Optical properties of gold acceptor and donor levels in silicon

Abstract

The absolute values of all four photoionization cross sections for electron and hole emission from the gold acceptor and donor levels in silicon have been evaluated by measuring junction photocurrents. By using two light sources it has been shown that steady-state photocurrents provide a unique determination of threshold energies for transitions between the energy bands and the impurity levels, independent of the type of junction. Not too far away from the threshold energies, the experimental results are in good agreement with the δ-function impurity potential model of Lucovsky. Threshold energies of 0.555 and 0.61 eV are obtained for the electron and hole emission from the acceptor levels, respectively, and 0.75–0.83 and 0.345 eV for the corresponding emissions from the donor levels. For the acceptor levels, the sum of the threshold energies (1.165 eV) is very close to the band gap (1.166 eV), which indicates that relaxation effects are small. In addition, the influence of the valence-band structure on the energy dependence of the photoionization cross section for the hole emission has been investigated.