Miedema, P.S.; Beye, M.; Könnecke, R.; Schiwietz, G.; Föhlisch, A.: Thermal evolution of the band edges of 6H-SiC: X-ray methods compared to the optical band gap. Journal of Electron Spectroscopy and Related Phenomena 197 (2014), p. 37-42
10.1016/j.elspec.2014.08.003
Open Access Version
Abstract:
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 2pX-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-rayscattering (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 gapshrinking 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 shrinkingwith increasing temperature is due to the VBM evolution in 6H-SiC, is similar to the asymmetry obtainedfor 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 energyappearing in the Si 2p XAS is extracted as the main difference. In addition, the energy loss of the onset ofthe first band in RIXS yields to values similar to the optical band gap over the tested temperature range.