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| 2. |
- Gällström, Andreas, 1978-, et al.
(författare)
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Influence of Cooling Rate after High Temperature Annealing on Deep Levels in High-Purity Semi-Insulating 4H-SiC
- 2007
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Ingår i: Materials Science Forum, vol. 556-557. - : Trans Tech Publications. ; , s. 371-
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Konferensbidrag (refereegranskat)abstract
- The influence of different cooling rates on deep levels in 4H-SiC after high temperature annealing has been investigated. The samples were heated from room temperature to 2300°C, followed by a 20 minutes anneal at this temperature. Different subsequent cooling sequences down to 1100°C were used. The samples have been investigated using photoluminescence (PL) and IV characteristics. The PL intensities of the silicon vacancy (VSi) and UD-2, were found to increase with a faster cooling rate.
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| 3. |
- Gällström, Andreas, 1978-, et al.
(författare)
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Optical identification of Mo related deep level defect in 4H and 6H SiC
- 2009
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Ingår i: Materials Science Forum Vols. 615-617. - : Trans Tech Publications. ; , s. 405-408
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Konferensbidrag (refereegranskat)abstract
- The photoluminescence (PL) from the I 1 centre is observed in p-, n-type as well as in compensated samples, using above band gap excitation. The PL from I 1 in the two polytypes 4H and 6H is very similar, the difference being the position of the main peak, in 4H 1.1521 eV and 1.1057 eV in 6H. We here suggest I-1 to be Mo related based on intentional doping, SIMS results and comparison with earlier reports of Mo in SiC using magnetic resonance techniques. From PL measurements, we analyze the electron structure of the defect, and suggest it be the neutral Mo (4d2) residing on a Si site, the luminescence coming from the transition between the 3A2 multiplet of the first excited electronic configuration and the ground state 3A2.
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| 4. |
- Gällström, Andreas, 1978-, et al.
(författare)
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The Electronic Structure of the UD-4 defect in 4H, 6H and 15R SiC
- 2009
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Ingår i: Materials Science Forum, Vols. 600-603. - : Trans Tech Publications. ; , s. 397-400
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Konferensbidrag (refereegranskat)abstract
- The photoluminescence (PL) of the UD-4 defect is observed in semi-insulating bulk 4H, 6H and 15R SiC. In 4H and 6H SiC the UD-4 defect consists of two families of no-phonon (NP) lines, Ua and Ub, and in 15R SiC it consists of three families, Ua, Ub and U15R. The Ua family in 4H, 6H and 15R all show similar temperature behavior with higher energy NP lines becomming observable at higher temperatures. In the case of the Ub and U15R families, a luminescence line with lower energy than the prominent luminescence line appears at higher temperatures. The polarization and Zeeman measurements suggest that the defect has C3v symmetry.
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| 5. |
- Hahn, S., et al.
(författare)
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Contact-Less Electrical Defect Characterization of Semi-Insulating 6H-SiC Bulk Material
- 2009
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Ingår i: Materials Science Forum Vols. 600-603. - : Trans Tech Publications. ; , s. 405-408
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Konferensbidrag (refereegranskat)abstract
- The novel technique microwave detected photo induced current transient spectroscopy (MD-PICTS) was applied to semi-insulating 6H-SiC in order to investigate the properties of inherent defect levels. Defect spectra can be obtained in the similar way to conventional PICTS and DLTS. However, there is no need for contacting the samples, which allows for non-destructive and spatially resolved electrical characterization. This work is focused on the investigation of semi-insulating 6H-SiC grown under different C/Si-ratios. In the corresponding MD-PICTS spectra several shallow defect levels appear in the low temperature range. However the peak assignment needs further investigation. Additionally different trap reemission dynamics are obtained for higher temperatures, which are supposed to be due to different compensation effects.
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| 6. |
- Hsiao, C.L., et al.
(författare)
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High-phase-purity zinc-blende InN on r -plane sapphire substrate with controlled nitridation pretreatment
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:11
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Tidskriftsartikel (refereegranskat)abstract
- High-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r -plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors. © 2008 American Institute of Physics.
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| 7. |
- Janzén, Erik, 1954-, et al.
(författare)
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The Silicon vacancy in SiC
- 2009
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Konferensbidrag (refereegranskat)abstract
- A model is presented for the silicon vacancy in SiC. The previously reported photoluminescence spectra in 4H and 6H SiC attributed to the silicon vacancy are in this model due to internal transitions in the negative charge state of the silicon vacancy. The magnetic resonance signals observed are due to the initial and final states of these transitions.
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| 8. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Deep levels and carrier compensation in V-doped semi-insulating 4H-SiC
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:20
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Tidskriftsartikel (refereegranskat)abstract
- Electron paramagnetic resonance was used to study semi-insulating (SI) 4H-SiC substrates doped with vanadium (V) in the range of 5.5× 1015 -1.1× 1017 cm-3. Our results show that the electrical activation of V is low and hence only in heavily V-doped 4H-SiC, vanadium is responsible for the SI behavior, whereas in moderately V-doped substrates, the SI properties are thermally unstable and determined by intrinsic defects. We show that the commonly observed thermal activation energy Ea ∼1.1 eV in V-doped 4H-SiC may be related to deep levels of the carbon vacancy. © 2007 American Institute of Physics.
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| 9. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Deep Levels Responsible for Semi-insulating Behaviour in Vanadium-doped 4H-SiC Substrates
- 2009
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Ingår i: Materials Science Forum, Vols. 600-603. - : Trans Tech Publications. ; , s. 401-404
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Konferensbidrag (refereegranskat)abstract
- Semi-insulating (SI) 4H-SiC substrates doped with vanadium (V) in the range 5.5×1015 –1.1×1017 cm–3 were studied by electron paramagnetic resonance. We show that only in heavily V-doped 4H-SiC vanadium is responsible for the SI behavior, whereas in moderate V-doped substrates with the V concentration comparable or slightly higher than that of the shallow N donor or B acceptor, the SI properties are thermally unstable and determined by intrinsic defects. The results show that the commonly observed thermal activation energy Ea~1.1 eV in V-doped 4H-SiC, which was previously assigned to the single acceptor V4+/3+ level, may be related to deep levels of the carbon vacancy. Carrier compensation processes involving deep levels of V and intrinsic defects are discussed and possible thermal activation energies are suggested.
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| 10. |
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