The adsorption of 1/3 monolayer of the group-III elements B, Al, Ga, and In on a Si-terminated SiC(111)-(√3 x √3)R30° surface was investigated in dependence on the surface preparation conditions using the density functional theory. The energetics, the bonding behaviour and the resulting surface electronic structure were studied and chemical trends were derived. For the metal atoms Al, Ga, and In the replacement of a Si atom in a T4 position always gives the most stable configuration. The first-row element B showed a completely different behaviour. Under Si-rich conditions boron replaces a second-layer C atom in a S5 position, whereas under C-rich conditions a first-layer Si atom was replaced by boron. The different adsorbate configurations result in completely different surface electronic structures. Al, Ga, and In adsorption passivated the surface. The fundamental gap was virtually free from empty or occupied surface states. The B adsorption in the S5 configuration follows this behaviour. However, boron substituting a Si-atom gives rise to an empty mid-gap surface band.

Stability, Reconstruction, and Surface Electronic States of Group-III Atoms on SiC(111). U.Grossner, J.Furthmüller, F.Bechstedt: Physical Review B, 2001, 64[16], 165308 (7pp)