Raman spectra of ZnGeAs2 highly doped with Mn

We have studied optical, electrical and structural properties of the semimagnetic semiconducting ZnGeAs2 crystals, undoped and doped with 1.5, 3 and 3.5 wt% Mn, which is perspective material for spintronics. We used Raman spectroscopy as a sensitive method for precise determination of crystal structure. In addition to the vibrational frequencies of a ZnGeAs2 lattice, MnAs clusters and Mn complexes, which we have already experimentally registered at similar materials, the existence of As clusters in this material is revealed for the first time. Based on the obtained results we concluded that arsenic clusters of various sizes exist, including form of molecules – As4. We assume that they are located in the vicinity of the grain boundaries and that the distribution of free carriers in the samples was inhomogeneous.