Raman spectroscopy of two novel semiconductors and related superlattices: CubicCd1−x

R. G. Alonso

¹

,

Eun‐Kyung Suh

²

,

A. K. Ramdas

³

et al.

Abstract

The Raman scattering from Cd& Zn Se and Cd& Mn"Se, grown by molecular-beam epitaxy on (001) GaAs substrates, shows zone-center optical phonons characteristic of a zinc-blende structure, indicating that these epilayers represent the cubic phase of these materials which in the bulk crystallize only in the wurtzite form. The variation of the frequency of the zone-center optical phonons as a function of composition x shows a "two-mode" behavior in Cd, "Mn Se and a pattern intermediate between "two-mode" and "one-mode" in Cd& Zn Se. The modifiedrandomelementisodisplacement model provides a satisfactory basis for these patterns. In the case of Cd& Mn Se, the large Raman shifts associated with the spin Aip of donor-bound electrons and the huge Zeeman shifts of an excitonic component observed in photoluminescence (including saturation at high magnetic fields and low temperatures), show that the large sp-d exchange interaction characteristic of diluted magnetic semiconductors is manifested also in the zinc-blende phase of this alloy.

Pressure dependence of optical phonons in ZnCdSe alloys

“…Introduction Typical first-order Raman spectra of zinc-blende-type crystals exhibit a transverse optic (TO) and a longitudinal optic (LO) zone-center phonon mode. Ternary compounds of the kind A x B 1Àx C can have a two-mode behavior with two TO and two LO modes corresponding to the binaries AC and BC (Zn x Mn 1Àx Te, Cd x Mn 1Àx Te [1], and Cd x Mn 1Àx Se [2] belong to this type of compounds), a one mode behavior (one LO and one TO mode as in Ba x Sr 1Àx F 2 and Sr x Ca 1Àx F 2 [3] with an average frequency between the modes of the parent compounds), or the so called mixed-mode behavior, where there is additionally an intermediate (I) mode between the LO and TO [1,4]. Following Vogelgesang et al [5], the multimode behavior depends on the relative masses of the constituents.…”

Long-wavelength Optical Phonons in Cd1-xMnxSe and Cd1-xFexSe Mixed Crystals

“…2 we compare our data of composition dependence of the mode energies with results calculated in [2] on the basis of Modifled Random Element Isodisplacement model [4]. A systematic shift for only local mode energies is seen.…”

“…This discrepancy could be due to the temperature differences because calculations made in [2] were based on unpublished Raman scattering data obtained at LHeT. It should be pointed out that our data give information about both: longitudinal and transverse modes, when these presented in [2] were for longitudinal modes, only. Further detailed investigations for different temperatures and with polarized light are needed to full explanation of mentioned discrepancies.…”

“…In these mixed crystals the light magnetic ion substitutes the heavy cadmium one in the wurtzite type lattice. The Raman and preliminary FIR data [2,3] show the two-mode behavior of CdMnSe crystals. The goal of the present paper is to extend the knowledge about the long-wavelength optical phonons and dielectric properties of this material.…”

Growth and properties of Zn1–x –yBex Mny Se crystals

“…The room temperature Raman spectra were measured on Zn [7] for polycrystalline α-MnSe and for ZnSe by Alonso et al [8]. In the wave number range from 104 to 272 cm -1 the transverse optical mode and longitudinal mode of MnSe are observed similar to [7], as well as the ZnSe modes.…”