On the role of scattering by surface roughness in silicon inversion layers

Experimental results are presented, which strongly suggest that scattering of carriers by surface roughness may be important in the silicon inversion layer of metal-oxide-semiconductor structures. Low temperature data for p-type channels on identical orientation at high surface field show that mobility results in this region are dependent only on the mode of sample preparation and are independent of surface charges. The most reasonable explanation for these observations is offered by a scattering mechanism which is closely associated with the surface condition of the SiSiO₂ interface, namely, scattering by surface roughness. This scattering is a direct result of the fluctuating potential caused by the imperfect interface which is only a small distance from the inversion carriers. A calculation of the effect of surface roughness on surface carrier mobility is also given and found to be in satisfactory agreement with the experimental results. The application of the theory to the observed results permits an estimate to be made of the physical dimensions of the surface roughness of the Si-SiO₂ interface.