| 11. |
- Ciechonski, Rafal, et al.
(författare)
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Effect of Ambient on 4H-SiC Bulk Crystals grown by Sublimation
- 2003
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Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 75-78
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Konferensbidrag (refereegranskat)abstract
- Sublimation bulk growth in vacuum using graphite crucibles and such with tantalum shielding of the crucible walls has been studied. Residual nitrogen, aluminum and boron doping in the material grown in vacuum is presented. Activation energies of growth rate in respect to growth temperature in vacuum are deduced. The estimated values are 21 kcallmole for growth temperatures below 2075°C and 128 kcal/mole in the range of growth temperatures between 2075°C and 2275°C. Cathodoluminescence spectra taken from samples grown in the graphite crucible in absence of tantalum under different pressures show nitrogen-alurninum DAP transition and strong luminescence from deep boron. This is not the case for samples grown in the tantalum environment.
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| 12. |
- Ciechonski, Rafal, et al.
(författare)
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Effect of boron on the resistivity of compensated 4H-SiC
- 2003
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Ingår i: Journal of electronic materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 32:5, s. 452-457
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Tidskriftsartikel (refereegranskat)abstract
- High-resistivity 4H-SiC samples grown by sublimation with a high growth rate are studied. The measurements show resistivity values up to a high of 104 Ωcm. The secondary ion mass spectroscopy (SIMS) results revealed a presence of only common trace impurities such as nitrogen, aluminum, and boron. To understand the compensation mechanism in these samples, capacitance deep-level transient spectroscopy (DLTS) on the p-type epilayers has been performed. By correlation between the growth conditions and SIMS results, we apply a model in which it is proposed that an isolated carbon vacancy donorlike level is a possible candidate responsible for compensation of the shallow acceptors in p-type 4H-SiC. A relation between cathodoluminescence (CL) and DLTS data is taken into account to support the model.
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| 13. |
- Ciechonski, Rafal, 1976-, et al.
(författare)
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Evaluation of MOS structures processed on 4H–SiC layers grown by PVT epitaxy
- 2005
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Ingår i: Solid-State Electronics. - : Elsevier BV. - 0038-1101 .- 1879-2405. ; 49:12, s. 1917-1920
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Tidskriftsartikel (refereegranskat)abstract
- MOS capacitors have been fabricated on 4H–SiC epilayers grown by physical vapor transport (PVT) epitaxy. The properties were compared with those on similar structures based on chemical vapor deposition (CVD) layers. Capacitance–voltage (C–V) and conductance measurements (G–V) were performed in the frequency range of 1 kHz to 1 MHz and also at temperatures up to 475 K. Detailed investigations of the PVT structures indicate a stable behaviour of the interface traps from room temperature up to 475 K. The amount of positive oxide charge QO is 6.83 × 109 cm−2 at room temperature and decreases with temperature increase. This suggests that the processed devices are temperature stable. The density of interface states Dit obtained by Nicollian–Brews conductance method is lower in the structure based on the PVT grown sample.
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| 14. |
- Ciechonski, Rafal, et al.
(författare)
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Evaluation of On-state Resistance and Boron-related Levels in n-type 4H-SiC
- 2005
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Ingår i: Materials Science Forum, Vols. 483-485. ; , s. 425-428
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Konferensbidrag (refereegranskat)abstract
- Specific on-resistance Ron estimated from current density-voltage characteristics of Schottky diodes on thick layers exhibits variations from tens of mΩ.cm2 to tens of Ω.cm2 for different doping levels. In order to understand the occurrence of high on-state resistance, Schottky barrier heights were first estimated for both forward and reverse bias with the application of thermionic emission theory and were in agreement with a literature reported values. Decrease in mobility with the temperature was observed and its dependencies of T–1.3 and T–2.0 for moderately doped and low doped samples respectively were estimated. From deep level measurements by Minority Carrier Transient Spectroscopy, an influence of shallow boron related levels and D-center on dependence of on-state resistance was observed, being more pronounced in low doped samples. Similar tendency was observed in depth profiling of Ron. This suggests a major role of boron in a compensation mechanism thus resulting in high Ron.
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| 15. |
- Ciechonski, Rafal, et al.
(författare)
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Structural instabilities in growth of SiC crystals
- 2005
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 275:1-2, s. e461-e466
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Tidskriftsartikel (refereegranskat)abstract
- Misoriented grains, which may occur on the growth front of 6H–SiC boules have been studied in relation to their appearance during sublimation growth. The effect was obtained by applying growth conditions at which the source powder was gradually approaching graphitisation and the vapour becoming C-rich. The high off-orientation of the grains is demonstrated through etching in molten KOH and transmission light optical microscopy. Micropipes propagating in the single crystal area and facing the misoriented grain have been studied, and it is shown that they may either be terminated at the grain or their propagation is altered to be parallel with the grain boundary. It has been found that the polytype of the grains may switch from 6H to 4H, which is explained by the change of the Si/C ratio in the vapour.
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| 16. |
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| 17. |
- Dannefaer, S, et al.
(författare)
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Vacancies in As-grown and electron-irradiated 4H-SiC epilayers investigated by positron annihilation
- 2003
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Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 173-176
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Konferensbidrag (refereegranskat)abstract
- Epilayers of 4H-SiC were investigated by positron annihilation spectroscopies: four epilayers and their substrates were investigated. The epilayers (47 to 220 mum thick) contained significantly lower grown-in vacancy concentration than did their substrates, and there was no dependency on layer thickness. Upon electron irradiation silicon vacancies were introduced at the same rate in epilayer and in substrate.
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| 18. |
- Davydov, SY, et al.
(författare)
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Simple model for calculation of SiC epitaxial layers growth rate in vacuum.
- 2004
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Ingår i: Materials Science Forum, Vols. 457-460. ; , s. 249-252
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Konferensbidrag (refereegranskat)abstract
- Within the frame of a simple model, based on Hertz-Knudsen equation with account of temperature dependant sticking coefficient, temperature dependence of silicon carbide epitaxial layers growth rate in vacuum has been calculated. Calculation results are in a good agreement with the experimental data.
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| 19. |
- Davydov, S.Yu., et al.
(författare)
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A Simple Model for Calculating the Growth Rate of Epitaxial Layers of Silicon Carbide in Vacuum
- 2004
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Ingår i: Semiconductors (Woodbury, N.Y.). - : American Institute of Physics (AIP). - 1063-7826 .- 1090-6479. ; 38:2, s. 150-152
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependence of the growth rate of epitaxial layers of silicon carbide in vacuum was calculated within the simple model based on the Hertz-Knudsen equation, taking into account the temperature-dependent sticking coefficient. The calculation results fit the experimental data well. © 2004 MAIK "Nauka/Interperiodica".
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| 20. |
- Eriksson, Jens, et al.
(författare)
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The influence of substrate morphology on thickness uniformity and unintentional doping of epitaxial graphene on SiC
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:24, s. 241607-
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Tidskriftsartikel (refereegranskat)abstract
- A pivotal issue for the fabrication of electronic devices on epitaxial graphene on SiC is controlling the number of layers and reducing localized thickness inhomogeneities. Of equal importance is to understand what governs the unintentional doping of the graphene from the substrate. The influence of substrate surface topography on these two issues was studied by work function measurements and local surface potential mapping. The carrier concentration and the uniformity of epitaxial graphene samples grown under identical conditions and on substrates of nominally identical orientation were both found to depend strongly on the terrace width of the SiC substrate after growth.
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