Germanium content dependence of the leakage current of recessed SiGe source/drain junctions

Abstract

The impact of the Ge fraction (x), on the leakage current of recessed Si_1−x Ge _x p⁺-n source/drain junctions has been investigated, for a fixed recess depth of 70 nm. It is found that both the bulk and the peripheral leakage current density increase approximately exponentially with increasing Ge content in the range 10–30%. Roughly speaking, the leakage current density increases one decade for every 5% increase in Ge. In case of the bulk leakage current density, this enhancement is shown to be related to the increase in extended defects penetrating the depletion region in the n-type silicon substrate. Transmission Electron Microscopy demonstrates a higher density of dislocations at the epitaxial interface for a higher Ge fraction, which are most likely generated by strain relaxation, induced by the implantation and activation of B in the p⁺ S/D regions.