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[en] In this thesis, the electrical transport properties of crystalline phase change materials are discussed. Phase change materials (PCM) are a special class of semiconducting and metallic thin film alloys, typically with a high amount of the group five element antimony or the group six element tellurium, such as Ge2Sb2Te5. The unique property portfolio of this material class makes it suitable for memory applications. PCMs reveal fast switching between two stable room-temperature phases (amorphous and crystalline) realized by optical laser or electrical current pulses in memory devices. Additionally, a pronounced property contrast in form of optical reflectivity and electrical conductivity between the amorphous and crystalline phase is the characteristic fingerprint of PCMs. The emerging electrical solid state memory PCRAM is a very promising candidate to replace Flash memory in the near future or to even become a universal memory, which is non-volatile and shows the speed and cyclability of DRAM. One of the main technological challenges is the switching process into the amorphous state, which is the most power demanding step. In order to reduce the switching power, the crystalline resistivity needs to be increased at a given voltage. Thus understanding and tayloring of this property is mandatory. In this work, first the technological relevance, i.e. optical and electrical memory concepts based on PCMs are introduced. Subsequently a description of the physical properties of PCMs in four categories is given. Namely, structure, kinetics, optical properties and electrical properties are discussed. Then important recent developments such as the identification of resonant bonding in crystalline PCMs and a property predicting coordination scheme are briefly reviewed. The following chapter deals with the theoretical background of electrical transport, while the next chapter introduces the experimental techniques: Sputtering, XRR, XRD, DSC, thermal annealing, profilometry, ellipsometry, FTIR spectroscopy, van der Pauw,Hall, and phase change optical and electrical switching techniques which are used to obtain the results. The latter chapter is split into two parts. In the first one thematerial class of doped Sb2Te is investigated with respect to structural, kinetic, optical and electrical properties. The second part covers the study of the systematic variation of the resistivity of pseudo-binary GeTe-Sb2Te3 alloys upon thermal annealing. This variation is discussed in the framework of an insulator to metal transition with the help of results from a combined van der Pauw, XRD, Hall, STM and FTIR study.