Process-induced and gold acceptor defects in silicon.

Abstract

We report detailed measurements of the thermal properties of two different defects in silicon: the gold impurity and the process-induced defects generated by rapid thermal annealing. It is found that the ratio of the concentration of the gold acceptor to the gold donor is about 5, but both levels are completely hydrogen passivated, in contrast to other results reported in the literature. We have also measured the hole-capture cross section of the gold donor in n-type silicon and found a value of 1.8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}14}$ ${\mathrm{cm}}^{2}$ which is larger than that reported in p-type silicon. The second part of this work deals with the gold acceptor and the process-induced centers. We show that their electron thermal-emission rates are identical and field independent, at least up to ${10}^{5}$ V/cm. Like the gold acceptor, the process-induced defect controls the thermally generated carriers in the depletion region. In contrast to the gold acceptor, we show that the total entropy of creation of e-h pairs, via the process-induced level, is very close to the entropy of the silicon band gap. The hole-capture cross section at the negatively charged gold-acceptor level decreases with the electric field which makes its temperature dependence weaker. However, the Coulombic potential does not properly fit the experimental results. Finally, it is reported that oxygen plays a crucial role in the stability of the process-induced defects generated by rapid thermal annealing. Our results support the hypothesis that the process-induced defect is probably the basis of the gold acceptor and perhaps other midgap levels, as already reported.