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| 2. |
- ul-Hassan, Jawad, et al.
(författare)
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Control of epitaxial graphene thickness on 4H-SiC(0001) and bufferlayer removal through hydrogen intercalation
- 2012
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Ingår i: Materials Science Forum (Volumes 717 - 720). - : Trans Tech Publications Inc.. ; , s. 605-608
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Konferensbidrag (refereegranskat)abstract
- We report graphene thickness, uniformity and surface morphology dependence on thegrowth temperature and local variations in the off-cut of Si-face 4H-SiC on-axis substrates. Thetransformation of the buffer layer through hydrogen intercalation and the subsequent influence onthe charge carrier mobility are also studied. A hot-wall CVD reactor was used for in-situ etching,graphene growth in vacuum and the hydrogen intercalation process. The number of graphene layersis found to be dependent on the growth temperature while the surface morphology also depends onthe local off-cut of the substrate and results in a non-homogeneous surface. Additionally, the influence of dislocations on surface morphology and graphene thickness uniformity is also presented.
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| 3. |
- Engelbrecht, J.A. A., et al.
(författare)
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Impact of dielectric parameters on the reflectivity of 3C-SiC wafers with a rough surface morphology in the reststrahlen region
- 2014
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Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 439, s. 115-118
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Tidskriftsartikel (refereegranskat)abstract
- A layer-on-substrate model is used to obtain the infrared reflectance for 3C-SiC with a rough surface morphology. The effect of varying dielectric parameters of the "damaged layer" on the observed reflectivity of the 3C-SiC in the reststrahlen region is assessed. Different simulated reflectance spectra are obtained to those if the dielectric parameters of the "substrate" were varied. Most notable changes in the shape of the simulated reststrahlen peak are observed for changes in the high frequency dielectric constant, the phonon damping constant, the phonon frequencies and "thickness" of damaged surface layer.
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| 4. |
- Engelbrecht, J. A. A., et al.
(författare)
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Notes on the plasma resonance peak employed to determine doping in SiC
- 2015
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Ingår i: Infrared physics & technology. - : ELSEVIER SCIENCE BV. - 1350-4495 .- 1879-0275. ; 72, s. 95-100
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Tidskriftsartikel (refereegranskat)abstract
- The doping level of a semiconductor material can be determined using the plasma resonance frequency to obtain the carrier concentration associated with doping. This paper provides an overview of the procedure for the three most common polytypes of SiC. Results for 3C-SiC are presented and discussed. In phosphorus doped samples analysed, it is submitted that the 2nd plasma resonance cannot be detected due to high values of the free carrier damping constant gamma. (C) 2015 Elsevier B.V. All rights reserved.
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| 5. |
- Engelbrecht, J A A, et al.
(författare)
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The origin of a peak in the reststrahlen region of SiC
- 2012
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Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 407:10, s. 1525-1528
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Tidskriftsartikel (refereegranskat)abstract
- A peak in the reststrahlen region of SiC is analyzed in order to establish the origin of this peak. The peak can be associated with a thin damaged layer on the SiC wafers, and a relation is found between surface roughness and the height of this peak, by modeling the damaged layer as an additional layer when simulating the reflectivity from the wafers.
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| 6. |
- Fagerlind, Martin, 1980, et al.
(författare)
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Influence of Large-Aspect-Ratio Surface Roughness on Electrical Characteristics of AlGaN/AlN/GaN HFETs
- 2012
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Ingår i: IEEE Transactions on Device and Materials Reliability. - : Institute of Electrical and Electronics Engineers (IEEE). - 1530-4388 .- 1558-2574. ; 12:3, s. 538-546
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Tidskriftsartikel (refereegranskat)abstract
- The effect of large-aspect-ratio surface roughness of AlGaN/GaN wafers is investigated. The roughness has a surface morphology consisting of hexagonal peaks with maximum peak-to-valley height of more than 100 nm and lateral peak-to-peak distance between 25 and 100 mu m. Two epitaxial wafers grown at the same time on SiC substrates having different surface orientation and with a resulting difference in AlGaN surface roughness are investigated. Almost no difference is seen in the electrical characteristics of the materials, and the electrical uniformity of the rough material is comparable to that of the smoother material. The reliability of heterostructure field-effect transistors from both materials have been tested by stressing devices for up to 100 h without any significant degradation. No critical effect, from the surface roughness, on device fabrication is experienced, with the exception that the roughness will directly interfere with step-height measurements.
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| 7. |
- Galindo-Uribarri, A., et al.
(författare)
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Superdeformation below [Formula Presented]
- 1996
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Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 54:2, s. 454-458
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Tidskriftsartikel (refereegranskat)abstract
- A decoupled rotational band with an average dynamical moment of inertia [Formula Presented] [Formula Presented]/MeV has been observed to high spin in [Formula Presented] [Formula Presented]. The measured quadrupole moment of [Formula Presented] eb is as large as that of the superdeformed band in [Formula Presented]. The large deformation and decoupled character of the band suggests that the odd neutron occupies either the [Formula Presented] orbital or the [Formula Presented] intruder orbital. This is the first example of a superdeformed band extending to high spin below [Formula Presented], a neutron number that has long been considered as the boundary for superdeformation in the [Formula Presented] mass region.
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