Defects in Cd1−xMnxGeAs2 lattice

Abstract

CdGeAs2 is a promising material for optical applications. It has the wide transparency range between 2.3 and 18 μm except harmful absorption region at 5.5 μm. Its presence is related to the crystal lattice quality. The measurements of Raman and far infrared reflectivity spectra of the series of Cd1−xMnxGeAs2 samples (0 ≤ x ≤ 0.037) were carried out in spectral range from 60 to 400 cm−1, at room temperature. Beside all expected optical modes three defect modes are registered at about 125, 170 and 235 cm−1. Their intensities are related to tetragonal distortion of lattice (Δ) so we connected them with lattice defects GeAs, usually formed in this material, and CdAs2 and Cd3As2 clusters whose characteristic frequencies match these values. Antisite defects GeAs are connected to energy level at about 200 meV and to absorption at 5.5 μm. Based on obtained results we can conclude that doping with small amount of manganese (x = 0.004) results in slight deformation of CdGeAs2 crystal lattice and consequently considerably reducing the formation of antisite defects GeAs.