The Electronic Contribution to the Elastic Properties of Germanium

Abstract

Theories of several elastic effects resulting from the contribution of electrons to the strain energy function of germanium are presented. They show that the elastic properties are appreciably changed by doping with donor and acceptor impurities. The properties considered are: (1) volume, (2) elastic constants of degenerate n-type material, (3) third-order elastic constants of degenerate n-type material, (4) elastic constants of degenerate p-type material, (5) elastic constants of material containing electrons bound to donors, (6) elastic constants of material containing electrons bound to pairs of donor atoms. The most striking effect is found for the case of degenerate n-type germanium, in which the theory predicts that c44 can be lowered by 8% with attainable doping levels.