Schottky-barrier behavior of a Ti-W alloy on Si(100)

Abstract

The Schottky-barrier height of a Ti-W alloy of 23 at.% Ti concentration, on both n-type and p-type Si(100), has been measured in the temperature range 170-295 K using current-voltage technique. Auger electron spectroscopy/depth- composition profiling, Rutherford backscattering spectroscopy, and glancing-angle x-ray diffraction were used to monitor the reaction between the alloy and Si. The results showed that the interdiffusion of Ti and Si dominates the interfacial reaction in this alloy-Si (100) system. Further, Ti rather than W dominated the barrier height. The n- and p-type barrier heights for both the metal and the silicide phase were found to decrease with increasing temperature with the sum equal, within the experimental error, to the Si indirect energy gap at any measured temperature. These results indicate that the change in barrier heights with temperature are mainly due to the temperature dependence of the indirect energy gap in Si. Further, the temperature coefficients of the n- and p-type barrier heights were found to be the same within the experimental error, and they were approximately equal to one-half the temperature coefficient of the Si indirect gap, consistent with the predictions of a recent model of barrier formation based on Fermi-level pinning in the center of the indirect gap.