LEAD CONTACTS ON SI(111) - H-1 X-1 SURFACES

Lead contacts were prepared by evaporation on H-terminated Si(111) surfaces at room temperature. The Si(111):H-1 X 1 surfaces were obtained by wet chemical etching in buffered hydrofluoric acid. For p-type-doped substrates the zero-bias barrier heights, which were determined from current-voltage characteristics measured with these contacts, were found to decrease with increasing ideality factor. This plot gives a zero-bias barrier height of 0.71 eV for an ideality factor of 1.01 which is obtained for image force-lowering of the barrier only. Lead contacts on n-type doped substrates reveal quasi-ohmic behaviour with a resistance of 79 Omega. On the contrary, lead contacts on p- and n-type Si(111)-7 X 7 surfaces are known to have ohmic and rectifying properties, respectively. The results can be explained by an additional hydrogen-induced charge of positive sign on the semiconductor side of the interface, which decreases or increases the barrier height of n- or p-type-doped samples, respectively.