ZNSE(100) - THE SURFACE AND THE FORMATION OF SCHOTTKY BARRIERS WITH AL AND AU

A study of the ZnSe(100) surface and of its interfaces with Al and Au is presented. We find that the (2 X 1) reconstructed Se-rich surface i s terminated with a full monolayer of dimerized Se, whereas the C(2X2) reconstructed Zn-rich surface corresponds to a half-monolayer of nond imerized Zn atoms. These atomic configurations and corresponding surfa ce electron affinities are consistent with the requirement of dangling bond saturation and fully accounted for by the electron counting rule . For the metal/ZnSe interfaces, we find that Au forms an abrupt junct ion, whereas Al reacts and forms Al2Se3, releasing Zn in the process. The stabilized Fermi level position is 2.1 eV above the valence band m aximum for Al and 1.15 eV for Au, irrespective of doping type and in q ualitative agreement with the Schottky limit for the barrier heights. The Au/p-ZnSe Schottky barrier height can be reduced by 0.25 eV by int roducing a 2-3 ML Se interlayer between the metal and the semiconducto r.