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): ${{\sigma }_h}^{-}\simeq 1\times {10}^{-13\mathrm{}}$ ${\mathrm{cm}}^2$, ${{\sigma }_e}^0\simeq 6\times {10}^{-14\mathrm{}}$ ${\mathrm{cm}}^2$, ${{\sigma }_e}^{-}\simeq {10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$. 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×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ 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 $k=0\mathrm{}$.

• Received 18 September 1959

DOI:https://doi.org/10.1103/PhysRev.117.1191