BINDING ENTHALPIES AND ENTROPIES OF NEUTRAL ZN, IN AND SN IN GE

A statistical thermodynamical model is developed for a doubly ionizable acceptor with excited states in an elemental semiconductor. The special cases of a singly ionizable acceptor, no excited acceptor states and a neutral solute are readily extracted. The equations obtained describe not only the distribution of an acceptor among its various electronic states but also the chemical potentials of the acceptor atom and of the solvent atom. The equations are applied, with and without the excited states included, to obtain about equally good fits to the low-temperature, low carrier concentration Hall data for Zn in Ge. For the low impurity concentrations involved, the excited states are present and so should be included in the analysis. The ability to obtain an equally good fit with the excited states omitted is most likely due to the fact that the concentrations of the major Zn impurity and the Sb counter dopant are not fixed independently of the Hall measurements.