| 1. |
- Engelbrecht, J. A. A., et al.
(författare)
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Comparison of experimental results with theoretical models for the temperature dependence of the band gap of AlxGa1-xN epilayers
- 2022
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Ingår i: Journal of materials science. Materials in electronics. - : SPRINGER. - 0957-4522 .- 1573-482X. ; 33, s. 22492-22498
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Tidskriftsartikel (refereegranskat)abstract
- The band gap energies AlxGa1-xN epilayers prepared on two different substrates were assessed using Fourier Transform Infrared (FTIR) reflectance spectroscopy, photoluminescence (PL) and scanning electron microscopy electron dispersive spectroscopy (SEM-EDS). The results were compared to various theoretical formulae to calculate the band gap, and deviations elucidated.
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| 2. |
- Chubarov, M., et al.
(författare)
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Boron nitride: A new photonic material
- 2014
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Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 439, s. 29-34
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Tidskriftsartikel (refereegranskat)abstract
- Rhombohedral boron nitride (r-BN) layers were grown on sapphire substrate in a hot-wall chemical vapor deposition reactor. Characterization of these layers is reported in details. X-ray diffraction (XRD) is used as a routine characterization tool to investigate the crystalline quality of the films and the identification of the phases is revealed using detailed pole figure measurements. Transmission electron microscopy reveals stacking of more than 40 atomic layers. Results from Fourier Transform InfraRed (FTIR) spectroscopy measurements are compared with XRD data showing that FTIR is not phase sensitive when various phases of sp(2)-BN are investigated. XRD measurements show a significant improvement of the crystalline quality when adding silicon to the gas mixture during the growth; this is further confirmed by cathodoluminescence which shows a decrease of the defects related luminescence intensity.
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| 3. |
- Chubarov, M., et al.
(författare)
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Characterization of Boron Nitride Thin Films
- 2013
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Konferensbidrag (refereegranskat)abstract
- Rhombohedral Boron Nitride layers were grown on sapphire substrate in a hot-wall CVD reactor. The characterization of those layers is reported and the results are discussed in correlation with the various growth parameters used.
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| 4. |
- Engelbrecht, J. A. A., et al.
(författare)
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Assesment of a model to calculate the refractive index of AlXGa1-XN epilayers using the multi-oscillator model simulation of the infrared reflectance
- 2022
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Ingår i: Physica. B, Condensed matter. - : ELSEVIER. - 0921-4526 .- 1873-2135. ; 625
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Tidskriftsartikel (refereegranskat)abstract
- A formula for the calculation of the refractive index of AlXGa1-XN in the infrared region has previously been proposed. In this paper, the validity of the proposed model is assessed against the multi-oscillator model which simulates the infrared reflectance of AlXGa1-XN epilayers. Acceptable agreement was found between the two models for wavenumbers greater than 3500 cm(-1). Additional validation for the earlier proposed formula is obtained by the calculation of epilayer thicknesses of AlXGa1-XN samples in the infrared region.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- Marx, G., et al.
(författare)
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Comments on a peak of AlxGa1-xN observed by infrared reflectance
- 2016
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Ingår i: Infrared physics & technology. - : ELSEVIER SCIENCE BV. - 1350-4495 .- 1879-0275. ; 76, s. 493-499
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Tidskriftsartikel (refereegranskat)abstract
- AlxGa1-xN epilayers, grown on c-plane oriented sapphire substrates by metal organic chemical vapour deposition (MOCVD), were evaluated using FTIR infrared reflectance spectroscopy. A peak at similar to 850 cm(-1) in the reflectance spectra, not reported before, was observed. Possible origins for this peak are considered and discussed. (C) 2016 Elsevier B.V. All rights reserved.
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| 9. |
- van Rooyen, I J, et al.
(författare)
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The effect of grain size and phosphorous-doping of polycrystalline 3C-SiC on infrared reflectance spectra
- 2012
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Ingår i: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 422:1-3, s. 103-108
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Tidskriftsartikel (refereegranskat)abstract
- The effect of P-doping and grain size of polycrystalline 3C-SiC on the infrared reflectance spectra is reported. The relationship between grain size and full width at half maximum (FWHM) suggest that the behavior of the 3C-SiC with the highest phosphorous doping level (of 1.2 x 10(19) at. cm(-3)) is different from those with lower doping levels (andlt;6.6 x 10(18) at. cm(-3)). It is also further demonstrated that the plasma resonance frequency (omega(p)) is not influenced by the grain size.
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