Effective metal screening and Schottky-barrier formation in metal-GaAs structures

The Fermi-level movement in a Schottky barrier is investigated using a bimetal thin-film structure. The functional dependence of the barrier height on the inner metal thickness is formulated in terms of the metal effective screening length and the interface trap states. This model is used to describe experimental results on Pt-Ti-GaAs and Ti-Pt-GaAs diodes. It is found that the effective screening lengths for Pt and Ti are 6.5 and 7.0 AA, respectively, significantly greater than the ideal values of the theory of N.F. Mott and H. Jones (1958). This indicates that the potential drop inside the metal electrode can evolve over several monolayers in a Schottky contact. >