Infrared Properties of Gold in Germanium

The fundamental parameters of gold in germanium have been investigated between 60-300^∘{}K by absorption, photoconductivity, and lifetime studies.Photoconductivity measurements reveal the following capture cross sections for electrons and holes at 80^∘{}K (subscript refers to carrier being captured; superscript to charge state of gold center): σₕ^-1×10^-13 cm², σₑ⁰6×10^-14 cm², σₑ^-10^-17 cm². Lifetime studies on n-type samples show the existence of a 0.018-ev Coulomb barrier at singly charged sites and an indication that a thermal (phonon) mechanism is involved in the electron capture process. The lifetime also manifests itself in the noise spectrum.The photoconductive absorption cross section at 80^∘{}K of p-type gold-doped germanium (0.15-ev level) is found to be 2×{}10^-16 cm² at 1.8 microns. It is suggested that differences between the absorption and photoconductive spectra are due to departure from spherical symmetry of valence band contours away from $k=0$.