RAMAN-SPECTRA OF ZN1-XMGXSYSE1-Y QUATERNARY ALLOYS

Semiconductor quaternary alloys Zn1-xMgxSySe1-y were grown on GaAs sub strates by molecular beam epitaxy. The crystal structures were determi ned from x-ray diffraction spectra. The Raman spectra of both perpendi cular and parallel polarization geometries were measured. The followin g long-wavelength optical-phonon modes were identified: ZnSe-like TO a nd LO modes, and MgSe-like and ZnMgS-like LO modes, For the alloys wit h the same Mg composition x, the vibration frequencies of ZnSe-like TO and LO modes were observed to change linearly with S composition y fo r y <0.5. The vibration frequency of the MgSe-like LO mode was also ob served to change linearly with y for 0.1<y(0.5. (C) 1996 American Inst itute of Physics.