ELECTRONIC-PROPERTIES OF IDEAL AND INTERFACE-MODIFIED METAL-SEMICONDUCTOR INTERFACES

The electronic properties of metal-semiconductor or Schottky contacts are characterized by their barrier heights. At ideal contacts, they ar e determined by the continuum of metal-induced gap states. Extrinsic i nterface defects and dipoles as well as interlayers may be present in real contacts and will modify the barrier heights. The zero-charge-tra nsfer barrier height and a slope parameter describe the chemical trend s of the barrier heights of Schottky contacts on a specific semiconduc tor. The zero-charge-transfer barrier heights may be calculated by usi ng the empirical tight-binding method with universal parameters and th e width of the dielectric band gaps and the slope parameters are given by the optical dielectric constants of the semiconductors. This is ve rified by comparison with numerical data from well-established theoret ical approaches. Hydrogen doping of metal-diamond and metal-silicon in terfaces changes their barrier heights with opposite sign. This is exp lained by a different orientation of H-C and H-Si interface dipoles. A g and Pb/Si(111) contacts may be prepared with a ''7x7'' and a 1x1 int erface structure. The difference of their barrier heights is explained by the electric dipole correlated with the stacking fault which is a characteristic of 7x7 reconstructions. Interlayers will also alter the barrier heights of Schottky contacts. Typical examples are SiO2 and S i3N4, i.e., MOS and MNS structures. Previous investigations found thei r barrier heights to vary as a function of the metals used. The chemic al trends of these two data sets are described by the slope parameters predicted from the optical dielectric constants of SiO2 and Si3N4. (C ) 1996 American Vacuum Society.