The reflectivity, luminescence, and resonant LO-phonon Raman scattering (RRS) of nominally undoped ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Zn}}_{\mathrm{x}}$Te (x∼0.5) have been studied in the spectral range near the band gap and at low temperatures. Using the reflectivity spectrum and the Zeeman splitting of selectively excited luminescence, the range of intrinsic 1S excitons is identified. The LO-phonon RRS is strongly enhanced for excitation into the 1S band and in the energy range ħ${\omega }_{\mathrm{LO}}$ above it. The outgoing beam resonance is twice as strong as the incoming beam resonance. For CdTe and ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Zn}}_{\mathrm{x}}$Te with x≤0.3, the two resonances have equal intensity. Therefore, alloy disorder is taken as the origin of the asymmetry between these two resonances. A model is presented that assumes that the LO-phonon RRS profile is determined by the scattering of the extended 1S excitons by random potential fluctuations. Using perturbation expansion of the excitonic wave functions, it is shown that a good fit to the experimental RRS profile is obtained by admixing exciton states with ‖K‖≤0.07π/a (a is the lattice constant) and a constant potential amplitude of 0.05 eV.

• Received 30 May 1989

DOI:https://doi.org/10.1103/PhysRevB.40.8313