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We have investigated the ͑ ͱ 3 ϫ ͱ 3͒R30°reconstructed 4H-SiC͑0001͒ surface using k ជ -resolved inverse photoemission. Undergoing a Mott-Hubbard transition a formerly half-filled surface band splits into a completely occupied and a completely unoccupied band. We observe a sharp peak at an energy of 1.10 eV above the Fermi level. By mapping the dispersion E͑k ជ ͒ of this surface state we show that it remains above the Fermi level throughout the whole surface Brillouin zone, thus confirming the semiconducting character of the surface. As expected for a strongly correlated system the dispersion is flat with a determined bandwidth of W = ͑0.26± 0.10͒ eV. Including recent ARUPS measurements we are able to deduce a Mott-Hubbard parameter of U = ͑2.2± 0.2͒ eV. These results are in accordance with experiments performed on the 6H-SiC͑0001͒ surface, which shows a slightly different electronic structure. We therefore confirm that the Mott-Hubbard splitting for the ͑ ͱ 3 ϫ ͱ 3͒R30°reconstructed surface is independent of the underlying polytype as predicted by theory.

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