| 1. |
- Allerstam, Fredrik, 1978, et al.
(author)
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Effect of high temperature oxidation of 4H-SiC on the near-interface traps measured by TDRC
- 2009
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In: Materials Science Forum. - 1662-9752 .- 0255-5476. - 9780878493340 ; 615 617, s. 537-540
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Conference paper (peer-reviewed)abstract
- In this work the effect of oxidation temperature of 4H-SiC on the density of nearinterface traps is studied. It is seen that the portion of traps with slower emission times decreases with increasing oxidation temperature. Despite this reduction, high temperature oxidation alone is not useful to achieve low density of interface traps at the SiO2/4H-SiC interface.
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| 2. |
- Beshkova, Milena, 1975-, et al.
(author)
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Structural Properties of 3C-SiC Grown by Sublimation Epitaxy
- 2009
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In: ECSCRM2009,2009. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 181-184
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Conference paper (peer-reviewed)abstract
- The present paper deals with morphological and structural investigation of 3C-SiC layers grown by sublimation epitaxy on on axis 6H-SiC(0001) at source temperature 2000 °C, under vacuum conditions (<10-5 mbar) and different temperature gradients in the range of 5-8 °C/mm. The layer grown at a temperature gradient 6 °C/mm has the largest average domain size of 0.4 mm2 assessed by optical microscope in transmission mode. The rocking curve full width at half maximum (FWHM) of (111) reflection is 43 arcsec which suggests good crystalline quality. The AFM image of the same layer shows steps with height 0.25 nm and 0.75 nm which are characteristic of a stacking fault free 3C-SiC surface and c-axis repeat height, respectively.
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| 3. |
- Carlsson, Patrick, 1975-, et al.
(author)
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Photo-EPR Studies on Low-Energy Electron-irradiated 4H-SiC
- 2009
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In: Materials Science Forum, Vols. 615-617. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 401-404
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Conference paper (peer-reviewed)abstract
- Photoexcitation electron paramagnetic resonance (photo-EPR) was used to determine deep levels related to the carbon vacancy (VC) in 4H-SiC. High-purity free-standing n-type 4H-SiC epilayers with concentration of intrinsic defects (except the photo-insensitive SI1 center) below the detection limit of EPR were irradiated with low-energy (200 keV) electrons to create mainly VC and defects related to the C sublattice. The simultaneous observation of and signals, their relative intensity changes and the absence of other defects in the sample provide a more straight and reliable interpretation of the photo-EPR results. The study suggests that the (+|0) level of VC is located at ~EC–1.77 eV in agreement with previously reported results and its single and double acceptor levels may be at ~ EC–0.8 eV and ~ EC–1.0 eV, respectively.
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| 4. |
- Ghandi, Reza, et al.
(author)
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Implantation-Free Low on-resistance 4H-SiC BJTs with Common-Emitter Current Gain of 50 and High Blocking Capability
- 2009
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In: Materials Science Forum. - STAFA-ZURICH : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9780878493340 ; 615-617, s. 833-836
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Journal article (peer-reviewed)abstract
- In this study, high voltage blocking (2.7 kV) implantation-free SiC Bipolar Junction Transistors with low on-state resistance (12 m Omega-cm(2)) and high common-emitter current gain of 50 have been fabricated. A graded base doping was implemented to provide a low resistive ohmic contact to the epitaxial base. This design features a fully depleted base layer close to the breakdown voltage providing an efficient epitaxial JTE without ion implantation. Eliminating all ion implantation steps in this approach is beneficial for avoiding high temperature dopant activation annealing and for avoiding generation of life-time killing defects that reduces the current gain. Also in this process large area transistors showed common-emitter current gain of 38 and open-base breakdown voltage of 2 kV.
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| 5. |
- Henry, Anne, 1959-, et al.
(author)
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Growth of 4H-SiC Epitaxial Layers on 4° Off-axis Si-face substrates
- 2009
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In: Materials Science Forum, Vols. 615-617. - : Trans Tech Publications. - 9780878493340 ; , s. 81-84
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Conference paper (peer-reviewed)abstract
- CVD growth of epitaxial layers with a mirror like surface grown on 75 mm diameter 4° off-axis 4H SiC substrates is demonstrated. The effect of the C/Si ratio, temperature and temperature ramp up conditions is studied in detail. A low C/Si ratio of 0.4 and a temperature of 1530 °C is the best combination to avoid step bunching and triangular defects on the epitaxial layers. Using a low growth rate (about 3 µm/h) 6 μm thick, n-type doped epilayers were grown on 75 mm diameter wafers resulting in an RMS value of 0.7 nm and good reproducibility. 20 μm thick epitaxial layers with a background doping in the low 1014 cm-3 were grown with a mirror-like, defect-free surface. Preliminary results when using higher Si/H2 ratio (up to 0.4 %) and HCl addition are also presented: growth rate of 28 μm/h is achieved while keeping a smooth morphology.
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| 6. |
- Henry, Anne, 1959-, et al.
(author)
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Single Crystal and Polycrystalline 3C-SiC for MEMS Applications
- 2009
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In: Materials Science Forum Vols. 615-617. - : Trans Tech Publications. - 9780878493340 ; , s. 625-628
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Conference paper (peer-reviewed)abstract
- Cantilever resonators have been fabricated from two types of materials, single crystal and polycrystalline 3C-SiC films. The films have been grown in a hot-wall chemical vapor deposition reactor on 100 mm diameter p-type boron-doped (100) Si wafer without rotation of the wafer. The crystal structure of the films have been accessed with X-ray diffraction. The cantilever devices have been fabricated using a one-step etch and release process; the beam length has been varied between 50 and 200 µm. Resonant frequencies in the range 110 KHz – 1.5 MHz and 50 – 750 KHz have been obtained for single crystal and polycrystalline SiC devices, respectively. Furthermore, the experimental resonance frequencies have been used to calculate the Young’s Modulus E for the two different types of SiC. The single crystal SiC, possessing a very high Young’s Modulus (446 GPa), should be an optimal material for RF-MEMS applications.
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| 7. |
- Hens, Philip, et al.
(author)
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P- and n-type doping in SiC sublimation epitaxy using highly doped substrates
- 2009
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In: ECSCRM2008,2008. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 85-88
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Conference paper (peer-reviewed)abstract
- The co-doping of nitrogen and aluminum has been studied in the sublimation epitaxy growth process. It is shown that the doping may be tuned from n-type to p-type by effect of substrate doping, growth face and volume of the growth crucible. The co-doped layers show a nearly ideal I V characteristic and luminescence at room temperature.
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| 8. |
- Ivanov, Ivan Gueorguiev, 1955-, et al.
(author)
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Temperature Dependence and Selective Excitation of the Phosphorus Related Photoluminescence in 4H-SiC
- 2009
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In: Materials Science Forum, Vols. 615-617. - : Trans Tech Publications. - 9780878493340 ; , s. 263-266
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Conference paper (peer-reviewed)abstract
- The paper presents experimental data on the temperature dependence and the excitation properties of the phosphorus-related photoluminescence in 4H SiC. Two main sets of phonon replicas can be observed with selective excitation, which are attributed to two of the no-phonon lines observed in the spectrum. Some of the excited states are also attributed to one of the no-phonon lines on the ground of the selectively excited spectra. A tentative explanation of the observed features in terms of multiple bound excitons is proposed.
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| 9. |
- Lebedev, S.P., et al.
(author)
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P-type 3C-SiC Grown by Sublimation Epitaxy on 6H-SiC Substrates
- 2009
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In: ECSCRM2008,2008. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 177-180
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Conference paper (peer-reviewed)abstract
- Highly doped p-3C-SiC layers of good crystal perfection have been grown by sublimation epitaxy in vacuum. Analysis of the photoluminescence (PL) spectra and temperature dependence of the carrier concentration shows that at least two types of acceptor centers at ~EV + 0.25 eV and at EV + 0.06-0.07 eV exist in the samples studied. A conclusion is made that layers of this kind can be used as p-emitters in 3C-SiC devices.
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| 10. |
- Nguyen, Son Tien, 1953-, et al.
(author)
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Defects introduced by electron-irradiation at low temperatures in SiC
- 2009
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In: Materials Science Forum Vols. 615-617. - : Trans Tech Publicarions. - 9780878493340 ; , s. 377-380
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Conference paper (peer-reviewed)abstract
- Defects introduced by electron irradiation at ~80-100 K in 3C-, 4H- and 6H-SiC were studied by electron paramagnetic resonance (EPR). A number of EPR spectra, labelled LE1-10, were detected. Combining EPR and supercell calculations, we will show that the LE1 center in 3C-SiC with C2v symmetry and an electron spin S=3/2 is related to the (VSi-Sii)3+ Frenkel pair between the silicon vacancy and a second neighbour Sii interstitial along the <100> direction. Results on other centers, possibly also related to interstitials, are discussed.
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| 11. |
- Palisaitis, Justinas, 1983-, et al.
(author)
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Two Dimensional X-ray Diffraction Mapping of Basal Plane Orientation on SiC Substrates
- 2009
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In: ECSCRM2008,2009. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 275-278
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Conference paper (peer-reviewed)abstract
- We have performed 2D X-ray diffraction mapping of the SiC lattice basal plane orientation over full 2” SiC substrates. Measurements of the omega angle were made in two perpendicular directions <11-20> and <1-100>, which gives the complete vectorized tilt of the basal planes. The Mapping revealed two characteristic bending behaviors on measured commercial wafers. The first is characterized by large variations in omega angle across the wafer in both crystallographic directions. The continuously changing omega angle in both directions gives the wafer an apparent rotationally symmetric bending which is concave towards the growth direction. The second characteristic behavior is seen in wafers with lower degree of omega angle variation. The variations in this type of wafers are not changing linearly, but are bending the basal planes with two-fold symmetry.
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| 12. |
- Sankin, V.I., et al.
(author)
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Features of hot hole transport in 6H-SiC
- 2009
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In: ECSCRM2008,2008. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 307-310
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Conference paper (peer-reviewed)abstract
- In materials with a small degree of ionicity ranging 10-15%, such as in SiC, carrier scattering on polar optical potential is possible. Unlike scattering on deformation potential, the drift mobility in this case increases continuously. As this phenomenon may be realized in SiC hot hole transport, I-F characteristics in 6H-SiC with Na-Nd ~ 5x1017 cm-3 have been studied at electrical field 1-150 kV/cm for temperature from 300 to 600K. Furthermore, we studied the breakdown of Al impurity.
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| 13. |
- ul-Hassan, Jawad, 1974-, et al.
(author)
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Influence of Structural defects on Carrier Lifetime in 4H Epitaxial Layers, Studied by High Resolution Optical Lifetime Mapping
- 2009
-
In: ECSCRM2008,2008. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 255-258
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Conference paper (peer-reviewed)abstract
- Thick 4H-SiC epitaxial layers have been characterized using high-resolution lifetime mapping. The lifetime maps are obtain by the detection of photoluminescence decay of the band gap emission. Full wafers mappings with 200 m resolution reveal lifetime variations that can be associated with structural defects replicated from the substrate, and variations in epitaxial growth conditions due to the susceptor design. High resolution mapping over smaller regions with down to 20 m step size, reveals local lifetime reductions associated with different structural defects in the epitaxial layer. Identified defects that influence the lifetime are the carrot defect, different types of in-grown stacking faults, and an unidentified defect associated with a pair of basal plane dislocations on the surface. Also clusters of threading screw dislocations, probably originating from a dissociated micropipe in the substrate, are found to reduce the lifetime.
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| 14. |
- ul-Hassan, Jawad, 1974-, et al.
(author)
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On-axis Homoepitaxy on Full 2- 4H-SiC Wafer for High Power Applications
- 2009
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In: Materials Science Forum Vols. 615-617. - : Trans Tech Publications. - 9780878493340 ; , s. 133-136
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Conference paper (peer-reviewed)abstract
- Homoepitaxial growth has been performed on Si-face nominally on-axis 4H-SiC substrates. Special attention was paid to the surface preparation before starting the growth. Si-face polished surfaces were studied after etching under C-rich, Si-rich and under pure hydrogen ambient conditions. In-situ surface preparation, starting growth parameters and growth temperature are found to play a vital role to maintain the polytype stability in the epilayer. High quality epilayers with 100% 4H-SiC were obtained on full 2” wafer. Complete PiN structure was grown and more than 70% of the diodes showed a stable behavior and the forward voltage drift was less than 0.1 V. Also, a comparison of the electroluminescence images of diodes before and after heavy injection of 125 A/cm2 for 30 min did not show any sign of stacking fault formation in the device active region.
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| 15. |
- Vasiliauskas, Remigijus, 1982-, et al.
(author)
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Two-dimensional nucleation of cubic and 6H silicon carbide
- 2009
-
In: ECSCRM2008,2008. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 189-192
-
Conference paper (peer-reviewed)abstract
- The initial stage of heteroepitaxial growth of 3C-SiC and homoepitaxial growth of 6H-SiC on nominal 6H-SiC on-axis substrates has been studied. Before 3C-SiC starts to nucleate, 6H-SiC grows in a step-flow growth mode due to a slight off-orientation of the substrate surface already at about 1500oC. In the 1650-1700oC temperature interval 3C-SiC nucleates as 2D islands. A distance away from the 3C-SiC island 6H-SiC grows in step-flow mechanism. In the vicinity of the 3C-SiC islands the 6H-SiC growth steps start to change direction and even split into two steps with the equal height of 0.5 nm, which is approaching the unit cell size of cubic SiC. When the supersaturation is lower in comparison with the conditions for 3C-SiC growth, there is only formation of 6H-SiC, i.e. homoepitaxial growth. The growth mode of 6H-SiC is dependent on temperature. At the lowest temperature there is spiral growth while at higher temperature 2D nucleation is preferred.
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