Photoelectric methods of potential barrier heights determination in the MOS structure

Abstract

Considerable differences between the values of Al-SiO/sub 2/-Si structure barrier heights reported in the literature may be at least partly explained by the imperfections of the measurement methods and the lack of a sufficiently accurate method of the verification of the obtained results. The most accurate, photoelectric method of contact potential difference determination is proposed in this paper to assess the accuracy of barrier height extraction. The disadvantages of the Powell method are demonstrated. It is shown that the interference phenomena have to be taken into account in the Fowler method. An improved model of the interference in a Al-SiO/sub 2/-Si structure is proposed with the interface layers, porosity, and surface oxidation of the aluminium layer taken into account. A simple, direct method of barrier height determination is proposed, too. The best agreement between the barrier heights determined by the photoelectric method and other methods was reached in the case of the Fowler method. A dependence of the Si-to-SiO/sub 2/ photoemission barrier height on the thickness of the aluminium gate has been observed, while no such dependence has been observed in the case of Al-to-Si photoemission.