Bulk Lattice Instability in II-VI Semiconductors and Its Effect on Impurity Compensation

From the results of first-principles pseudopotential calculations we identify a new type of low energy lattice instability that is most effective in acceptor passivation in II-VI semiconductors. The instability occurs in the presence of free holes and involves the breaking of two host bonds and the creation of a VI-VI dimer bond. The model provides a satisfactory explanation for persistent photoconductivity, its optical threshold, and for the observation of a deep “donor” level in photoluminescence measurements on $p$-doped samples.