PRESSURE-DEPENDENCE OF THE FANO ASYMMETRY OF OPTICAL PHONONS IN ZN1-XCOXSE AND ZN1-XFEXSE

Effects of hydrostatic pressure on the optical phonons in ZnSe doped w ith Co and Fe at 10 K and up to 5 GPa are presented. Raman spectra fro m Zn1-xCoxSe (x = 1.6%) show the LO phonon developing an asymmetry wit h increasing pressure while the asymmetry already present at 1 bar in the x = 7.4% sample increases slightly with pressure. The optical phon on in Zn1-xFexSe (x = 8.8%) shows no modifications to its line profile for all pressures. These results are discussed in terms of a coupling between the phonons and a Raman continuum that is thought to arise th rough a pressure tunable pd hybridization of the low lying crystal fie ld levels and the valence band.