HYDROGEN-MODIFICATION OF ELECTRONIC SURFACE, BULK, AND INTERFACE PROPERTIES OF SILICON

Silicon surfaces may be covered with hydrogen by adsorption of atomic hydrogen and by wet chemical etching. The adsorption of hydrogen induc es additional surface dipoles and new surface states. The occupied H-i nduced surface states are below the valence-band maximum so that the b ands should be flat up to the surface. However. after H-termination by wet chemical etching the Fermi level is pinned close to midgap positi on for n- and p-type bulk doping. This behavior is not caused by any k ind of defect states but was explained by a passivation of shallow imp urities due to an incorporation of hydrogen from the etching solution. Capacitance-voltage characteristics of lead contacts on H-terminated silicon samples demonstrate a penetration of hydrogen up to 1 mu m bel ow the interface. In comparison to what is observed with clean interfa ces hydrogen-doping reduces the barrier heights of metal-p-diamond con tacts but increases it at Pb-p-silicon interfaces. Hydrogen induced in terface dipoles explain this behavior. They are oppositely oriented at diamond and silicon interfaces since hydrogen is more electronegative than silicon but electropositive compared to carbon.