| 1. |
- Berrier, Audrey, et al.
(author)
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Carrier transport through a dry-etched InP-based two-dimensional photonic crystal
- 2007
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:12, s. 123101-1-123101-6
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Journal article (peer-reviewed)abstract
- The electrical conduction across a two-dimensional photonic crystal (PhC) fabricated by Ar/Cl-2 chemically assisted ion beam etching in n-doped InP is influenced by the surface potential of the hole sidewalls, modified by dry etching. Carrier transport across photonic crystal fields with different lattice parameters is investigated. For a given lattice period the PhC resistivity increases with the air fill factor and for a given air fill factor it increases as the lattice period is reduced. The measured current-voltage characteristics show clear ohmic behavior at lower voltages followed by current saturation at higher voltages. This behavior is confirmed by finite element ISE TCAD (TM) simulations. The observed current saturation is attributed to electric-field-induced saturation of the electron drift velocity. From the measured and simulated conductance for the different PhC fields we show that it is possible to determine the sidewall depletion region width and hence the surface potential. We find that at the hole sidewalls the etching induces a Fermi level pinning at about 0.12 eV below the conduction band edge, a value much lower than the bare InP surface potential. The results indicate that for n-InP the volume available for conduction in the etched PhCs approaches the geometrically defined volume as the doping is increased.
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| 2. |
- Berrier, Audrey, et al.
(author)
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Electrical conduction through a 2D InP-based photonic crystal - art. no. 63220J
- 2006
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In: Tuning the Optic Response of Photonic Bandgap Structures III. - : SPIE. - 9780819464019 ; , s. J3220-J3220
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Conference paper (peer-reviewed)abstract
- This work investigates the current transport across two-dimensional PhCs dry etched into InP-based low-index-contrast vertical structures using Ar/Cl-2 chemically assisted ion beam etching. The electrical conduction through the PhC field is influenced by the surface potential at the hole sidewalls, which is modified by dry etching. The measured current-voltage (I-V) characteristics are linear before but show a current saturation at higher voltages. This behaviour is confirmed by simulations performed by ISE-TCAD software. We investigate the dependence of the conductance of the PhC area as a function of the geometry of the photonic crystal as well as the material parameters. By comparing the experimental and simulated conductance of the PhC, we deduce that the Fermi level is pinned at 0.1 eV below the conduction band edge. The method presented here can be used for evaluating etching processes and surface passivation methods. It is also applicable for other material systems and sheds new light on current driven PhC tuning.
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| 3. |
- Buono, Benedetto, et al.
(author)
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Simulations of Open Emitter Breakdown Voltage in SiC BJTs with non Implanted JTE
- 2009
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In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 615-617, s. 841-844
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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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| 4. |
- Danielsson, Erik, et al.
(author)
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A 4H-SiC BJT with an epitaxially regrown extrinsic base layer
- 2005
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In: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 483, s. 905-908
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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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| 5. |
- Domeij, Martin, et al.
(author)
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Analysis of the base current and saturation voltage in 4H-SiC power BJTs
- 2007
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In: 2007 European Conference On Power Electronics And Applications. - 9789075815115 ; , s. 2744-2750
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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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| 6. |
- Domeij, Martin, et al.
(author)
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Current gain dependence on emitter width in 4H-SiC BJTs
- 2006
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In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9780878494255 ; 527-529, s. 1425-1428
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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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| 7. |
- Domeij, Martin, et al.
(author)
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Current gain of 4H-SiC bipolar transistors including the effect of interface states
- 2005
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In: Materials Science Forum. - ZURICH-UETIKON : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 0878499636 ; 483, s. 889-892
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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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| 8. |
- Domeij, Martin, et al.
(author)
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Geometrical effects in high current gain 1100-V 4H-SiC BJTs
- 2005
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In: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 26:10, s. 743-745
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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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| 9. |
- Domeij, Martin, et al.
(author)
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High current gain silicon carbide bipolar power transistors
- 2006
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In: Proceedings of the 18th International Symposium on Power Semiconductor Devices and ICs. ; , s. 141-144
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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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| 10. |
- 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-
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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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