Aug 16, 2019

Optical Transmission, Photoluminescence, and Raman Scattering of Porous SiC Prepared from p-Type 6H SiC

The optical transmission, temperature-dependence of the photoluminescence (PL), and Raman scattering of porous SiC prepared from p-type 6H-SiC are compared with those from bulk p-type 6H-SiC. While the transmission spectrum of bulk SiC at room temperature reveals a relatively sharp edge corresponding to its band gap at 3.03 eV, the transmission edge of porous SiC (PSC) is too wide to determine its band gap. It is believed that this wide edge might be due to surface states in PSC. At room temperature, the PL from PSC is 20 times stronger than that from bulk SiC. The PL PSC spectrum is essentially independent of temperature. The relative intensities of the Raman scattering peaks from PSC are largely independent of the polarization configuration, in contrast to those from bulk SiC, which suggests that the local order is fairly random.





Source:IOPscience
For more information, please visit our website: www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Aug 9, 2019

The fabrication of nickel silicide ohmic contacts to n-type 6H-silicon carbide

This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi2/SiC structure are formed on N-wells created by N+ ion implantation into Si-faced p-type 6H-SiC epilayer respectively. NiSi and NiSi2 films are prepared by annealing the Ni and Si films separately deposited. A two-step annealing technology is performed for decreasing of oxidation problems occurred during high temperature processes. The specific contact resistance ρc of NiSi contact to n-type 6H-SiC as low as 1.78 × 10−6Ωcm2 is achieved after a two-step annealing at 350 °C for 20 min and 950° C for 3 min in N2. And 3.84 × 10−6Ωcm2 for NiSi2 contact is achieved. The result for sheet resistance Rsh of the N+ implanted layers is about 1210Ω/squ. X-ray diffraction analysis shows the formation of nickel silicide phases at the metal/n-SiC interface after thermal annealing. The surfaces of the nickel silicide after thermal annealing are analysed by scanning electron microscope.


Source:IOPscience
For more information, please visit our website: www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Aug 1, 2019

Origin of a fourfold symmetric (0 0 0 6) Bragg diffraction intensity in -scan mode on a 6H-SiC crystal

The quality of silicon carbide (SiC), when used as a substrate, has profound effects on the growth of the homo/hetero-epitaxial film on it. Here, a fourfold symmetric (0006) x-ray diffraction intensity in a phiv-scan mode is found to have nothing to do with the deformation of wafers or the existence of mosaic domains, regardless of whether it is a double-sided polished 6H-SiC wafer or a thick 6H-SiC slice. The experimental results show that both the diffraction intensity and its full width at half maximum as a function of the azimuth angle phiv exhibit the features of four peaks and four valleys regularly. By measuring the bending of the diffraction planes along the azimuth angles at the peaks and valleys, saddle-shaped deformed (0 0 0 1) atomic planes of the 6H-SiC in macroscopic scale are hypothesized. Based on the hypothesis, a model analysis of the diffraction intensity matched well with the observed anisotropic symmetric x-ray diffraction in a 6H-SiC single crystal.



Source:IOPscience
For more information, please visit our website: www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Jul 23, 2019

Piezoresistance consideration on n-type 6H SiC for MEMS-based piezoresistance sensors

Piezoresistance in n-type 6H SiC was analyzed on the basis of electron transfer and mobility shift mechanisms for hexagonal many-valley semiconductors. Three important gauge factors or coefficients for piezoresistive sensor application, i.e., the longitudinal, transverse and shear, were calculated by using band parameters. The calculation was compared with experimental results taken from the literature. It was shown that incorporation of the electron transfer and the mobility shift mechanisms gives reasonable interpretation for the piezoresistance in n-type 6H SiC within the temperature range from 300 K to 773 K, and impurity concentration n = 2 × 1019 to 3.3 × 1019 cm−3. These conditions correspond to typical operation ranges of state-of-the-art MEMS-based piezoresistive sensors.



Source:IOPscience
For more information, please visit our website: www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Jul 17, 2019

Surface Morphological Structures of 4H-, 6H- and 15R-SiC (0001) Epitaxial Layers Grown by Chemical Vapor Deposition

Surface structures of SiC epitaxial layers grown on 4H-, 6H- and 15R-SiC (0001) substrates have been investigated using an optical microscope and an atomic force microscope (AFM). SiC epitaxial layers of 5–15 µm thickness have been grown by chemical vapor deposition on 4H-, 6H- and 15R-SiC (0001) Si-face substrates with 0.2–8.0° off-angle. AFM observation reveals that macrostep formation with a submicron periodicity is reduced by increasing the off-angle of substrates, leading to a small surface roughness of 0.18–0.22 nm. The bunched steps with two and three Si–C bilayer heights are dominant for 4H- and 6H-SiC epitaxial layers, respectively, while 15R-SiC epitaxial layers show both two and three Si–C bilayer height steps, reflecting the peculiar stacking structure of each polytype. By optimization of the growth process, the surface defect density has been reduced from 1200–4500 cm-2 to 50–250 cm-2.



Source:IOPscience
For more information, please visit our website: www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Jul 9, 2019

Defects mediated ferromagnetism in a V-doped 6H—SiC single crystal

Undoped and V-doped 6H—SiC single crystals have been grown by the physical vapor transport method. The V concentration is determined to be 3.76 × 1017 at/cm3 and 6.14 × 1017 at/cm3 by secondary ion mass spectrometry for low V-doped and high V-doped SiC samples, respectively. The undoped 6H—SiC shows diamagnetism, while the V-doped 6H—SiC exhibits weak ferromagnetism. The lower V-doped sample shows stronger ferromagnetism compared to that of the higher V-doped sample. However, the structural characterization indicates that the lower V-doped SiC has a relative poor crystalline quality. It is found that both V dopants and defects are essential for introducing ferromagnetic exchange in V-doped SiC single crystals.



Source:IOPscience
For more information, please visit our website: www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Jul 5, 2019

The effects of displacement threshold irradiation energy on deep levels in p-type 6H-SiC

We report on the electrical characterization, by means of deep level transient spectroscopy, of electron-irradiated Al-doped 6H-SiC epilayers. Samples were irradiated with either 116 keV, in order to displace only carbon atoms, or 400 keV. Seven deep traps, in the 0.1–1.6 eV range above the valence band, were found. The thermal stability of the detected levels was analyzed by performing an isochronal annealing series in the 100–1800 °C temperature range and the atomic structure of most of the detected traps was found to be related to C-displacement.


Source:IOPscience
For more information, please visit our website: www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com