Low-Temperature Specific Heat of Germanium

Electronic and lattice contributions to the specific heat are reported for several $n$-type degenerate Ge ignots. The electronic effective mass, calculated on the assumption of a parabolic conduction band, is not strongly dependent on donor concentration in Ge. The Debye temperature decreases as donor or acceptor impurities are added, from 371°K for pure Ge to 362°K for the most heavily doped ingot. However, this marked decrease did not occur in silicon-doped Ge. It is suggested that the effect is due to screening of long-range lattice forces by free electrons or holes.