Recombination-Generation and Optical Properties of Gold Acceptor in Silicon

Abstract

The thermal emission rates of electrons and holes at the gold acceptor center $E_C-E_{\mathrm{Au}-}=540\mathrm{}$ meV) in silicon are obtained from 200 to 300°K in silicon using the photovoltaic effect in the depletion region of a reverse biased $p-n$ 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°K and decreases to 16 at 300°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 ${{\sigma }_n}^t\propto T^0$ and ${{\sigma }_p}^t\propto T^{-4\mathrm{}}$ 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°C and compared with the $\delta$-function impurity potential model of Lucovsky, giving an effective-field ratio of ${\left(\frac{m}{m^{*}}\right)}^{\frac{1}{2}}\left(\frac{{\epsilon }_{\mathrm{eff}}}{{\epsilon }_0}\right)\sim 3-4$ for holes and ∼1.3 for electrons. No temperature and field dependences are observed. Radiative recombination cross sections obtained from detailed balance are 6.3×${10}^{-21\mathrm{}}$ ${\mathrm{cm}}^2$ for holes and 3×${10}^{-21\mathrm{}}$ ${\mathrm{cm}}^2$ for electrons at 300°K.