| 1. |
- Danielson, E., et al.
(författare)
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Investigation of thermal properties in fabricated 4H-SiC high power bipolar transistors
- 2003
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Ingår i: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 47:4, s. 639-644
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Danielsson, Erik, et al.
(författare)
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Investigation of thermal properties in fabricated 4H-SiC high-power bipolar transistors
- 2002
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 389-393:2, s. 1337-1340
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Tidskriftsartikel (refereegranskat)abstract
- Silicon Carbide bipolar junction transistors have been fabricated and investigated. The transistors had a maximmn current gain of approximately 10 times, and a breakdown voltage of up to 600 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 °C, 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. Physical device simulations have been used to analyze the measured data. The thermal conductivity is fitted to model the measured self-heating, and the lifetime in the base is fitted against the measurement of the current gain.
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| 3. |
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| 4. |
- Koo, S. -M, et al.
(författare)
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Influence of trenching effect on the characteristics of buried-gate SiC junction field-effect transistors
- 2002
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 389-393:2, s. 1235-1238
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Tidskriftsartikel (refereegranskat)abstract
- Two different structures of junction field-effect transistors in 4H-SiC, with and without trenching effect in the channel region, have been fabricated and characterized. The devices formed with metal mask show a trenching profile (>∌0.2 Όm) after dry etch in the channel groove region and exhibited static induction transistor (SIT)-like characteristics in the sub-threshold region of I-V curves as the channel thickness decreases. The devices without trenching effect have been processed by using a wet-etched oxide mask resulting in a sloped dry-etch profile (Ξ=∌30°) in the channel, and consequently showed well-saturated drain characteristics for all the channel thicknesses. The conduction mechanisms in these JFETs are examined by the potential profiles from two dimensional numerical simulations.
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| 5. |
- Koo, S. -M, et al.
(författare)
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Simulation and Measurement of Switching Characteristics of 4H-SiC Buried-Gate JFETs
- 2003
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 433-436, s. 773-776
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Tidskriftsartikel (refereegranskat)abstract
- Buried-gate junction field-effect transistors (JFETs) have been fabricated in 4H polytype silicon carbide (SiC). The dynamic switching characteristics of the JFETs in a circuit with inductive load have been characterized. The drain voltage rise/fall time of ∌30 ns and 25 ns have been observed for turn-off and turn-on, respectively. The results have been compared to numerical mixed-mode circuit simulations with finite element structures.
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| 9. |
- Köhler, Jan, et al.
(författare)
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Long-term effects of reflux nephropathy on blood pressure and renal function in adults.
- 2003
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Ingår i: Nephron Clinical Practice. - : S. Karger AG. - 1660-2110. ; 93:1, s. 35-46
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Tidskriftsartikel (refereegranskat)abstract
- <i>Aims:</i> We investigated whether the grade of renal damage assessed by urography in adult patients with vesicoureteral reflux can be used to identify patients at risk of developing hypertension and/or deterioration of renal function. In addition, maternal and fetal outcome of pregnancy was studied. <i>Methods:</i> Vesicoureteral reflux was diagnosed at a median age of 27 years (range 16–60) in 115 patients (98 women). Excluding patients subjected to nephrectomy or heminephrectomy after inclusion (n = 12), 88 patients had renal damage at inclusion urography and a median follow-up time of 16 years. The median follow-up time was 18 years in 15 patients without renal damage. Grading of renal damage was performed and blood pressure, serum creatinine concentration and albuminuria were measured. Hypertension was considered to be present if the systolic blood pressure was ≧140 mm Hg and/or the diastolic blood pressure was ≧90 mm Hg. It was classified as mild (<180 mm Hg systolic and <105 mm Hg diastolic), or moderate to severe (≧180 mm Hg systolic and/or ≧105 mm Hg diastolic). Renal function was classified as stable or deteriorating. <i>Results:</i> There was no significant difference in the frequency of hypertension among those with (52%) or without (33%) renal damage, but moderate to severe hypertension (16 patients) was only seen in patients with renal damage. Median systolic and diastolic blood pressure were higher in patients with than in those without renal damage. Malignant hypertension developed in 4 patients, all had extensive renal damage. Deterioration of renal function occurred in 25 patients, 1 with unilateral and 24 with extensive renal damage (bilateral or in a solitary kidney). This was associated with a high frequency of hypertension (92%) and albuminuria (88%). Sixteen patients developed end-stage renal disease. A total of 242 pregnancies occurred in 89 of the 98 women. Preeclampsia occurred in 16 (18%) women. <i>Conclusion:</i> Hypertension in adult patients with reflux nephropathy occurs with any grade of renal damage, whereas deterioration of renal function was strongly associated with extensive bilateral renal damage or damage in a solitary kidney.
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