Influence of physisorbed water on the conductivity of hydrogen terminated silicon-on-insulator surfaces

The sheet resistance of hydrogen terminated silicon-on-insulator substrates increases significantly with time in air due to depletion of free carriers, attributed to the growth of electrically active defects as the surface oxidizes. Surprisingly, physisorbed water (via adsorption from ambient or controlled exposure in vacuum) causes an increase in the conductivity. This effect is largely reversible when the water layer is displaced by inert gas purging, heating, or pumping. The observed conductivity changes are correlated with Hall voltage changes, indicating that the adsorbed water layer induces accumulation of majority carriers on n-doped substrates. (c) 2007 American Institute of Physics.