Local-mode frequencies due to isoelectronic impurities in zinc-blende-type crystals

The localized mode frequencies for a number of isoelectronic impurity atoms in II-VI and III-V compounds have been calculated in the mass-defect approximation by the Green's-function method. The results of a seven-parameter second-neighbor-ionic (SNI) model for the host lattice have been employed for computing the high-frequency lattice Green's function. The calculated local-mode frequencies are seen to be in strikingly good agreement with the experimental values. Thus the isoelectronic impurities in zinc-blende-type crystals discussed in the present article behave very nearly as mass defects.