THEORETICAL INTERPRETATION OF SCHOTTKY BARRIERS AND OHMIC CONTACTS
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We review a theory of Schottky barriers that explains the following experimental findings: (i) observed barrier heights and Fermi-level pinning positions for GaAs, InP, GaSb, AlAs, GaP, InAs, and other III-V semiconductors; (ii) switching of the observed barrier heights and Fermi-level pinning positions for III-V semiconductors as a function of surface treatment or reactivity of the metal; (iii) alloy dependence of Schottky barrier heights for the ternaries Al1-xGaxAs, GaAs1-xPx, Ga1-xInxP, InP1-xAsx, and In1-xGaxAs; (iv) different slopes dE/dx for different metal contacts to AlGaAs, and an apparent cusp in the slope for Al contacts as a function of alloy composition; (v) observed Schottky barriers for a wide variety of Si/transition-metal-silicide interfaces; (vi) observed barriers for Ge, diamond, and amorphous Si; (vii) observation that Fermi-level pinning for p-GaAs disappears at the annealing temperature of the antisite defect AsGa. The theory provides a microscopic realization of the phenomenological defect model of Spicer, Lindau and coworkers. We find that most Schottky barriers are explained by dangling bonds - intrinsic dangling bonds for group IV semiconductors and antisite (as well as intrinsic) dangling bonds for III-V semiconductors. Ohmic contacts are explained in the present picture by shallow levels, which are also predicted by the theory. 1986.
