Raman scattering study of carrier-transport and phonon properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>4</mml:mn><mml:mi>H</mml:mi><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Si</mml:mi><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>crystals with graded doping

Nakashima, S.; Kitamura, Tatsuya; Mitani, Takeshi; Okumura, Hajime; Katsuno, Masakazu; Ohtani, Noboru

doi:10.1103/physrevb.76.245208

Cited by 60 publications

(28 citation statements)

References 42 publications

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“…The sides of the defect incorporate less nitrogen than other areas identified by Raman scattering at room temperature in Fig. 8b [30,31]. Therefore, the formation mechanism of this defect is probably the same with the new type of defect in 6H-SiC, except for the fact that lateral (10 " 10) face growth is supposed to be doped less nitrogen than that of C-terminated growth in 4H-SiC.…”

Section: The Formation Mechanism Of This New Type Of Defectmentioning

confidence: 91%

Characterizations and formation mechanism of a new type of defect related to nitrogen doping in SiC crystals

et al. 2014

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Here, we report a commonly occurring defect related to nitrogen doping in silicon carbide crystals grown by physical vapor transport method while its formation mechanism has remained unclear. It is often mislabeled as planar hexagonal void defect (PHVD) owing to their similar in shape and size on wafer surface. Our results indicate that this is a new type of defect and differs from PHVD with respect to their nitrogen concentrations, void shapes and the connections to micropipe. We found that the carbon-rich vapor during the crystal growth is responsible for the formation of this type of defect. A possible three-stage defect developing mechanism and measures to avoid the defects are proposed.

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Section: The Formation Mechanism Of This New Type Of Defectmentioning

confidence: 91%

Characterizations and formation mechanism of a new type of defect related to nitrogen doping in SiC crystals

et al. 2014

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“…The relationship between the LOPCpgc mode Raman peak position of the samples with different ion-modified layer and different laser power is shown in Figure 9, and the dotted lines represent the linear fit results for K1. When the laser power increases from 1 to 20 mW, the LOPCpgc mode Raman From literature it is known that for n-type 4H-SiC, the LOPC mode Raman peak shifts to larger wavenumbers and becomes broadened with increasing carrier concentration [22,27,32]. For p-type, though, the relationship between the LOPC peak and carrier concentration is significantly different.…”

Section: Lasermentioning

confidence: 99%

“…Klein and his colleagues [26] demonstrate that the polarization selection rules are valid for both coupled and uncoupled longitudinal optical (LO) phonon mode. The LOPC mode is the result of the coupling between plasmon and LO phonons that interact through macroscopic electric fields [27]. The theoretical analysis of the coupled mode in the cubic crystal had been extended to the hexagonal system [10,28,29].…”

Section: Determination Of Carrier Concentration From Raman Measurementsmentioning

confidence: 99%

“…For instance, the parameter K value of the epi sample is 7.37×10 15 cm −3 /mW, which means that for each 1 mW increase in laser power, the photogenerated carrier concentration increases by approximately 7.37×10 15 cm −3 . From literature it is known that for n-type 4H-SiC, the LOPC mode Raman peak shifts to larger wavenumbers and becomes broadened with increasing carrier concentration [22,27,32]. For p-type, though, the relationship between the LOPC peak and carrier concentration is significantly different.…”

Section: Lasermentioning

confidence: 99%

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Raman Characterization of Carrier Concentrations of Al-implanted 4H-SiC with Low Carrier Concentration by Photo-Generated Carrier Effect

Liu

Rommel

et al. 2019

Crystals

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In this work, 4H SiC samples with a multilayer structure (shallow implanted layer in a lowly doped n-type epitaxial layer grown on a highly doped thick substrate) were investigated by Raman scattering. First, Raman depth profiling was performed to identify characteristic peaks for the different layers. Then, Raman scattering was used to characterize the carrier concentration of the samples. In contrast to the conventional Raman scattering measuring method of the Longitudinal Optical Plasmon Coupled (LOPC) mode, which is only suitable to characterize carrier concentrations in the range from 2 × 1016 to 5 × 1018 cm−3, in this work, Raman scattering, which is based on exciting photons with an energy above the band gap of 4H-SiC, was used. The proposed method was evaluated and approved for different Al-implanted samples. It was found that with increasing laser power the Al-implanted layers lead to a consistent redshift of the LOPC Raman peak compared to the peak of the non-implanted layer, which might be explained by a consistent change in effective photo-generated carrier concentration. Besides, it could be demonstrated that the lower concentration limit of the conventional approach can be extended to a value of 5 × 1015 cm−3 with the approach presented here.

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“…In contrast, a manifest blue shift was observed when the focal plane moved from the interface of the substrate layer and the epitaxial layer to the surface of the sample (between −7.5/−6/−5.3 µm and 0 µm defocus distance). Many studies have shown the sensitivity of the LOPC mode on carrier concentration of the n-type 4H-SiC [26][27][28][29][30]. The heavily doped n-type substrates had relatively high carrier concentrations in the orders of 10 18 cm −3 , while the n-type epitaxial layers had rather low carrier concentrations of ≈1.0 × 10 16 cm −3 comparatively.…”

Section: Depth Profiling Of Net Doping Concentrationmentioning

confidence: 99%

Depth Profiling of Ion-Implanted 4H–SiC Using Confocal Raman Spectroscopy

Song

Liu

et al. 2020

Crystals

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For silicon carbide (SiC) processed by ion-implantation, dedicated test structure fabrication or destructive sample processing on test wafers are usually required to obtain depth profiles of electrical characteristics such as carrier concentration. In this study, a rapid and non-destructive approach for depth profiling is presented that uses confocal Raman microscopy. As an example, a 4H–SiC substrate with an epitaxial layer of several micrometers thick and top layer in nanoscale that was modified by ion-implantation was characterized. From the Raman depth profiling, longitudinal optical (LO) mode from the epitaxial layer and longitudinal optical phonon-plasmon coupled (LOPC) mode from the substrate layer can be sensitively distinguished at the interface. The position profile of the LOPC peak intensity in the depth direction was found to be effective in estimating the thickness of the epitaxial layer. For three kinds of epitaxial layer with thicknesses of 5.3 μm, 6 μm, and 7.5 μm, the average deviations of the Raman depth analysis were −1.7 μm, −1.2 μm, and −1.4 μm, respectively. Moreover, when moving the focal plane from the heavily doped sample (~1018 cm−3) to the epitaxial layer (~1016 cm−3), the LOPC peak showed a blue shift. The twice travel of the photon (excitation and collection) through the ion-implanted layer with doping concentrations higher than 1 × 1018 cm−3 led to a difference in the LOPC peak position for samples with the same epitaxial layer and substrate layer. Furthermore, the influences of the setup in terms of pinhole size and numerical aperture of objective lens on the depth profiling results were studied. Different from other research on Raman depth profiling, the 50× long working distance objective lens (50L× lens) was found more suitable than the 100× lens for the depth analysis 4H–SiC with a multi-layer structure.

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Raman scattering study of carrier-transport and phonon properties of4H−SiCcrystals with graded doping

Cited by 60 publications

References 42 publications

Characterizations and formation mechanism of a new type of defect related to nitrogen doping in SiC crystals

Characterizations and formation mechanism of a new type of defect related to nitrogen doping in SiC crystals

Raman Characterization of Carrier Concentrations of Al-implanted 4H-SiC with Low Carrier Concentration by Photo-Generated Carrier Effect

Depth Profiling of Ion-Implanted 4H–SiC Using Confocal Raman Spectroscopy

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