| 1. |
- Choi, J.H., et al.
(författare)
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Comparative study on dry etching of α- and β-SiC nano-pillars
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Scientific.Net. - 9783037856246 ; , s. 817-820
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Konferensbidrag (refereegranskat)abstract
- A comprehensive study on different polytypes (α-SiC and β-SiC) and crystal orientations ((0001) and (11-20) of 6H-SiC) has been investigated in order to elaborate Silicon carbide (SiC) nanopillar using inductively coupled plasma etching method. The SiC nanopillars with the cross section of rhombus, pentagon, and hexagonal have been obtained on β-SiC (001), misoriented α-SiC (11-20), and α-SiC (0001) on-axis substrates, respectively. It was found that crystal orientations and polytypes play key roles for the morphology of SiC nanopillars, which reflects the so-called Wulff's rule.
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| 2. |
- Elahipanah, Hossein, et al.
(författare)
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Process variation tolerant 4H-SiC power devices utilizing trench structures
- 2013
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783037856246 ; 740-742, s. 809-812
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) is one of the most attractive semiconductors for high voltage applications. The breakdown voltage of SiC-based devices highly depends on the variation of the fabrication process including doping of the epilayers and the etching steps. In this paper, we show a way to diminish this variability by employing novel trench structures. The influence of the process variations in terms of doping concentration and etching has been studied and compared with conventional devices. The breakdown voltage variation (ΔVBr) of 450 V and 2100 V is obtained for the ±20% variation of doping concentration of the devices with and without the trench structures, respectively. For ±20% variation in etching steps, the maximum ΔVBR of 380 V is obtained for the device with trench structures in comparison to 1800 V for the conventional structure without trench structures. These results show that the breakdown voltage variation is significantly reduced by utilizing the proposed structure.
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| 3. |
- Henry, Anne, et al.
(författare)
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3C-SiC Heteroepitaxy on Hexagonal SiC Substrates
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications. - 9783037856246 ; , s. 257-262
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Konferensbidrag (refereegranskat)abstract
- The growth of 3C-SiC on hexagonal polytype is addressed and a brief review is given for various growth techniques. The Chemical Vapor Deposition is shown as a suitable technique to grow single domain 3C epilayers on 4H-SiC substrate and a 12.5 µm thick layer is demonstrated; even thicker layers have been obtained. Various characterization techniques including optical microscopy, X-ray techniques and photoluminescence are compared for the evaluation of the crystal quality and purity of the layers.
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| 4. |
- Henry, Anne, et al.
(författare)
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Photoluminescence of 8H-SiC
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications. - 9783037856246 ; , s. 347-350
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Konferensbidrag (refereegranskat)abstract
- 8H-SiC epilayers grown on small 8H-SiC Lely platelets are investigated optically using photoluminescence spectroscopy. At low temperature the near band gap emission detected in the 2.78 to 2.67 eV range contains sharp lines associated to nitrogen-bound-exciton recombination. Three different no-phonon lines are detected accompanied by their phonon replicas. Free-exciton replicas are also observed which allows the determination of the excitonic band gap. The binding energy of the bound excitons can thus be determined and the ionization energies of the three nitrogen levels in 8H-SiC are estimated and found to be rather shallow compared to the values for other hexagonal polytypes. Additional bound-exciton lines are observed when the experimental photoluminescence temperature is increased.
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| 5. |
- Hens, Philip, et al.
(författare)
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Defect generation and annihilation in 3C-SiC-(001) homoepitaxial growth by sublimation
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications. - 9783037856246 ; , s. 283-286
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Konferensbidrag (refereegranskat)abstract
- In this paper we present an investigation on the defect generation and annihilation during the homoepitaxial growth step of cubic silicon carbide by sublimation epitaxy on templates grown by chemical vapor deposition on silicon substrates. Several structural defects like stacking faults, twins and star-defects show opposite evolution from the template layer into the sublimation grown material. While single planar defects tend to annihilate with increasing layer thickness, the defect clusters assigned to the star-defects are enlarging. These issues contribute to a balance of how to achieve the best possible quality on thick layers.
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| 6. |
- Kaiser, M., et al.
(författare)
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Polycrystalline SiC as source material for the growth of fluorescent SiC layers
- 2013
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Ingår i: Silicon Carbide And Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 39-42
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Konferensbidrag (refereegranskat)abstract
- Polycrystalline doped SiC act as source for fluorescent SiC. We have studied the growth of individual grains with different polytypes in the source material. We show an evolution and orientation of grains of different polytypes in polycrystalline SiC ingots grown by the Physical Vapor Transport method. The grain influence on the growth rate of fluorescent SiC layers grown by a sublimation epitaxial process is discussed in respect of surface kinetics.
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| 7. |
- Lanni, Luigia, et al.
(författare)
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High-temperature characterization of 4H-SiC darlington transistors for low voltage applications
- 2013
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783037856246 ; 740-742, s. 966-969
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Tidskriftsartikel (refereegranskat)abstract
- 4H-SiC bipolar Darlington transistors (D-BJTs) for low voltage applications have been fabricated, simulated and characterized up to 300 °C, where they exhibit a current gain of 460. The influence on D-BJT current gain of relative current capability of driver and output BJTs has been investigated, and the collector resistance has been identified as the main limitation for the D-BJTs.
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| 8. |
- Lim, Jang-Kwon, et al.
(författare)
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Modeling of the impact of parameter spread on the switching performance of parallel-connected SiC VJFETs
- 2013
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 1098-1102
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Konferensbidrag (refereegranskat)abstract
- Operation of parallel-connected 4H-SiC VJFETs from SemiSouth was measured and modeled using numerical simulations. The unbalanced current waveforms in parallel-connected VJFETs were related to spread in the critical parameters of the device structure and to the influence of the parasitic inductances in the measurement circuit. The physical device structure was reconstructed based on SEM analysis, electrical characterization, and device simulations. The two hypothetical critical design parameters that were studied with respect to spread were the p-gate doping profile (Case 1) and the emitter doping (Case 2). Variation in both parameters could be related to variation in the emitter breakdown voltage, the on-state characteristics, and the threshold voltage of the experimental devices. The switching performance of the parallel-connected JFETs was measured using a single gate driver in a double pulse test and compared with simulations. In both investigated cases a very good agreement between measurements and simulations was obtained. The modeling of the transient performance relies on good reproduction of transfer characteristics and circuit parasitics.
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| 9. |
- Linnarsson, Margareta K., et al.
(författare)
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Lateral boron distribution in polycrystalline sic source materials
- 2013
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Ingår i: Silicon Carbide And Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 397-400
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Konferensbidrag (refereegranskat)abstract
- Polycrystalline SiC containing boron and nitrogen are used in growth of fluorescent SiC for white LEDs. Two types of doped polycrystalline SiC have been studied in detail with secondary ion mass spectrometry: sintered SiC and poly-SiC prepared by sublimation in a physical vapor transport setup. The materials are co-doped materials with nitrogen and boron to a concentration of 1x1018 cm-3 and 1x1019 cm-3, respectively. Depth profiles as well as ion images have been recorded. According to ocular inspection, the analyzed poly-SiC consists mainly of 4H-SiC and 6H-SiC grains. In these grains, the boron concentration is higher and the nitrogen concentration is lower in the 6H-SiC compared to the 4H-SiC polytype. No inter-diffusion between grains is observed.
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| 10. |
- Nipoti, R., et al.
(författare)
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Al+ implanted 4H-SiC : Improved electrical activation and ohmic contacts
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 767-772
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Konferensbidrag (refereegranskat)abstract
- The p-type doping of high purity semi-insulating 4H-SiC by Al+ ion implantation and a conventional thermal annealing of 1950 °C/5 min has been studied for implanted Al concentration in the range of 1 ×1019 - 8 × 1020 cm-3 and 0.36 um thickness of the implanted layer. Sheet resistance in the range of 1.6 × 104 to 8.9 × 102 ω, corresponding to a resistivity in the range of 4.7 × 10-1 to 2.7 × 10-2 ωcm for increasing Al concentration have been obtained. Hall carrier density and mobility data in the temperature range of 140 - 600 K feature the transition from a valence band to an intra-band conduction for increasing Al concentration. In addition, the specific contact resistance of Ti/Al contacts on the 5 ×1019 cm-3 Al implanted specimen features a thermionic field effect conduction with a specific contact resistance in the 10-6 ωcm2 decade.
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| 11. |
- Ou, Y., et al.
(författare)
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Fabrication of broadband antireflective sub-wavelength structures on fluorescent SiC
- 2013
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Ingår i: Materials Science Forum. - 9783037856246 ; , s. 1024-1027
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Konferensbidrag (refereegranskat)abstract
- Surface nanocones on 6H-SiC have been developed and demonstrated as an effective method of enhancing the light extraction efficiency from fluorescent SiC layers. The surface reflectance, measured from the opposite direction of light emission, over a broad bandwidth range is significantly suppressed from 20.5% to 1.0% after introducing the sub-wavelength structures. An omnidirectional light harvesting enhancement (>91%), is also achieved which promotes fluorescent SiC as a good candidate of wavelength converter for white light-emitting diodes
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| 12. |
- Rabkowski, Jacek, et al.
(författare)
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Evaluation of the drive circuit for a dual gate trench SiC JFET
- 2013
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2012. - : Trans Tech Publications Ltd.. - 9783037856246 ; , s. 946-949
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Konferensbidrag (refereegranskat)abstract
- The paper discusses the switching performance of the dual gate trench SiC JFET. In applications such as dc/dc converters, when fast switching is expected the standard totem-pole driver is not sufficient. The reason for this is that both the internal resistance and the parasitic capacitances of this device are significantly higher than for other designs. Instead, the gate driver with a dynamic current source is proposed in this paper to speed-up the switching process. Performed double-pulse measurements show improved dynamic performance of the tested DGTJFET with the new driver.
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| 13. |
- Salemi, Arash, et al.
(författare)
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Area-optimized JTE simulations for 4.5 kV non ion-implanted sic BJT
- 2013
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783037856246 ; 740-742, s. 974-977
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Tidskriftsartikel (refereegranskat)abstract
- Non ion-implantation mesa etched 4H-SiC BJT with three-zone JTE of optimized lengths and doses (descending sequences) has been simulated. This design presents an efficient electric field distribution along the device. The device area has been optimized and considerably reduced. As a result of this comprehensive optimization, a high breakdown voltage (>6 kV) and high current gain (β=50) have been achieved; meanwhile the device area with a constant emitter and base contact area (300×300 μm2) will be reduced by about 30%.
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| 14. |
- Schimmel, S., et al.
(författare)
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Step-flow growth of fluorescent 4H-SiC layers on 4 degree off-axis substrates
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 185-188
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Konferensbidrag (refereegranskat)abstract
- Homoepitaxial layers of fluorescent 4H-SiC were grown on 4 degree off-axis substrates by sublimation epitaxy. Luminescence in the green spectral range was obtained by co-doping with nitrogen and boron utilizing donor-acceptor pair luminescence. This concept opens possibilities to explore green light emitting diodes using a new materials platform.
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| 15. |
- Sun, Jianwu, et al.
(författare)
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Microsecond carrier lifetimes in bulk-like 3C-SiC grown by sublimation epitaxy
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications. - 9783037856246 ; , s. 315-318
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Konferensbidrag (refereegranskat)abstract
- High quality bulk-like 3C-SiC were grown on on-axis (0001) 6H-SiC substrate by sublimation epitaxy. The microwave photoconductivity decay mapping measurements revealed that this material shows considerable long carrier lifetimes varied from 3.519 to 7.834 mu s under the injection level of 3.5x10(12) cm(-2), which are comparable with the best carrier lifetimes in 4H-SiC layers. The mapping of high resolution x-ray diffraction obtained from the same region shows that smaller carrier lifetimes seem to correspond to the larger FWHM values and vice versa. This shows that long carrier lifetime obtained in 3C-SiC is due to the improvement of the crystal quality.
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| 16. |
- Suvanam, Sethu Saveda, et al.
(författare)
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A comparison of free carrier absorption and capacitance voltage methods for interface trap measurements
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 465-468
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Konferensbidrag (refereegranskat)abstract
- This paper aims to establish a new method to characterize the interface between 4H-SiC and passivating dielectric layers. The investigations are made on MOS test structures utilizing Al2O3 and SiO2 dielectrics on 4H-SiC. These devices are then exposed to various fluences of Ar+ implantation and then measured by the new method utilizing optical free carrier absorption (FCA) technique to assess the interface traps. A program has been developed using Matlab to extract surface recombination velocity (SRV) at the oxide/epi-layer interface from the optical data. Capacitance-voltage (CV) is done to extract the density of interface traps (Dit) and a comparison was made. It is observed that SiO2 samples show a large rise of SRVs, from 0.5×104 cm/s for a reference sample to 8×104 cm/s for a fluence of 1×1012 cm-2, whereas Al2O3 samples show more stable SRV, changing from 3×104 cm/s for the un-irradiated reference sample to 6×104 cm/s for a fluence of 1×1012 cm-2. A very similar trend is observed for Dit values extracted from CV measurements and it can therefore be concluded that the FCA method is a suitable technique for the interface characterization.
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| 17. |
- Tiwari, Amit Kumar, et al.
(författare)
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Transition metal oxide-diamond interfaces for electron emission applications
- 2013
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Ingår i: Silicon carbide and related materials 2012. - Durnten-Zurich : Trans Tech Publications Inc.. - 9783037856246 ; , s. 761-764
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Konferensbidrag (refereegranskat)abstract
- Diamond surfaces with suitable adsorbed chemical species can exhibit both negative and positive electron affinities, arising from the complex electrostatic interplay between adsorbates and surface carbon atoms of diamond lattice. We present the results of density functional calculations into the energetics and the electron affinity of diamond (100) surfaces terminated with the oxides of selected transition metals. We find that for a correct stoichiometry, oxides of transition metals, such as Ti and Zn, exhibit a large negative electronic affinity of around 3 eV. The desorption of transition metal oxides is found to be highly endothermic. We therefore propose that transition metal oxides are promising for the surface coating of diamond-based electron emitters, as these exhibit higher thermal stability in comparison to the commonly used Cs-O termination, while retaining the advantage of inducing a large negative electron affinity
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| 18. |
- ul Hassan, Jawad, et al.
(författare)
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On-axis homoepitaxial growth of 4H-SiC PiN structure for high power applications
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; 740-742, s. 173-176, s. 173-176
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Konferensbidrag (refereegranskat)abstract
- We demonstrate on-axis homoepitaxial growth of 4H-SiC(0001) PiN structure on 3-inch wafers with 100% 4H polytype in the epilayer excluding the edges. The layers were grown with a thickness of 105 μm and controlled n-type doping of 4 x 1014 cm-3.The epilayers were completely free of basal plane dislocations, in-grown stacking faults and other epitaxial defects, as required for 10 kV high power bipolar devices. Some part of the wafer had a lifetime enhancement procedure to increase lifetime to above 2 μs using carbon implantation. An additional step of epilayer polishing was adapted to reduce surface roughness and implantation damage.
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| 19. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Polytype Inclusions in Cubic Silicon Carbide
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications. - 9783037856246 ; , s. 335-338
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Konferensbidrag (refereegranskat)abstract
- In this paper, we review our research on 6H-SiC polytype inclusions in 3C-SiC layers, which were grown on nominally on-axis 6H-SiC substrates using sublimation epitaxy. More than 90% coverage by 3C-SiC is typically achieved at growth temperature of 1775 degrees C. The main reason for the polytype inclusions to appear is local supersaturation non-uniformities over the sample surface which appear due to the temperature gradient and spiral growth nature of 6H-SiC. On the 6H-SiC spirals with small steps supersaturation is smaller and 3C-SiC nucleation and growth is diminished. Due to surface free energy and surface diffusion differences, polytype inclusions appear differently when 3C-SiC is grown on the Si- and C-faces. The 6H-SiC inclusions as well as twin boundaries act as neutral scattering centers and lower charge carrier mobility
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