| 1. |
- Booker, Ian Don, et al.
(författare)
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Comparison of post-growth carrier lifetime improvement methods for 4H-SiC epilayers
- 2012
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Ingår i: Silicon Carbide And Related Materials 2011, Pts 1 And 2. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 285-288, s. 285-288
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Konferensbidrag (refereegranskat)abstract
- We compare two methods for post-growth improvement of bulk carrier lifetime in 4H-SiC: dry oxidations and implantations with either 12C or 14N, followed by high temperature anneals in Ar atmosphere. Application of these techniques to samples cut from the same wafer/epilayer yields 2- to 11-fold lifetime increases, with the implantation/annealing technique shown to give greater maximum lifetimes. The maximum lifetimes reached are ∼5 μs after 12C implantation at 600 °C and annealing in Ar for 180 minutes at 1500 °C. At higher annealing temperatures the lifetimes decreases, a result which differs from reports in the literature.
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| 2. |
- Gällström, Andreas, et al.
(författare)
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Electronic Configuration of Tungsten in 4H-, 6H-, and 15R-SiC
- 2012
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Ingår i: Materials Science Forum Vols 717 - 720. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 211-216
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Konferensbidrag (refereegranskat)abstract
- A commonly observed unidentified photoluminescence center in SiC is UD-1. In this report, the UD-1 center is identified to be tungsten related. The identification is based on (i) a W-doping study, the confirmation of W in the samples was made using deep level transient spectroscopy (DLTS), (ii) the optical activation energy of the absorption of UD-1 in weakly n-type samples corresponds to the activation energy of the deep tungsten center observed using DLTS. The tungsten-related optical centers are reported in 4H-, 6H-, and 15R-SiC. Further, a crystal field model for a tungsten atom occupying a Si-site is suggested. This crystal field model is in agreement with the experimental data available: polarization, temperature dependence and magnetic field splitting.
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| 3. |
- Kang, M. -S, et al.
(författare)
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Metal work-function and doping-concentration dependent barrier height of Ni-contacts to 4H-SiC with metal-embedded nano-particles
- 2012
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783037854198 ; 717-720, s. 857-860
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effect of the metal work-function and doping concentration on the barrier height of Ni-contacts with embedded nano-particles (NPs) on 4H-SiC surfaces. Both n-type epitaxial layers with N-D=1x10(16) cm(-3), and layers doped by phosphorus implantation to a doping concentration of similar to 1x10(19) cm(-3) are used. The barrier height is reduced with increasing doping concentration and the silver (Ag) nano-particles (R similar to 18.5 nm) further enhance the local electric field of the electrical contacts to 4H-SiC in comparison to gold (Au) nano-particles (R similar to 20.2 nm). In the case of ion-implanted samples, the barrier height of the fabricated SiC diode structures with embedded Ag-NPs was significantly reduced by similar to 0.09 eV and similar to 0.25 eV compared to the samples with Au-NPs and the sample without NPs, respectively.
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| 4. |
- Lanni, Luigia, et al.
(författare)
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Bipolar integrated OR-NOR gate in 4H-SiC
- 2012
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783037854198 ; 717-720, s. 1257-1260
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Tidskriftsartikel (refereegranskat)abstract
- An integrated bipolar OR-NOR gate based on emitter coupled logic (ECL) is demonstrated in 4H-SiC. Operated from 27 up to 300 °C on -15 V supply voltage the logic gate exhibits stable noise margins (NMs) of about 1 V in the entire temperature range, and high and low output voltage levels that move towards positive voltages when the temperature increases: from -3 up to -2.7 V and from -5.4 up to -5.1 V respectively. In the same temperature range transistor current gain (β) goes from 46 down to 21.
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| 5. |
- Lee, J. -H, et al.
(författare)
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Local anodic oxidation of phosphorus-implanted 4H-SiC by atomic force microscopy
- 2012
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783037854198 ; 717-720, s. 905-908
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Tidskriftsartikel (refereegranskat)abstract
- In this work, local oxidation behavior in phosphorus ion-implanted 4H-SiC has been investigated by using atomic force microscopy (AFM). The AFM-local oxidation (LO) has been performed on the implanted samples, with and without activation anneal, using varying applied bias (15/20/25 V). It has been clearly shown that the post-implantation annealing process at 1650 °C has a great impact on the local oxidation rate by electrically activating the dopants and by modulating the surface roughness. In addition, the composition of resulting oxides changes depending on the doping level of SiC surfaces.
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| 6. |
- Lim, Jang-Kwon, et al.
(författare)
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A theoretical and experimental comparison of 4H- and 6H-SiC MSM UV photodetectors
- 2012
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Ingår i: Silicon Carbide and Related Materials 2011. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 1207-1210
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Konferensbidrag (refereegranskat)abstract
- This paper reports on fabrication and modeling of 4H- and 6H-SiC metal-semiconductor-metal (MSM) photodetectors (PDs). MSM PDs have been fabricated on 4H-SiC and 6H-SiC epitaxial layers, and their performance analyzed by MEDICI simulation and measurements. The simulations were also used to optimize the sensitivity by varying the width and spacing of the interdigitated electrodes. The fabricated PDs with 2 ÎŒm wide metal electrodes and 3 ÎŒm spacing between the electrodes exhibited, under UV illumination, a peak current to dark current ratio of 10 5 and 10 4 in 4H-SiC and 6H-SiC, respectively. The measured spectral responsivity of 6H-SiC PDs was higher compared to that of 4H-SiC PDs, with a cutoff at 407 nm compared to 384 nm in 4H-SiC PDs. Also the peak responsivity occurred at a shorter wavelength in 6H material. A high rejection ratio between the photocurrent and dark current was found in both cases. These experimental results were in agreement with simulation.
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| 7. |
- Linnarsson, Margareta K., et al.
(författare)
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Mn implantation for new applications of 4H-SiC
- 2012
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Ingår i: Silicon Carbide and Related Materials 2011. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 221-224
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Konferensbidrag (refereegranskat)abstract
- Structural disorder and lattice recovery of high dose, manganese implanted, semiinsulating, 4H-SiC have been studied by secondary ion mass spectrometry, Rutherford backscattering in channeling directions, visible-to-near infrared optical spectroscopy as well as with transmission electron microscopy. After heat treatment at 1400 and 1600 °C, a substantial rearrangement of manganese is observed in the implanted region. However, the crystal has not been fully recovered. More disorder remains in the [1123] compared to the [0001] channel direction. Stacking faults, voids and 3C inclusions are observed in the implanted region. A Mn containing phase has most likely formed.
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| 8. |
- Nipoti, R., et al.
(författare)
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High dose Al + implanted and microwave annealed 4H-SiC
- 2012
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Ingår i: Silicon Carbide and Related Materials 2011. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 817-820
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Konferensbidrag (refereegranskat)abstract
- A post implantation microwave annealing technique has been used for the electrical activation of Al + implanted ions in semi-insulating 4H-SiC. The annealing temperatures have been 2000-2100°C. The implanted Al concentration has been varied from 5 × 10 19 to 8 × 10 20 cm -3. A minimum resistivity of 2 × 10 -2 Ω·cm and about 70% electrical activation of the implanted Al has been measured at room temperature for an implanted Al concentration of 8 × 10 20 cm -3 and a microwave annealing at 2100°C for 30s.
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| 9. |
- Ou, Y., et al.
(författare)
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Photoluminescence and Raman spectroscopy characterization of boron-and nitrogen-doped 6H silicon carbide
- 2012
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Ingår i: Silicon Carbide and Related Materials 2011. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 233-236
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Konferensbidrag (refereegranskat)abstract
- Nitrogen-boron doped 6H-SiC epilayers grown on low off-axis 6H-SiC substrates have been characterized by photoluminescence and Raman spectroscopy. The photoluminescence results show that a doping larger than 10 18 cm -3 is favorable to observe the luminescence and addition of nitrogen leads to an increased luminescence. A dopant concentration difference larger than 4×10 18 cm -3 is proposed to achieve intense photoluminescence. Raman spectroscopy further confirmed the doping type and concentrations for the samples. The results indicate that N-B doped SiC can serve as a good wavelength converter in white LEDs applications.
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| 10. |
- Pearce, Ruth, et al.
(författare)
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Development of FETs and resistive devices based on epitaxially grown single layer graphene on SiC for highly sensitive gas detection
- 2012
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Ingår i: Materials Science Forum Vols 717 - 720. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 687-690
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Konferensbidrag (refereegranskat)abstract
- Epitaxially grown single layer graphene on silicon carbide (SiC) resistive sensors were characterised for NO2 response at room and elevated temperatures, with an n-p type transition observed with increasing NO2 concentration for all sensors. The concentration of NO2 required to cause this transition varied for different graphene samples and is attributed to varying degrees of substrate induced Fermi-level (E-F) pinning above the Dirac point. The work function of a single layer device increased steadily with increasing NO2 concentration indicating no change in reaction mechanism for high and low concentrations despite a change in sensor response direction. Epitaxially grown graphene device preparation is challenging due to poor adhesion of the graphene layer to the substrate. A field effect transistor (FET) device is presented which does not require wire bonding to contacts on graphene.
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