| 1. |
- Ellison, A., et al.
(författare)
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Epitaxial growth of SiC in a chimney CVD reactor
- 2002
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 236:1-3, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- A high growth rate (>10 µm/h) Chemical Vapour Deposition (CVD) process is investigated in a vertical hot-wall, or "chimney", reactor. By the use of increased temperatures (1650-1850°C) and concentrations of reactants, this process is shown to enable growth rates up to 50µm/h and demonstrates a material quality comparable to established CVD techniques until growth rates of 25 µm/h. The gas flow dynamics, the growth rate and the thickness uniformity determining steps are investigated, and the role of homogenous nucleation is analysed. The growth rate is shown to be influenced by two competing processes: the supply of growth species and the etching of the hydrogen carrier gas. The exponential increase of the growth rate with temperature is related to a Si-vapour release from clusters homogeneously nucleated in the inlet of the susceptor and acting as a growth species reservoir. © 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Ellison, A, et al.
(författare)
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Fast SiC epitaxial growth in a chimney CVD reactor and HTCVD crystal growth developments
- 2000
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Ingår i: Materials science Forum, Vols. 338-342. - : Trans Tech Publications Inc.. - 0878498540 ; , s. 131-136
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Konferensbidrag (refereegranskat)abstract
- The epitaxial growth of SiC is investigated in a CVD process based on a vertical hot-wall, or "chimney", reactor geometry. Carried out at increased temperatures (1650 to 1850 degreesC) and concentrations of reactants, the growth process enables epitaxial rates ranging from 10 to 50 mum/h. The growth rate is shown to be influenced by two competing processes: the supply of growth species in the presence of homogeneous gas-phase nucleation, and, the etching effect of the hydrogen carrier gas. The quality of thick (20 to 100 mum) low-doped 4H-SiC epitaxial layers grown at rates ranging between 10 and 25 mum/h are discussed in terms of thickness uniformity, surface morphology and purity. The feasibility of high voltage Schottky rectifiers (V-BR from 2 to similar to3.8 kV) on as-grown chimney CVD epilayers is reported. In a second part, recent developments of the High Temperature Chemical Vapor Deposition (HTCVD) technique for SiC crystal growth are described. Using pure gases (SiH4 and C2H4) as source material and growth temperatures of 2100-2300 degreesC, this technique enables at present growth rates ranging from 0.4 to 0.8 mm/h. 6H and 4H-SiC crystals of thickness up to 7 mm and diameters up to 40 mm have been grown. We report micropipe densities of similar to 80 cm(-2) over areas of 0.5 cm(2) in 35 mm diameter 4H-SiC wafers sliced from HTCVD grown crystals. Undoped wafer demonstrators exhibit semi-insulating behavior with a bulk resistivity higher than 7.10(9) Omega cm at room temperature.
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| 3. |
- Ivanov, Ivan Gueorguiev, et al.
(författare)
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Intrinsic photoconductivity of 6H-SiC and the free-exciton binding energy
- 2001
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Ingår i: Materials Science Forum, Vols. 353-356. ; , s. 405-408
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Konferensbidrag (refereegranskat)abstract
- The paper presents a study of the low-temperature photoconductivity of 6H-SiC. The photocurrent at the absorption edge is assigned to Auger recombination of excitons captured to impurities. This is shown to saturate and decrease with increasing the photon energy, so the further increase in the photocurrent, observed in the purest sample, can be attributed to free excitons created in non-bound states in the exciton continuum. Thus, the exciton binding energy can be estimated, E-bx approximate to 60 +/- 5 meV in 6H-SiC.
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| 4. |
- Wahab, Qamar Ul, et al.
(författare)
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Designing, physical simulation and fabrication of high-voltage (3.85 kV) 4H-SiC Schottky rectifiers processed on hot-wall and chimney CVD films
- 2000
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Ingår i: Materials Science Forum, Vols. 338-342. ; , s. 1171-1174
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Konferensbidrag (refereegranskat)abstract
- Physical simulation, fabrication and characterization of high-voltage Ni/4H-SiC Schottky rectifiers are studied. We demonstrate a blocking voltage of 3.85 kV by utilizing a 43 mum thick low doped 4H-SiC epilayer in vertical hot-wall Chimney CVD reactor. A high breakdown voltage of 3.56 kV was achieved on a layer grown by conventional hot-wall CVD reactor. The reverse leakage current on CVD sample was as low as 5 x 10(-6) A cm(-2) at 3.5 kV just before the breakdown.
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| 5. |
- Wahab, Qamar Ul, et al.
(författare)
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Influence of epitaxial growth and substrate-induced defects on the breakdown of 4H-SiC Schottky diodes
- 2000
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Ingår i: Applied Physics Letters. - 0003-6951 .- 1077-3118. ; 76:19, s. 2725-2727
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Tidskriftsartikel (refereegranskat)abstract
- Morphological defects and elementary screw dislocations in 4H-SiC were studied by high voltage Ni Schottky diodes. Micropipes were found to severely limit the performance of 4H-SiC power devices, whereas carrot-like defects did not influence the value of breakdown voltage. The screw dislocation density as determined by x-ray topography analysis under the active area of the diode was also found to directly affect the breakdown voltage. Only diodes with low density of screw dislocations and free from micropipes could block 2 kV or higher. (C) 2000 American Institute of Physics. [S0003-6951(00)01119-0].
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| 6. |
- Wahab, Qamar Ul, et al.
(författare)
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Influence of epitaxial growth and substrate induced defects on the breakdown of high-voltage 4H-SiC Schottky diodes
- 2000
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Ingår i: Materials Science Forum(ISSN 0255-5476), Volume 338-3. - : Scientific.Net. - 0878498540 ; , s. 1175-1178
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Konferensbidrag (refereegranskat)abstract
- The influence of morphological and structural defects on high-voltage 4H-SiC Schottky diodes was studied. Micropipes were found as severely limiting the breakdown voltage of 4H-SiC power devices, where as carrot-like defects did not influence the value of breakdown voltage. The screw dislocation density as determined by X-ray topography analysis under the active area of the diode was also found to directly affect the breakdown voltage value. Only diodes with low density of screw dislocations and free from micropipes could block 2 kV or higher.
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| 7. |
- Zhang, J, et al.
(författare)
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Epitaxial growth of 4H-SiC in a vertical hot-wall CVD reactor : Comparison between up- and down-flow orientations
- 2001
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Ingår i: Materials Science Forum, Vols. 353-356. - : Trans Tech Publications. ; , s. 91-94
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Konferensbidrag (refereegranskat)abstract
- The effect of reactor orientation on the CVD growth of JH SIC is investigated. Compared with the up-flow orientation (the chimney reactor), the down-flow orientation (the inverted chimney) shows similar growth rate dependencies on C/Si ratio and pressure. The activation energy of the growth rate in the inverted chimney is Lower than that in the chimney. The inverted chimney also produces epilayers with high growth rates (10 - 30 mum/h) and low residual doping (low 10(16) down to mid 10(13) cm(-3)). The epilayer morphology is comparable with that of the chimney samples. A qualitative analysis is performed on the heat transfer mechanisms in these two reactor orientations in terms of dimensionless flow numbers.
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| 8. |
- Zhang, J, et al.
(författare)
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Growth characteristics of SiC in a hot-wall CVD reactor with rotation
- 2002
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Ingår i: Materials Science Forum(ISSN 0255-5476) Volume 389-3. ; , s. 191-194
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Konferensbidrag (refereegranskat)abstract
- SiC epitaxy has been studied in a horizontal hot-wall CVD reactor with rotation by gas foil levitation. A capacity of three 2 inch wafers has been realized, and the thickness uniformity over a 2 inch wafer is below 1% and the n-doping uniformity over a 35mm wafer, below 10%. Both n- and p-type doping is readily achieved with no memory effect. The layer morphology has been investigated and a featureless surface has been obtained through process optimization and a modification of the hot zone.
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| 9. |
- Zhang, J., et al.
(författare)
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Growth characteristics of SiC in a hot-wall CVD reactor with rotation
- 2002
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 241:4, s. 431-438
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Tidskriftsartikel (refereegranskat)abstract
- A version of the hot-wall reactor, where rotation has been added is investigated for the growth of SiC. The capacity of the reactor is 2 in wafers. The rotation is realized by gas foil levitation of a single plate carrying all three wafers. Uniformities of thickness and doping below 1% and 5%, respectively have been obtained. The run to run reproducibility of n-type doping is within ±10%. The morphology is studied and greatly improved through a modification of the hot-zone, which however made the thickness uniformity marginally worse. © 2002 Published by Elsevier Science B.V.
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| 10. |
- Zhang, J, et al.
(författare)
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In situ etching of 4H-SiC in H-2 with addition of HCl for epitaxial CVD growth
- 2002
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Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 239-242
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Konferensbidrag (refereegranskat)abstract
- We have investigated in situ etching of 4H SiC in a horizontal hot-wall CVD reactor. A small amount of HCl is introduced together with the major etching gas, H-2. The etch rate is found to increase with temperature and decrease with pressure. An increased H-2 flow proportionally increases the etch rate. The etch mechanism is proposed from the etch rate dependencies on the etch parameters. The morphology both after the etch and after the subsequent growth is investigated and the optimized etch conditions for good morphology are established. The correlation between the morphology and the etch mechanism is pointed out.
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