Properties of optical phonons in Zn1−x−yMgyBexSe quaternary mixed crystal

Long wavelength optical lattice vibration and dielectric constants of the quaternary mixed crystal Zn1−x−yMgyBexSe are investigated based on the pseudo-unit-cell mode and Born–Huang procedure. It is found that this material shows a three-mode behavior and the oscillator strength of each mode is mainly controlled by only one component. The theoretical results also show that the linear interpretation method for dielectric constants is reliable. The vibrational frequencies and the oscillator strengths of the ternary mixed crystals BexZn1−xSe, BexMg1−xSe and MgxZn1−xSe are also calculated as special cases of the quaternary mixed crystal for comparing with experiments. The calculation shows agreement with the experimental results.