Comparison of electrical defects in Ge+ and Si+ preamorphized BF2-implanted silicon

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Abstract
Silicon diode structures have been amorphized with 200‐keV Ge+ prior to BF2 implantation. Room temperature C‐V profiling revealed large concentrations of excess donor levels following epitaxial regrowth at temperatures below 800 °C. This donor formation and the annealing behavior is the same as previously observed in Si+ preamorphized substrates. Deep‐level transient spectroscopy further confirmed the similarity in the nature and spatial distribution of the defects produced. The conclusion drawn is that the same fundamental damage‐related defects are produced in the tail of the amorphizing implant in both cases. Large leakage current densities in the Ge+‐amorphized diodes were attributed to the deep‐level donors, and removal of these centers by annealing at 800 °C reduced the leakage current to ∼4×10−6 A/cm2. This current was assumed to arise from the crystallographic defects at the original amorphous/crystalline boundary which, at the ion implantation energies used, were within the zero‐bias space‐charge layer.