INTERFACIAL REACTIONS AND SCHOTTKY BARRIERS OF PT AND PD ON EPITAXIAL SI1-XGEX ALLOYS

The evolution of interfacial reactions during the deposition of Pt and Pd on epitaxial Si1-xGex alloys was studied using x-ray photoelectron spectroscopy (XPS) for metal coverage up to 10 angstrom. Auger electron depth profiling was performed on a thicker metal overlayer before and after in vacuo annealing to study the redistribution of composition in the reactions. We have found that Pt and Pd react mainly with Si to form silicides at 350-degrees-C, leaving some Ge to segregate at the surface. These results were correlated with Schottky barrier height measurements. We found that the Schottky barrier heights of Pt/n-Si0.8Ge0.2 and Pd/n-Si0.8Ge0.2 are about the same, pinned at 0.68 eV, which is much smaller than those of n-Si. These barrier heights are quite stable up to 550-degrees-C.