Interpretation of Fermi level pinning on 4H-SiC using synchrotron photoemission spectroscopy

The Fermi level movements on 4H-SiC were observed in in situ deposited Ni contact using synchrotron radiation photoemission spectroscopy. For n-type SiC, the surface band bending increased about 0.75 eV with the Ni deposition, meaning the shift of Fermi level towards valence band edge. The barrier height was calculated to be 1.61 eV, consistent with the Schottky–Mott theory (1.65 eV). For p-type SiC, however, the barrier height was 0.95 eV, lower than theoretical value (1.61 eV). The large discrepancy is due to the defect level (activation energy=0.96 eV) observed by deep level transient spectroscopy, leading to a major role in pinning the Fermi level in p-type SiC.