Comparison Of Optical And Electric Properties Of Phase-change Memory Material

Currently, phase-change random access memory (PCRAM) due to its high reading/writing speed, non-volatility, simple processing, has became a hot research topic and was believed to be one of the most potential choices for next non-volatile memory. However, phase change materials play a key role in determining the performance of PCRAM. Among these phase change materials, chalcogenide is one of the most important and potential candidates to fabrication phase-change memory.In this thesis, SbTe, InSbTe, Ge2Sb2Te5(GST) and Si-doped GST with different proportions were prepared by electron beam evaporation technique. And then we studied the phase transition of the materials that induced by heating. The change of resistance during this evolution is also tested and discussed. The main results of this study are as follows:We prepared the films of SbTe and InSbTe and measured the temperature dependent resistance change of samples. It is found that the temperature of phase transition from amorphous to crystalline in SbTe and InSbTe is 68℃ and 72℃, respectively. XRD spectra confirmed this transition and indicated that the meta-stable face center cubic structure dominates the crystalline materials. Moreover, theirs resistance decrease drastically compared with the amorphous sample. The crystallization activation energy was also estimated by Kissinger formula, which showed that the activation energy of InSbTe is 60meV higher than that of SbTe. Therefore, the stability of InSbTe is better than that of SbTe. And phase transition temperature of GST is about 148℃, while that of different Si-doped GST is increased by 4-9℃. The corresponding crystallization energy is also increased and it is proportional to the Si content. The data retention time of GST doped by 15% Si is estimated be above 10 years, which meets the requirements of PCRAM device fabrication. Moreover, the stability as well as the reliability of materials after doping, are improved, and the power dissipation is decreased, which make Si doped GST more appropriate to fabricate PARAM than SbTe and InSbTe.