Fano Factor in Germanium at 77°K

The Fano factor in germanium at liquid-nitrogen temperature has been found to be $F=0.129\mathrm{}\pm 0.003$ using $\gamma$ rays at energies from 0.122 to 4.8 MeV. $F$ appears to be independent of the primary energy in the investigated energy range. Care has been exercised to eliminate the influence of ballistic deficit, recombination, and trapping in planar lithium-drifted structures as well as noise, drift, and pile-up in the apparatus. Measurements with crystals having volumes from 0.8 to 13 cm gave consistent results. We examined the line shift and the linewidth dependence up to and into electric field strengths where saturation of electron and hole velocities occurs.