Dielectric functions of bulk 4H and 6H SiC and spectroscopic ellipsometry studies of thin SiC films on Si

Abstract

Articles you may be interested inVisible to vacuum ultraviolet dielectric functions of epitaxial graphene on 3C and 4H SiC polytypes determined by spectroscopic ellipsometry Details of below band-gap uniaxial dielectric function of SiC polytypes studied by spectroscopic ellipsometry and polarized light transmission spectroscopy Spectroscopic rotating-analyzer ellipsometry employing a compensator and optical transmission were used to measure the dielectric functions of bulk 4H and 6H SiC from 0.72 to 6.6 eV for light propagating nearly parallel to the hexagonal axis. The measurements below the band gap show the presence of a thin surface layer, which was modeled as SiO 2 . The data are similar to results for cubic ͑3C͒ and 6H SiC from the literature, but differences are notable, particularly above 4 eV. At 5.56 eV, we observe a critical point in 4H SiC, which is assigned to direct interband transitions along the UϭM ϪL axis in the hexagonal Brillouin zone after comparison with band structure calculations. No evidence for direct transitions below 6.5 eV was found in 6H SiC. We apply our results to the analysis of a 4H SiC film on insulator ͑SiCOI͒ produced by high-dose hydrogen implantation and direct wafer bonding on Si. For comparison, we also studied a 1 m thick epitaxial layer of 3C SiC on Si, where the interference oscillations are influenced by surface and interface roughness.

Morphological and electronic properties of epitaxial graphene on SiC

“…Experimental  and  spectra, obtained from bare 4H-, 6H-and and 3C SiC substrates, were measured and analyzed employing a sum of broadened harmonic oscillator lineshapes. The obtained model dielectric function (MDF) spectra are equivalent to those reported previously for the respective polytypes [16][17][18], but are omitted here for brevity. The best-match substrate MDF parameters were then used in the analysis of the epitaxial graphene samples but were not further varied.…”

A diffraction-based technique for determination of interband absorption coefficients in bulk 3C-, 4H- and 6H-SiC crystals

“…The lower limit for absorption coefficent is obtained from αd < 8 condition, at which the α min = 8/d~200 cm -1 can be determined for 400 µm thick sample. The calculations have shown that the proposed method allows determination of high absorption coefficient using very thick wafers (αd > 8), when its value can not be determined by transmission measurements or ellipsometric techniques [15]. On the other hand, lower absorption coefficient (αd < 8) can be extracted either by the proposed method or by conventional UV-VIS spectrometry [15], as well by scanning the carrier density in-depth profile [17].…”

“…here ω=2π/λ 1 is the probe frequency, Γ ω is the frequency of the effective bandgap (direct, E Γ =7.3 eV for 4H-and 6H-SiC [15]), n eh is the refractive index change by one electron-hole pair, * eh m is the reduced electron-hole effective mass, and n 1 is the refractive index for probe wavelength. , and as well on a parameter ( )…”

“…The calculations have shown that the proposed method allows determination of high absorption coefficient using very thick wafers (αd > 8), when its value can not be determined by transmission measurements or ellipsometric techniques [15]. On the other hand, lower absorption coefficient (αd < 8) can be extracted either by the proposed method or by conventional UV-VIS spectrometry [15], as well by scanning the carrier density in-depth profile [17]. The proposed method allows determination of the temperature-dependent absorption coefficient, fitted by the approximations, given in section 2.4.…”

“…according to [15], here E Γ = 7.3 eV is the energy of the effective direct gap. Refractive index of 3C has very similar value and spectral dependence [22].…”