a mean follow-up of 16.7years. Carotid plaque was present in 34.5% of participants. Cadmium was significantly higher in subjects with plaque (mean±SD: 0.53±0.58μg/L versus 0.42±0.49μg/L; P<0.001). A total of 221 subjects had ischemic stroke during the follow-up. Incidence of ischemic stroke was associated both with carotid plaque (hazard ratio 1.44, 95% confidence interval, 1.09-1.90, P=0.009) and cadmium (hazard ratio for quartile [Q] 4 versus Q1-3: 1.95, confidence interval, 1.33-2.85, P=0.001), after adjustment for risk factors. There was a significant interaction between cadmium and plaque with respect to risk of ischemic stroke (P=0.011). Adjusted for risk factors, subjects with plaque and cadmium in Q4 had a hazard ratio of 2.88 (confidence interval, 1.79-4.63) for ischemic stroke, compared with those without plaque and cadmium in Q1 to Q3.Cadmium was associated with incidence of ischemic stroke, both independently and in synergistic interaction with carotid plaques. This supports the hypothesis that cadmium promotes vulnerability of carotid plaques, thereby increasing the risk of rupture and ischemic stroke.
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| 5. |
- Buono, Benedetto, et al.
(author)
-
Current Gain Degradation in 4H-SiC Power BJTs
- 2011
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 679-680, s. 702-705
-
Journal article (peer-reviewed)abstract
- SiC airs are very attractive for high power application, but long term stability is still problematic and it could prohibit commercial production of these devices. The aim of this paper is to investigate the current gain degradation in BJTs with no significant degradation of the on-resistance. Electrical measurements and simulations have been used to characterize the behavior of the BJT during the stress test. Current gain degradation occurs, the gain drops from 58 before stress to 43 after 40 hours, and, moreover, the knee current shows fluctuations in its value during the first 20 hours. Current gain degradation has been attributed to increased interface traps or reduced lifetime in the base-emitter region or small stacking faults in the base-emitter region, while fluctuations of the knee current might be due to stacking faults in the collector region.
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| 6. |
- Buono, Benedetto, et al.
(author)
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Influence of Emitter Width and Emitter-Base Distance on the Current Gain in 4H-SiC Power BJTs
- 2010
-
In: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 57:10, s. 2664-2670
-
Journal article (peer-reviewed)abstract
- The influence of the emitter-base geometry on the current gain has been investigated by means of measurements and simulations. Particular attention has been placed on the emitter width and on the distance between the emitter edge and the base contact. When the emitter width is decreased from 40 to 8 mu m, the current gain is reduced by 20%, whereas when the distance between the base contact and the emitter edge is decreased from 5 to 2 mu m, the current gain is reduced by 10%. Simulations have been used to investigate the reasons for the current gain reduction. The reduction of the emitter width induces two mechanisms of current gain reduction: earlier forward biasing of the base-collector junction and higher recombination in the emitter region. Both mechanisms result from the higher current density flowing under the emitter region. Placing the base contact very close to the emitter edge increases the base current by increasing the gradient of the electron concentration toward the base contact. The effect of increasing the base doping in the extrinsic region has been simulated, and the results demonstrate that the current gain can be improved if a high doping concentration in the range of 5 x 10(18) cm(-3) is used.
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| 7. |
- Buono, Benedetto, et al.
(author)
-
Investigation of Current Gain Degradation in 4H-SiC Power BJTs
- 2012
-
In: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 717-720, s. 1131-1134
-
Journal article (peer-reviewed)abstract
- The current gain degradation of 4H-SiC BJTs with no significant drift of the on-resistance is investigated. Electrical stress on devices with different emitter widths suggests that the device design can influence the degradation behavior. Analysis of the base current extrapolated from the Gummel plot indicates that the reduction of the carrier lifetime in the base region could be the cause for the degradation of the gain. However, analysis of the base current of the base-emitter diode shows that the degradation of the passivation layer could also influence the reduction of the current gain.
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| 8. |
- Buono, Benedetto, et al.
(author)
-
Modeling and Characterization of Current Gain Versus Temperature in 4H-SiC Power BJTs
- 2010
-
In: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9383 .- 1557-9646. ; 57:3, s. 704-711
-
Journal article (peer-reviewed)abstract
- Accurate physical modeling has been developed to describe the current gain of silicon carbide (SiC) power bipolar junction transistors (BJTs), and the results have been compared with measurements. Interface traps between SiC and SiO2 have been used to model the surface recombination by changing the trap profile, capture cross section, and concentration. The best agreement with measurement is obtained using one single energy level at 1 eV above the valence band, a capture cross section of 1 x 10(-15) cm(2), and a trap concentration of 2 x 10(12) cm(-2). Simulations have been performed at different temperatures to validate the model and characterize the temperature behavior of SiC BJTs. An analysis of the carrier concentration at different collector currents has been performed in order to describe the mechanisms of the current gain fall-off at a high collector current both at room temperature and high temperatures. At room temperature, high injection in the base ( which has a doping concentration of 3 x 10(17) cm(-3)) and forward biasing of the base-collector junction occur simultaneously, causing an abrupt drop of the current gain. At higher temperatures, high injection in the base is alleviated by the higher ionization degree of the aluminum dopants, and then forward biasing of the base-collector junction is the acting mechanism for the current gain fall-off. Forward biasing of the base-collector junction can also explain the reduction of the knee current with increasing temperature by means of the negative temperature dependence of the mobility.
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| 9. |
- Buono, Benedetto, et al.
(author)
-
Modeling and Characterization of the ON-Resistance in 4H-SiC Power BJTs
- 2011
-
In: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 58:7, s. 2081-2087
-
Journal article (peer-reviewed)abstract
- The ON-resistance of silicon carbide bipolar transistors is characterized and simulated. Output characteristics are compared at different base currents and different temperatures in order to validate the physical model parameters. A good agreement is obtained, and the key factors, which limit the improvement of R-ON, are identified. Surface recombination and material quality play an important role in improving device performances, but the device design is also crucial. Based on simulation results, a design that can enhance the conductivity modulation in the lowly doped drift region is proposed. By increasing the base doping in the extrinsic region, it is possible to meet the requirements of having low voltage drop, high current density, and satisfactory forced current gain. According to simulation results, if the doping is 5 x 10(18) cm(-3), it is possible to conduct 200 A/cm(2) at V-CE = 1 V by having a forced current gain of about 8, which represents a large improvement, compared with the simulated value of only one in the standard design.
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| 10. |
- Buono, Benedetto
(author)
-
Simulation and Characterization of Silicon Carbide Power Bipolar Junction Transistors
- 2012
-
Doctoral thesis (other academic/artistic)abstract
- The superior characteristics of silicon carbide, compared with silicon, have suggested considering this material for the next generation of power semiconductor devices. Among the different power switches, the bipolar junction transistor (BJT) can provide a very low forward voltage drop, a high current capability and a fast switching speed. However, in order to compete on the market, it is crucial to a have high current gain and a breakdown voltage close to ideal. Moreover, the absence of conductivity modulation and long-term stability has to be solved. In this thesis, these topics are investigated comparing simulations and measurements. Initially, an efficient etched JTE has been simulated and fabricated. In agreement with the simulations, the fabricated diodes exhibit the highest BV of around 4.3 kV when a two-zone JTE is implemented. Furthermore, the simulations and measurements demonstrate a good agreement between the electric field distribution inside the device and the optical luminescence measured at breakdown. Additionally, an accurate model to simulate the forward characteristics of 4H-SiC BJTs is presented. In order to validate the model, the simulated current gains are compared with measurements at different temperatures and different base-emitter geometries. Moreover, the simulations and measurements of the on-resistance are compared at different base currents and different temperatures. This comparison, coupled with a detailed analysis of the carrier concentration inside the BJT, indicates that internal forward biasing of the base-collector junction limits the BJT to operate at high current density and low forward voltage drop simultaneously. In agreement with the measurements, a design with a highly-doped extrinsic base is proposed to alleviate this problem. In addition to the static characteristics, the comparison of measured and simulated switching waveforms demonstrates that the SiC BJT can provide fast switching speed when it acts as a unipolar device. This is crucial to have low power losses during transient. Finally, the long-term stability is investigated. It is observed that the electrical stress of the base-emitter diode produces current gain degradation; however, the degradation mechanisms are still unclear. In fact, the analysis of the measured Gummel plot suggests that the reduction of the carrier lifetime in the base-emitter region might be only one of the causes of this degradation. In addition, the current gain degradation due to ionizing radiation is investigated comparing the simulations and measurements. The simulations suggest that the creation of positive charge in the passivation layer can increase the base current; this increase is also observed in the electrical measurements.
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| 11. |
- Buono, Benedetto, et al.
(author)
-
Simulations of Open Emitter Breakdown Voltage in SiC BJTs with non Implanted JTE
- 2009
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 615-617, s. 841-844
-
Journal article (peer-reviewed)abstract
- Ion implantation for selective doping of SiC is problematic due to damage generation during the process and low activation of dopants. In SiC bipolar junction transistor (BJT) the junction termination extension (JTE) can be formed without ion implantation using instead a controlled etching into the epitaxial base. This etched JTE is advantageous because it eliminates ion implantation induced damage and the need for high temperature annealing. However, the dose, which is controlled by the etched base thickness and doping concentration, plays a crucial role. In order to find the optimum parameters, device simulations of different etched base thicknesses have been performed using the software Sentaurus Device. A surface passivation layer consisting of silicon dioxide, considering interface traps and fixed trapped charge, has been included in the analysis by simulations. Moreover a comparison with measured data for fabricated SiC BJTs has been performed.
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| 12. |
- Buono, Benedetto, et al.
(author)
-
Temperature Modeling and Characterization of the Current Gain in 4H-SiC Power BJTs
- 2010
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 645-648, s. 1061-1064
-
Journal article (peer-reviewed)abstract
- The current gain of 4H-SiC BJTs has been modeled using interface traps between SIC and SiO2 to describe surface recombination, by a positive temperature dependence of the carrier lifetime in the base region and by bandgap narrowing in the emitter region. The interface traps have been modeled by one single level at 1 eV above the valence band, with capture cross section of 1 x 10(-15) cm(2) and concentration of 2 x 10(12) cm(-2). The temperature behavior of SiC BJTs has been simulated and the results have been compared with measurements. An analysis of the carrier concentration has been performed in order to describe the mechanisms for fall-off of the current gain at high collector current. At room temperature high injection in the base and forward biasing of the base-collector junction occur simultaneously causing an abrupt drop of the current gain. At higher temperatures high injection in the base is alleviated by the higher ionization degree of the aluminum dopants, and then forward biasing of the base-collector junction is the only acting mechanism for the current gain fall-off at high collector current. This mechanism and the negative temperature dependence of the carrier mobility can also explain the reduction of the knee current for gain fall-off with increasing temperature. Simulations with different emitter widths have been also performed and analyzed to characterize the emitter size effect. Higher current density caused by reducing the emitter width introduces higher carrier recombination in the emitter region, leading to a reduction of the current gain.
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| 13. |
- Danielson, E., et al.
(author)
-
Investigation of thermal properties in fabricated 4H-SiC high power bipolar transistors
- 2003
-
In: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 47:4, s. 639-644
-
Journal article (peer-reviewed)abstract
- Silicon carbide bipolar junction transistors have been fabricated and investigated. The transistors had a maximum current gain of approximately 10 times, and a breakdown voltage of 450 V. When operated at high power densities the device showed a clear self-heating effect, decreasing the current gain. The junction temperature was extracted during self-heating to approximately 150 degreesC, using the assumption that the current gain only depends on temperature. Thermal images of a device under operation were also recorded using an infrared camera, showing a significant temperature increase in the vicinity of the device. The device was also tested in a switched setup, showing fast turn on and turn off at 1 MHz and 300 V supply voltage. Device simulations have been used to analyze the measured data. The thermal conductivity is fitted against the self-heating, and the lifetime in the base is fitted against the measurement of the current gain.
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| 14. |
- Danielsson, Erik, et al.
(author)
-
A 4H-SiC BJT with an epitaxially regrown extrinsic base layer
- 2005
-
In: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 483, s. 905-908
-
Journal article (peer-reviewed)abstract
- 4H-SiC BJTs were fabricated using epitaxial regrowth instead of ion implantation to form a highly doped extrinsic base layer necessary for a good base ohmic contact. A remaining p(+) regrowth spacer at the edge of the base-emitter junction is proposed to explain a low current gain of 6 for the BJTs. A breakdown voltage of 1000 V was obtained for devices with Al implanted JTE.
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| 15. |
- Danielsson, Erik, et al.
(author)
-
Extrinsic base design of SiC bipolar transistors
- 2004
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 457-460:II, s. 1117-1120
-
Journal article (peer-reviewed)abstract
- The SiC npn bipolar junction transistor (BJT) is a very promising device for high voltage and high power switches. The SiC BJT has, due to junction voltage cancellation, potentially a low on-resistance. However, the high resistivity in the base layer can induce a locally forward biased base collector junction and a premature current from the base to collector at on-state. In this work we propose a new technique to fabricate the extrinsic base using regrowth of the extrinsic base layer. This technique can put the highly doped region of the extrinsic base a few tenths of a micron from the intrinsic region. We also propose a new mobility model in our simulations to correctly account for the ionized impurities in minority carrier transport and elevated temperature.
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| 16. |
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| 17. |
- Domeij, Martin, et al.
(author)
-
2.2 kV SiC BJTs with low V(CESAT) fast switching and short-circuit capability
- 2010
-
In: SILICON CARBIDE AND RELATED MATERIALS 2009, PTS 1 AND 2. ; , s. 1033-1036
-
Conference paper (peer-reviewed)abstract
- This paper reports large active area (15 mm(2)) 4H-SiC BJTS with a low V(CESAT)=0.6 V at 1(C)=20 A (J(C)=133 A/cm(2)) and an open-base breakdown voltage BV(CEO)=2.3 kV at T=25 degrees C. The corresponding room temperature specific on-resistance R(SP.ON)=4.5 m Omega cm(2) is to the authors knowledge the lowest reported value for a large area SiC BJT blocking more than 2 kV. The onstate and blocking characteristics were analyzed by device simulation and found to be in good agreement with measurements. Fast switching with VcE rise- and fall-times in the range of 20-30 ns was demonstrated for a 6 A 1200 V rated SiC BJT. It was concluded that high dynamic base currents are essential for fast switching to charge the BJT parasitic base-collector capacitance. In addition, 10 mu s short-circuit capability with V(CE)=800 V was shown for the 1200 V BJT.
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| 18. |
- Domeij, Martin, et al.
(author)
-
Analysis of the base current and saturation voltage in 4H-SiC power BJTs
- 2007
-
In: 2007 European Conference On Power Electronics And Applications. - 9789075815115 ; , s. 2744-2750
-
Conference paper (peer-reviewed)abstract
- Silicon carbide (SiC) power bipolar junction transistors are interesting competitors to Si IGBTs for 1200 V power electronics applications. Advantages of SiC BJTs are low collector-emitter saturation voltages, little stored charge and high temperature capability. In this work, SiC NPN power BJTs with common emitter current gains of 40 have been fabricated and characterized. Electrical measurements for BJTs with different emitter widths indicate that the current gain is limited by surface recombination. A low value of V-CESAT=0.9 V at J(C)=100 A/cm(2) was obtained for small and large area (3.4 mm(2)) BJTs and correlated with the formation of low-resistive ohmic contacts to the base. Large area BJTs were shown to operate with a current gain of 48 in pulsed mode at a collector current of 12 A corresponding to J(C)=360 A/cm(2).
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| 19. |
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| 20. |
- Domeij, Martin, et al.
(author)
-
Current gain dependence on emitter width in 4H-SiC BJTs
- 2006
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9780878494255 ; 527-529, s. 1425-1428
-
Journal article (peer-reviewed)abstract
- This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain beta = 64 and a breakdown voltage of 1100 V. The high beta value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The current gain of the BJTs increases with increasing emitter width indicating a significant influence of surface recombination. This "emitter-size" effect is in good agreement with device simulations including recombination in interface states at the etched termination of the base-emitter junction.
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| 21. |
- Domeij, Martin, et al.
(author)
-
Current gain of 4H-SiC bipolar transistors including the effect of interface states
- 2005
-
In: Materials Science Forum. - ZURICH-UETIKON : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 0878499636 ; 483, s. 889-892
-
Journal article (peer-reviewed)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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| 22. |
- Domeij, Martin, et al.
(author)
-
Dynamic avalanche in 3.3-kV Si power diodes
- 1999
-
In: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9383 .- 1557-9646. ; 46:4, s. 781-786
-
Journal article (peer-reviewed)abstract
- Measurements of the safe reverse recovery limit were performed for 3.3-kV Si power diodes using a novel optical experimental technique. In this experiment, influence of the junction termination is effectively eliminated by optical generation of a laterally-localized carrier plasma. The turn-off failures observed in measurements at two temperatures showed no temperature dependence and could not be reproduced in ordinary one-dimensional (1-D) or two-dimensional (2-D) device simulations. To simulate the stability of the current density toward current filamentation, two 1-D diodes with an area ratio 1:19 and a 10% difference in initial carrier plasma level, were simulated in parallel. This resulted in a strongly inhomogeneous current distribution, and a rapid reverse voltage fall resembling the measured turn-off failures. Inhomogeneous current distribution in these simulations appears as the current decay ceases due to impact ionization, in qualitative agreement with a current instability condition proposed by Wachutka [1].
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| 23. |
- Domeij, Martin, et al.
(author)
-
Dynamic avalanche in Si power diodes and impact ionization at the nn(+) junction
- 2000
-
In: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 44:3, s. 477-485
-
Journal article (peer-reviewed)abstract
- The reverse recovery failure limit was measured with an optical technique for power diodes which sustain high levels of dynamic avalanche. Measurements and simulations indicate that these diodes withstand dynamic avalanche at the pn-junction and eventually fail as a result of a strongly inhomogeneous current distribution caused by the onset of impact ionisation at the diode nn(+) junction - a mechanism similar to the reverse bias second breakdown of bipolar transistors.
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| 24. |
- Domeij, Martin, et al.
(author)
-
Geometrical effects in high current gain 1100-V 4H-SiC BJTs
- 2005
-
In: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 26:10, s. 743-745
-
Journal article (peer-reviewed)abstract
- This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain beta = 64 and a breakdown voltage of 1100 V. The high beta value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The BJTs show a clear emitter-size effect indicating that surface recombination has a significant influence on beta. A minimum distance of 2-3 mu m between the emitter edge and base contact implant was found adequate to avoid a substantial beta reduction.
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| 25. |
- Domeij, Martin, et al.
(author)
-
High current gain silicon carbide bipolar power transistors
- 2006
-
In: Proceedings of the 18th International Symposium on Power Semiconductor Devices and ICs. ; , s. 141-144
-
Conference paper (peer-reviewed)abstract
- Silicon carbide NPN bipolar junction transistors were fabricated and a current gain exceeding 60 was obtained for a BJT with a breakdown voltage BV(CEO)=1100 V. A reduction of the current gain was observed after contact annealing at 950 degrees C and this was attributed to degradation of the oxide passivation. Device simulations with varying emitter doping resulted in a maximum current gain for an emitter doping around 1(.)10(19) cm(-3). Resistive turn-off measurements were performed and a minimum collector-emitter voltage (V(CE)) rise-time of 40 ns was found. The VCE rise-time showed a clear dependence on the on-state base current thus indicating a significant stored charge.
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| 26. |
- Domeij, Martin, et al.
(author)
-
Measurements and simulations of self-heating and switching with 4H-SIC power BJTs
- 2003
-
In: IEEE International Symposium on Power Semiconductor Devices and ICs (ISPSD). - Cambridge. ; , s. 375-378
-
Conference paper (peer-reviewed)abstract
- Transient measurements and device simulations were performed to investigate self-heating and switching with 4H-SiC BJTs. A current gain decrease was found during self-heating presumably due to reduced electron mobility with increasing temperature. Surface recombination increased the simulated maximum temperature but the current gain decrease during self-heating was similar as for bulk recombination. A fast switching of 0.5 A and 200 V was shown with a voltage rise-time of about 70 ns and fall-time of 50 ns. Turn-off measurements show a noticeable delay time before fall-off of the emitter current, indicating a significant amount of stored carriers in the base.
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| 27. |
|
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| 28. |
- Domeij, Martin, et al.
(author)
-
SiC power bipolar junction transistors : Modeling and improvement of the current gain
- 2005
-
In: 2005 European Conference on Power Electronics and Applications. - Dresden : IEEE. - 9075815085 - 9789075815085 ; , s. 1665888-
-
Conference paper (peer-reviewed)abstract
- Epitaxial silicon carbide bipolar junction transistors (BJTs) for power switching applications have been designed and fabricated with a maximum breakdown voltage of 1100 V. The BJTs have high common emitter current gains with maximum values exceeding 60, a result that is attributed to design optimization of the base and emitter layers and to a high material quality obtained by a continuous epitaxial growth. Device simulations of the current gain as function of collector current have been compared with measurements. The measurements show a clear emitter-size effect that is in good agreement with simulations including surface recombination in interface states at the etched termination of the base-emitter junction. Simulations indicate an optimum emitter doping around 1-1019 cm-3 in agreement with typical state-of-the-art BJTs.
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| 29. |
- Domeij, Martin, et al.
(author)
-
Stable dynamic avalanche in Si power diodes
- 1999
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 74:21, s. 3170-3172
-
Journal article (peer-reviewed)abstract
- A stable dynamic avalanche at a maximum power density of about 2.4 MW/cm(2) was measured in small areas of 3.3 kV Si power diodes, using an optical measurement technique, and very good dynamic ruggedness was verified in a conventional turn-off measurement. Device simulations of a diode with a shallow n(+) emitter indicate that impact ionization at the nn(+) junction can result in negative differential resistance (NDR) and current filamentation, whereas a deep n(+) emitter in the experimentally studied diode suppresses NDR. It is, therefore, proposed that the deep n(+) emitter is important for the stable dynamic avalanche.
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| 30. |
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| 31. |
- Eriksson, K. G. Peter, et al.
(author)
-
A Simple and Reliable Electrical Method for Measuring the Junction Temperature and Thermal Resistance of 4H-SiC Power Bipolar Junction Transistors
- 2009
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 600-603, s. 1171-1174
-
Journal article (peer-reviewed)abstract
- To determine the maximum allowed power dissipation in a power transistor, it is important to determine the relationship between junction temperature and power dissipation. This work presents a new method for measuring the junction temperature in a SiC bipolar junction transistor (BJT) that is self-heated during DC forward conduction. The method also enables extraction of the thermal resistance between junction and ambient by measurements of the junction temperature as function of DC power dissipation. The basic principle of the method is to determine the temperature dependent IN characteristics of the transistor under pulsed conditions with negligible self-heating, and compare these results with DC measurements with self-heating. Consistent results were obtained from two independent temperature measurements using the temperature dependence of the current gain, and the temperature dependence of the base-emitter IN characteristics, respectively.
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| 32. |
- Farese, Luca, et al.
(author)
-
Experimental Study of Degradation in 4H-SiC BJTs by Means of Electrical Characterization and Electroluminescence
- 2010
-
In: SILICON CARBIDE AND RELATED MATERIALS 2009. ; , s. 1037-1040
-
Conference paper (peer-reviewed)abstract
- SiC power bipolar junction transistors (BJTs), for high voltage applications, have been studied under elevated temperature and electrical stress conditions. Electroluminescence has been used to capture effects of defect motion and growth, in complete transistor structures, leading to a quantifiable degradation in the electrical performance. The observed degradation of current gain (beta) and on-resistance (RON) was relatively modest and saturated after a limited stress time, resulting in stable device performance. The characteristic wavelength (450 nm) of the electroluminescence, or light emission, in the visual and near infrared (NIR) range, coupled to the shape of the defects indicates that basal plane dislocations and stacking faults are involved.
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| 33. |
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| 34. |
- Gepner, B. D., et al.
(author)
-
Comparison of human body models in frontal crashes with reclined seatback
- 2019
-
In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 293-307
-
Conference paper (peer-reviewed)abstract
- Reclined seating configurations, relevant to the future of Autonomous Driving Systems is likely to challenge the current state-of-the-art restraint systems. Human body models (HBM) offer an attractive tool to support the design process, however their validity in the reclined scenario remains questionable. The goal of this study is to compare the response of selected HBMs in the frontal, reclined scenario, while utilizing a new prototype restraint system. A sled model with a generic seat, 50 deg seatback recline angle and a prototype 3-point belt system was used in this study. Four different male HBMs were compared, the Global Human Body Model Consortium (GHBMC) simplified occupant model (GHBMC-S), the GHBMC detailed model (GHBMC-D), Total Human Model for Safety SAFER (THUMS-S) model, and THUMS-v5 model. All HBMs showed good pelvis engagement, except GHBMC-D that submarined under the lap belt. Additionally, large differences were observed in pelvis and lumbar spine response between GHBMC and THUMS family models. Since no relevant PMHS data is currently available, it is impossible to evaluate the biofidelity of these models in the reclined scenarios. Evaluating the relative biofidelity of these models can only be accomplished with experimental data capturing detailed 3D skeletal kinematics and all the boundary forces necessary for model evaluation.
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| 35. |
- Gepner, B. D., et al.
(author)
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Evaluation of GHBMC, THUMS and SAFER Human Body Models in Frontal Impacts in Reclined Postures
- 2022
-
In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2022-September, s. 116-143
-
Conference paper (peer-reviewed)abstract
- Virtual tools, such as human body models (HBMs), can support advances in vehicle development and restraint system design. The goal of this study is to evaluate selected HBMs against data from recent reclined post-mortem human subject (PMHS) tests. Three HBMs - the Global Human Body Modelling Consortium detailed model v.6.0, Total Human Model for Safety v.6.0, and SAFER HBM v.10 - were used in this study. The models were positioned with respect to the average PMHS position and utlised a previously developed environment model. The HBMs were evaluated comparing belt engagement, boundary forces and displacements (in the seat and belt), and the trajectories of the head, T1, T8, T11, L1, L3, and pelvis. The HBMs' belt engagement, boundary forces and displacements, and X-direction (fore-aft) trajectories were all generally consistent with the PMHS. All HBMs predicted more downward motion of the head and T1 compared to the PMHS. The HBMs also showed rearward pelvis pitch at peak lap belt force, opposite to the PMHS. Some of these differences were associated with differences in flexion of the lumbar spine. This is the first study to provide an in-depth evaluation of multiple reclined HBMs in frontal crashes compared to reclined PMHS.
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| 36. |
- Ghandi, Reza, et al.
(author)
-
Backside Nickel Based Ohmic Contacts to n-type Silicon Carbide
- 2009
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 600-603, s. 635-638
-
Journal article (peer-reviewed)abstract
- This work focuses on Ni ohmic contacts to the C-face (backside) of n-type 4H-SiC substrates. Low-resistive ohmic contacts to the wafer backside are important especially for vertical power devices. Ni contacts were deposited using E-beam evaporation and annealed at different temperatures (700-1050 degrees C) in RTP to obtain optimum conditions for forming low resistive ohmic contacts. Our results indicate that 1 min annealing at temperatures between 950 and 1000 degrees C provides high quality ohmic contacts with a contact resistivity of 2.3x10(-5) Omega cm(2). Also our XRD results show that different Ni silicide phases appear in this annealing temperature range.
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| 37. |
- Ghandi, Reza, et al.
(author)
-
Experimental evaluation of different passivation layers on the performance of 3kV 4H-SiC BJTs
- 2010
-
In: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 645-648:Part 1-2, s. 661-664
-
Journal article (peer-reviewed)abstract
- In this work, the electrical performance in terms of maximum current gain, ON-resistance and blocking capability has been compared for 4H-SiC BJTs passivated with different surface passivation layers. Variation in BJT performance has been correlated to densities of interface traps and fixed oxide charge, as evaluated through MOS capacitors. Six different methods were used to fabricate SiO2 surface passivation on BJT samples from the same wafer. The highest current gain was obtained for PECVD deposited SiO2 which was annealed in N2O ambient at 1100 degrees C during 3 hours. Variations in breakdown voltage for different surface passivations were also found, and this is attributed to differences in fixed oxide charge that can affect the optimum dose of the high voltage JTE termination.
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| 38. |
- Ghandi, Reza, et al.
(author)
-
Fabrication of 2700-v 12-m Omega center dot cm(2) non ion-implanted 4H-SiC BJTs with common-emitter current gain of 50
- 2008
-
In: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 29:10, s. 1135-1137
-
Journal article (peer-reviewed)abstract
- High-voltage blocking (2.7-kV) implantation-free SiC bipolar junction transistors with low ON-state resistance (12 m Omega . cm(2)) and high common-emitter current gain of 50 have been fabricated. A graded-base doping was implemented to provide a low-resistive ohmic contact to the epitaxial base. This design features a fully depleted base layer close to the breakdown voltage providing an efficient epitaxial JTE without ion implantation. Eliminating all ion implantation steps in this approach is beneficial for avoiding high-temperature dopant activation annealing and for avoiding generation of lifetime-killing defects that reduce the current gain.
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| 39. |
- Ghandi, Reza, et al.
(author)
-
High current-gain implantation-free 4H-SiC Monolithic Darlington Transistor
- 2011
-
In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:2, s. 188-190
-
Journal article (peer-reviewed)abstract
- An implantation-free 4H-SiC Darlington transistor with high current gain of 2900 ( JC= \970A/cm2) and VCE) = 6V) at room temperature is reported. The device demonstrates a record maximum current gain of 640 at 200 hC, offering an attractive solution for high-temperature applications. The monolithic Darlington device exhibits an open-base breakdown voltage of 1 kV that is less than the optimum bulk breakdown due to isolation trench between the driver and the output bipolar junction transistor. On the same wafer, a monolithic Darlington pair with a nonisolated base layer was also fabricated. At room temperature, this device shows a maximum current gain of 1000 and an open-base breakdown voltage of 2.8 kV, which is 75% of the parallel-plane breakdown voltage
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| 40. |
- Ghandi, Reza, et al.
(author)
-
High Voltage (2.8 kV) Implantation-free 4H-SiC BJTs with Long-TermStability of the Current Gain
- 2011
-
In: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 58:8, s. 2665-2669
-
Journal article (peer-reviewed)abstract
- In this work, implantation-free 4H-SiC BJTs with high breakdown of 2800 V have been fabricated utilizing acontrolled two-step etched junction termination extension (JTE). The small area devices show a maximum dc current gainof 55 at Ic=0.33 A (JC=825 A/cm2) and VCESAT = 1.05 V at Ic = 0.107 A that corresponds to a low ON-resistance of 4mΩ·cm2. The large area device have a maximum dc current gain of 52 at Ic = 9.36 A (JC=289 A/cm2) and VCESAT = 1.14 Vat Ic = 5 A that corresponds to an ON-resistance of 6.8 mΩ·cm2. Also these devices demonstrate a negative temperaturecoefficient of the current gain (β=26 at 200°C) and a positive temperature coefficient of the ON-resistance (RON = 10.2mΩ·cm2 at 200°C). The small area BJT shows no bipolar degradation and low current gain degradation after 150 Hrs stressof the base-emitter diode with current level of 0.2A (JE=500 A/cm2). Also, large area BJT shows a VCE fall time of 18 nsduring turn-on and a VCE rise time of 10 ns during turn-off for 400 V switching characteristics.
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| 41. |
- Ghandi, Reza, et al.
(author)
-
High-Voltage 4H-SiC PiN Diodes With Etched Junction Termination Extension
- 2009
-
In: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 30:11, s. 1170-1172
-
Journal article (peer-reviewed)abstract
- Implantation-free mesa-etched 4H-SiC PiN diodes with a near-ideal breakdown voltage of 4.3 kV (about 80% of the theoretical value) were fabricated, measured, and analyzed by device simulation and optical imaging measurements at breakdown. The key step in achieving a high breakdown voltage is a controlled etching into the epitaxially grown p-doped anode layer to reach an optimum dopant dose of similar to 1.2 x 10(13) cm(-2) in the junction termination extension (JTE). Electroluminescence revealed a localized avalanche breakdown that is in good agreement with device simulation. A comparison of diodes with single-and double-zone etched JTEs shows a higher breakdown voltage and a less sensitivity to varying processing conditions for diodes with a two-zone JTE.
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| 42. |
- Ghandi, Reza, et al.
(author)
-
High Voltage, Low On-resistance 4H-SiC BJTs with Improved Junction Termination Extension
- 2011
-
In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 679-680, s. 706-709
-
Journal article (peer-reviewed)abstract
- In this work, implantation-free 4H-SiC bipolar transistors with two-zone etched-JTE and improved surface passivation are fabricated. This design provides a stable open-base breakdown voltage of 2.8 kV which is about 75% of the parallel plane breakdown voltage. The small area devices shows a maximum dc current gain of 55 at Ic=0.33 A (J(C)=825 A/cm(2)) and V-CESAT = 1.05 V at Ic = 0.107 A that corresponds to a low ON-resistance of 4 m Omega.cm(2). The large area device shows a maximum dc current gain of 52 at Ic = 9.36 A (J(C)=312 A/cm(2)) and V-CESAT = 1.14 V at Ic = 5 A that corresponds to an ON-resistance of 6.8 m Omega.cm(2). Also these devices demonstrate a negative temperature coefficient of the current gain (beta=26 at 200 degrees C) and positive temperature coefficient of the ON-resistance (R-ON = 10.2 m Omega.cm(2)).
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| 43. |
- Ghandi, Reza, et al.
(author)
-
Implantation-Free Low on-resistance 4H-SiC BJTs with Common-Emitter Current Gain of 50 and High Blocking Capability
- 2009
-
In: Materials Science Forum. - STAFA-ZURICH : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9780878493340 ; 615-617, s. 833-836
-
Journal article (peer-reviewed)abstract
- In this study, high voltage blocking (2.7 kV) implantation-free SiC Bipolar Junction Transistors with low on-state resistance (12 m Omega-cm(2)) and high common-emitter current gain of 50 have been fabricated. A graded base doping was implemented to provide a low resistive ohmic contact to the epitaxial base. This design features a fully depleted base layer close to the breakdown voltage providing an efficient epitaxial JTE without ion implantation. Eliminating all ion implantation steps in this approach is beneficial for avoiding high temperature dopant activation annealing and for avoiding generation of life-time killing defects that reduces the current gain. Also in this process large area transistors showed common-emitter current gain of 38 and open-base breakdown voltage of 2 kV.
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| 44. |
- Ghandi, Reza, et al.
(author)
-
Influence of crystal orientation on the current gain in 4H-SiC BJTs
- 2010
-
In: Device Research Conference - Conference Digest, DRC. - 9781424478705 ; , s. 131-132
-
Conference paper (peer-reviewed)abstract
- The 4H-SiC bipolar junction transistors (BJT) are considered as efficient high power switching devices due to the ability of obtaining very low specific on-resistance compared to FET based devices. However, one drawback with the present high voltage BJTs is the relatively low current gain. To reduce the power required by the drive circuit, it is important to increase the common-emitter current gain ( #x03B2;). 4H-SiC (0001) Si-face has become a favorable plane for vertical power BJTs with epitaxial layers that shows higher mobility along the c-axis and provides higher current gain. Furthermore, important progress on improving the current gain focused on the quality of surface passivation at the SiC/SiO2 interface has been reported during previous years. Higher quality of passivation can provide less interface traps and thereby minimizes the surface recombination current. Conventionally, vertical 4H-SiC BJTs are fabricated along the [11_00] direction on (0001) Si-face. However due to anisotropic properties of 4H-SiC, different orientations on Si-face can also affect the base current of the BJT through variation of mobility and interface traps density distribution along each direction. In this work, single-finger small area BJTs are fabricated on (0001) Si-face along [12_10], [011_0], [112_0] and [11_00] directions. This design can provide various orientations of BJTs that corresponds to an angular range between 0 to 180 degrees relative to conventional [11_00] direction. The goal was to find a correlation between different crystallographic orientation, mobility and interface traps density distribution through transistor characteristics and finally comparison with simulation. Fig.1 shows a cross section and top view of fabricated BJTs. The n+ emitter epi-layer is 1.35 #x03BC;m nitrogen doped to 6 #x00D7;1018 cm-3 and capped by 200-nm-thick 2 #x00D7;1019 cm-3 layer. The base epi-layer is 650 nm Al-d- - oped with concentration of 4.3 #x00D7;1017 cm-3. The drift n- epilayer is 20 #x03BC;m thick and doped to 6 #x00D7;1015 cm-3. Inductively coupled plasma (ICP) etching with an oxide mask was used to form emitter and base mesas. Fig.2 is a comparison of the maximum current gain with different orientations normalized to the maximum current gain along [11_00] before surface passivation and contact metallization. The results indicate that the maximum current gain is orientation-dependent and has a maximum for BJTs with the emitter edge aligned to the [112_0] direction. The variation effect of planar mobility and interface traps concentration on the current gain is simulated based on the previous work and is illustrated in Fig.3. The simulation shows that interface oxide charges has more influence on the current gain compared to the mobility and higher current gain is attributed to lower oxide interface charges. The orientation dependence of the transistor parameters such as maximum current gain after passivation and the base resistance will be evaluated and compared with simulation.
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| 45. |
- Ghandi, Reza, et al.
(author)
-
Removal of Crystal Orientation Effects on the Current Gain of 4H-SiC BJTs Using Surface Passivation
- 2011
-
In: IEEE Electron Device Letters. - : IEEE. - 0741-3106 .- 1558-0563. ; 32:5, s. 596-598
-
Journal article (peer-reviewed)abstract
- In this letter, the dependence of current gain and base resistance on crystal orientations for single-finger 4H-SiC bipolar junction transistors ( BJTs) is analyzed. Statistical evaluation techniques were also applied to study the effect of surface passivation and mobility on the performance of the devices. It is shown that BJTs with an emitter edge aligned to the [1 (2) under bar 10] direction shows a lower current gain before surface passivation and higher base resistance after contact formation compared with other investigated crystal directions. However, the devices show a similar current gain independent of the crystal orientation after surface passivation.
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| 46. |
- Ghandi, Reza, et al.
(author)
-
Surface-passivation effects on the performance of 4H-SiC BJTs
- 2011
-
In: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 58, s. 259-265
-
Journal article (peer-reviewed)abstract
- In this brief, the electrical performance in terms of maximum current gain and breakdown voltage is compared experimentally and by device simulation for 4H-SiC BJTs passivated with different surface-passivation layers. Variation in bipolar junction transistor (BJT) performance has been correlated to densities of interface traps and fixed oxide charge, as evaluated through MOS capacitors. Six different methods were used to fabricate SiO2 surface passivation on BJT samples from the same wafer. The highest current gain was obtained for plasma-deposited SiO2 which was annealed in N2O ambient at 1100 °C for 3 h. Variations in breakdown voltage for different surface passivations were also found, and this was attributed to differences in fixed oxide charge that can affect the optimum dose of the high-voltage junction-termination extension (JTE). The dependence of breakdown voltage on the dose was also evaluated through nonimplanted BJTs with etched JTE.
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| 47. |
- Hallén, Anders, et al.
(author)
-
Low-Temperature Annealing of Radiation-Induced Degradation in 4H-SiC Bipolar Junction Transistors
- 2010
-
In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 31:7, s. 707-709
-
Journal article (peer-reviewed)abstract
- Radiation hardness is tested for 4H-SiC n-p-n bipolar junction transistors designed for 1200-V breakdown voltage by implanting MeV protons and carbon ions at different doses and energies. The current gain is found to be a very sensitive parameter, and a fluence as low as 1 x 107 cm(-2) of 10 MeV C-12 can be clearly detected in the forward-output characteristics, I-C(V-CE). At this low dose, no influence of ion radiation is seen in the open-collector characteristics, I-B(V-EB), or the reverse bias leakage and breakdown properties. Moreover, by annealing the implanted devices at 420 degrees C for 30 min, a complete recovery of the electrical characteristics is accomplished.
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| 48. |
- Hållstedt, Julius, et al.
(author)
-
Hole mobility in ultrathin body SOI pMOSFETs with SiGe or SiGeC channels
- 2006
-
In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 27:6, s. 466-468
-
Journal article (peer-reviewed)abstract
- The hole mobilities of SiGe and SiGeC channel pMOSFETs fabricated on ultrathin silicon-on-insulator substrates are investigated and compared with reference Si channel devices. The total thickness of the fully depleted Si/SiGe(C)/Si body structure is similar to 25 nm. All devices demonstrated a near ideal subthreshold behavior, and the drive current and mobility were increased with more than 60% for SiGe and SiGeC channels. When comparing SIMOX and UNIBOND substrates, no significant difference could be detected.
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| 49. |
- Hållstedt, Julius, et al.
(author)
-
Noise and mobility characteristics of bulk and fully depleted SOI pMOSFETs using Si or SiGe channels
- 2006
-
In: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 3:7, s. 67-72
-
Journal article (peer-reviewed)abstract
- State of the art bulk and fully depleted SOI Si and SiGe channel pMOSFET devices with gate lengths ranging from 0.1 to 200 μm were fabricated and analyzed in terms of drain current drivability, mobility and noise performance. In general the SOI devices demonstrated superior mobility and significantly reduced I/f noise compared to bulk devices maintaining a well controlled short channel effects due to the ultra thin body.
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| 50. |
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