The in-plane dispersion of the hole subband (HSB) in a Si quantum well is obtained for the first time by applying angle-resolved photoemission spectroscopy and surface science techniques. The entire shape of the HSB over a wide ranged wave vector, including admixing of heavy and light hole subbands around the crossing point and the camelback structure inducing negative effective mass, is visualized directly. Energy separations between the subbands are quantitatively explained.

We investigated the effect of surface carrier concentration on the quantum levels and the in-plane effective masses of the subbands in Si͑111͒ p-type inversion layers. Two inversion layers with different surface carrier concentrations were made as a result of metallic surface structures. The subband dispersion was measured by angle-resolved photoelectron spectroscopy. The energy levels of the observed subbands at k = 0.0 Å −1 partially agree with the results of the calculation using the triangular approximation. The effective masses are not significantly affected by the surface carrier concentration. The spatial extension of the subband wave functions is discussed.

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