Recombination-Generation and Optical Properties of Gold Acceptor in Silicon

Abstract

The thermal emission rates of electrons and holes at the gold acceptor center ${E}_{C}\ensuremath{-}{E}_{\mathrm{Au}\ensuremath{-}}=540$ meV) in silicon are obtained from 200 to 300\ifmmode^\circ\else\textdegree\fi{}K in silicon using the photovoltaic effect in the depletion region of a reverse biased $p\ensuremath{-}n$ junction. The observed electric field dependences are considerably smaller than that predicted by the three-dimensional Poole-Frenkel effect in a Coulombic potential, but closer to that in a polarization potential. The ratio $\frac{{{e}_{n}}^{t}}{{{e}_{p}}^{t}}$ is 50 at 190\ifmmode^\circ\else\textdegree\fi{}K and decreases to 16 at 300\ifmmode^\circ\else\textdegree\fi{}K. The low field values of the thermal emission rates, ${{e}_{n}}^{t}$ and ${{e}_{p}}^{t}$, are used to compute the thermal-capture cross sections of electrons and holes which show ${{\ensuremath{\sigma}}_{n}}^{t}\ensuremath{\propto}{T}^{0}$ and ${{\ensuremath{\sigma}}_{p}}^{t}\ensuremath{\propto}{T}^{\ensuremath{-}4}$ and are consistent with Lax's impurity model. The degeneracy factors obtained from these emission-rate data and the capture-cross-section data of Fairfield and Gokhale are 15 and 7.5 for the electron and hole transitions, which are not inconsistent with those of the one-band model. The photoionization cross sections of electrons and holes and their spectral dependences are also obtained from -56 to -78\ifmmode^\circ\else\textdegree\fi{}C and compared with the $\ensuremath{\delta}$-function impurity potential model of Lucovsky, giving an effective-field ratio of ${(\frac{m}{{m}^{*}})}^{\frac{1}{2}}(\frac{{\ensuremath{\epsilon}}_{\mathrm{eff}}}{{\ensuremath{\epsilon}}_{0}})\ensuremath{\sim}3\ensuremath{-}4$ for holes and \ensuremath{\sim}1.3 for electrons. No temperature and field dependences are observed. Radiative recombination cross sections obtained from detailed balance are 6.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ ${\mathrm{cm}}^{2}$ for holes and 3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ ${\mathrm{cm}}^{2}$ for electrons at 300\ifmmode^\circ\else\textdegree\fi{}K.