HighStress Piezoresistance and Mobility in Degenerate SbDoped Germanium
Abstract
The resistivity of germanium containing between N=3×10^{17} and 10^{19} antimony atoms per cc was measured at 1.2°K under uniaxial compressions of up to 10^{10} dyn cm^{2}. These stresses are high enough to effect an observable saturation in the piezoresistance, that is, to transfer all electrons to a single conductionband valley ([111] compression) or to two valleys ([110] compression). Two distinct ranges are observed in degenerate germanium: for N<10^{18} cm^{3} the mobility increases with N and shows impurityband effects; for N>10^{18} cm^{3} the mobility decreases and ionizedimpurity scattering is the dominant scattering process. The latter range is N>3×10^{18} cm^{3} for large [111] compression. The resistivity was measured for current flowing parallel and perpendicular to the stress direction. The mobility anisotropy was found to be μ_{⊥}μ_{II}=3.9+/0.1 for N>4×10^{18} cm^{3}. This indicates that the mean free path is nearly isotropic. The mobility for electrons in 1, 2, and 4 valleys is compared with Csavinszky's partialwave treatment of impurity scattering. The change of screening with the number of valleys was taken into account. Csavinszky's theory overestimates the N dependence and the magnitude of the scattering. This is attributed to the failure of the individualscattering assumption.
 Publication:

Physical Review
 Pub Date:
 March 1965
 DOI:
 10.1103/PhysRev.137.A1847
 Bibcode:
 1965PhRv..137.1847C