Effect of Pressure on the Energy Levels of Impurities in Semiconductors. III. Gold in Germanium

Abstract

Gold can exist in substitutional positions in germanium in four states of ionization, with which are associated four energy levels in the forbidden energy gap. Appropriate doping and counterdoping with group V and group III elements allow each level to ionize independently of the others in certain temperature ranges. The separation in energy of the level from the band edges can thus be found. The pressure dependence of these separations can also be determined from the effect of the resultant change in carrier density on the resistivity. The measurements were carried out up to 6000 kg ${\mathrm{cm}}^{-2\mathrm{}}$ between 45 and 273°K. Equations for analyzing the multi-energy level systems are developed and calculations indicating how these equations can be used in actual situations are included in a set of appendices. Corrections for the effects of changes in mobility and density-of-states on the resistivity are also considered. The results indicate that the pressure coefficients of all four levels are much greater than for the hydrogenic impurities, and that the separation from the conduction band increases much more rapidly than that from the valence band.