Thermal evolution of the band edges of 6H-SiC: X-ray methods compared to the optical band gap

• Published in: Journal of electron spectroscopy and related phenomena Vol. 197; pp. 37 - 42
• Main Authors: Miedema, P.S., Beye, M., Könnecke, R., Schiwietz, G., Föhlisch, A.
• Format: Journal Article
• Language: English; French; German
• Published: Elsevier B.V 01.12.2014
• Subjects: Asymmetry; Band spectra; Evolution; Inelastic scattering; RIXS; Semiconductors; Silicon; Silicon carbide; Slopes; X-rays; XAS; XES; Silicon carbide; XAS; RIXS; Semiconductors; XES
• ISSN: 0368-2048; 1873-2526
• DOI: 10.1016/j.elspec.2014.08.003

•Conduction band minima (CBM) of 6H-SiC are estimated with Si 2p XAS.•Valence band maxima (VBM) of 6H-SiC are estimated with non-resonant Si 2p XES.•Temperature-dependent VBM and CBM of 6H-SiC show asymmetric band gap closing.•XAS, XES and RIXS band gap estimates are compared with the optical band gap.•XAS+XES versus optical band gap provides core-excitonic screening energies. The band gap of semiconductors like silicon and silicon carbide (SiC) is the key for their device properties. In this research, the band gap of 6H-SiC and its temperature dependence were analyzed with silicon 2p X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) allowing for a separate analysis of the conduction-band minimum (CBM) and valence-band maximum (VBM) components of the band gap. The temperature-dependent asymmetric band gap shrinking of 6H-SiC was determined with a valence-band slope of +2.45×10−4eV/K and a conduction-band slope of −1.334×10−4eV/K. The apparent asymmetry, e.g., that two thirds of the band-gap shrinking with increasing temperature is due to the VBM evolution in 6H-SiC, is similar to the asymmetry obtained for pure silicon before. The overall band gap temperature-dependence determined with XAS and non-resonant XES is compared to temperature-dependent optical studies. The core-excitonic binding energy appearing in the Si 2p XAS is extracted as the main difference. In addition, the energy loss of the onset of the first band in RIXS yields to values similar to the optical band gap over the tested temperature range.