OPTICAL-PROPERTIES OF MG-BASED II-VI TERNARIES AND QUATERNARIES - CD1-XMGXTE AND CD1-X-YMGXMNYTE

We have investigated the photoluminescence, Raman, and infrared spectra of Cd-1-x,MgxTe and Cd1-x-yMgxMnyTe bulk crystals with the zinc-blende structure. From the band-gap (E(g)) photo- luminescence peak we deduce E(g)=1.595 + 1.607 + 1.592y eV at 10 K. The Raman spectra of the quaternary alloys exhibit a classic three-mode behavior with MgTe-like, MnTe-like, and CdTe-like LO-TO pairs of zone-center optical phonons, in decreasing order of frequency. Their composition dependence follows the modified random-element isodisplacement model. For very small x and/or y, the infrared absorption spectra recorded with a Fourier-transform spectrometer clearly reveal the local modes of Mn2+ and Mg2+. Mn2+ exhibits one and Mg2+ three local modes corresponding to their isotopic abundances; the latter have frequencies proportional to 1/root M(Mg2+).