Minority-Carrier Mobility in p -Type Germanium Under High Uniaxial Stress

The minority-carrier drift mobility in a single crystal of germanium containing 3×{}10¹⁵ indium atoms per cc has been measured as a function of uniaxial compression in a lattice $〈111〉$ direction at room temperature by observing directly the drift of an excess carrier concentration under the influence of an applied electric field. The maximum fractional change in length of the crystal, cut in the shape of a rod, was 0.99%, corresponding to a compressive pressure of approximately 1.5×{}10¹⁰ dyn cm^-2, sufficiently high to transfer substantially all conduction electrons to a single valley. A comparison of the experimental data with theoretical estimates of mobility variation due to strain-induced population transfer in the conduction band yielded a value for the scattering anistropy of κ_τ=3.7±0.3. This value is considerably higher than that obtained from studies of magnetoresistance of n-type germanium, the difference in the results being attributed to electron-hole scattering in the excess-carrier-drift mobility measurements.