Intrinsic electric fields in silicon

Silicon wafers varying in doping type and concentration have been probed using slow positrons. The variation of positron diffusion with doping is explained in terms of intrinsic electric fields extending from the native-oxide/Si interface into the crystalline bulk. Variation in the surface S parameter is correlated with the bulk Fermi level. Large variations between measured data from three differently doped samples of 70 nm amorphous Si overlayers created by ion irradiation are shown. The need for the inclusion of sample characteristics resulting from doping to obtain meaningful quantitative results is stressed.