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The physical mechanisms that regulate carrier transport in polycrystalline chalcogenides, such as Ge2Sb2Te5 (GST), are still debated. Recently, self-induced Joule-heating (SJH) effect has been claimed to be the key factor in explaining the nonlinearity of the I-V characteristics of polycrystalline GST-based phase-change memory (PCM). In this paper, we carefully investigate the SJH occurring in the GST material by analyzing the I-V characteristics of PCM cells at low voltages, i.e., in the memory-cell readout region. To accomplish the study, we use ad hoc fabricated PCM devices allowing an easier evaluation of SJH occurring in the chalcogenide layer. A novel procedure to test the SJH effect is also proposed. A comparison between numerical simulations and compact modeling is discussed as well. Our paper shows that the SJH effect is not sufficient to reproduce the experimental I-V nonlinearity, claiming for new experiments and theoretical investigations. Therefore, this paper can be considered a step forward toward the comprehension of the transport properties of polycrystalline GST, which is a key aspect for robust modeling of PCM devices.