Dielectric anisotropy and phonon modes of ordered indirect-gap Al_(0.52)In_(0.48)P studied by far-infrared ellipsometry

摘要

The infrared (100-600 cm~(-1) optical properties of partially CuPt-type ordered Al_(0.52)In_(0.48)P deposited lattice matched on GaAs are studied by ellipsometry. The authors determine the ordinary and extraordinary dielectric functions and report on the evolution of the optical phonon mode frequencies of Al_(0.52)In_(0.48)P as a function of the degree of ordering. In addition to the InP- and AlP-like phonon modes, they observe two alloy-induced phonon modes which are anisotropic upon CuPt ordering. The observed modes are associated to vibrations with E and A_1 symmetries. The alloy-induced phonon modes are useful for classifying the degree of ordering in this indirect band gap alloy.