In this dissertation, we investigated ZnSe-based materials, which are interesting for a variety of potential applications in various devices. There was only limited information available in the literature about Zn1-xMnxSe material parameters like the electron effective mass and transport properties. In this work, we explored many new details about this interesting material using Fourier transform infrared spectroscopy and some other experimental techniques. The fundamental aspects related to lattice vibrations in mixed crystal alloys and reststrahlen band were also studied. In summary the following results have been obtained in this thesis: (A) Results from the series of chlorine-doped Zn1-xMnxSe samples: To extract information about the electron effective mass we performed roomtemperature plasma edge measurements on chlorine-doped n-type Zn1-xMnxSe epilayers. Via Drude-Lorentz-type multi-oscillator fits to our data, we extracted the optical electron effective mass (m*) in chlorine doped Zn1-xMnxSe:Cl samples for different Mn contents and free-electron concentrations. The free-electron concentration was determined using room-temperature van-der-Pauw Hall effect measurements. Our results indicate that: (A1) The electron effective mass in Zn1-xMnxSe is lower than that for ZnSe. A distinct reduction of the electron effective mass is observed upon Mn incorporation.