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

Lead contacts were prepared by evaporation on H-terminated Si(111) sur faces at room temperature. The Si(111):H-1 X 1 surfaces were obtained by wet chemical etching in buffered hydrofluoric acid. For p-type-dope d substrates the zero-bias barrier heights, which were determined from current-voltage characteristics measured with these contacts, were fo und to decrease with increasing ideality factor. This plot gives a zer o-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 contact s on n-type doped substrates reveal quasi-ohmic behaviour with a resis tance 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 inter face, which decreases or increases the barrier height of n- or p-type- doped samples, respectively.