IR ellipsometry and photoluminescence investigations of Zn_(1-x)Be_xSe and Zn_(1-x-y)Be_xMn_ySe mixed crystals

摘要

Optical properties related to lattice vibrations and photoluminecence of Zn_(1-x)Be_xSe and Zn_(1-x-y)Be_xMn_ySe alloys are presented. Optical phonons of the mixed crystals grown in a sphalerite phase for composition 0≤x≤0.35 and 0≤y≤0.22 have been investigated by IR spectroscopic ellipsometry in the wave number range 230-8000 cm~(-1). The complex dielectric functions can be reproduced using a model with three classical damped oscillators corresponding to the BeSe-like modes and a Drude contribution from the free carriers. The zone-centre optical-phonon frequencies increase continuously with increasing Be concentration. The amplitudes of the vibrations are also increasing with Be content.