Effect of Ge-Incorporation on the Thermal Stability of Ge_xSb_yTe_z Phase Change Alloys for Neuromorphic Devices with Automotive Applications

Phase change chalcogenide materials, are good candidates for neuromorphic hardware intended to be embedded in microprocessors for the automotive industry, where devices must be able to operate reliably at high temperatures (&gt; 160 °C) for at least ten years. Alloys like Ge₂Sb₂Te₅ (GST225) are already a standard to realize memory devices. However, one of the major disadvantages of GST225 single layers is the low crystallization temperature (T_c), which results in low thermal stability and limited data retention. An interesting option to increase T_c is to grow Ge-rich GST alloys. Here, several Ge_xSb₂Te₅ and Ge_xSb₂Te₃ layers were grown by RF-sputtering and their thermal stability was studied by X-ray diffraction (XRD) and Raman spectroscopy as a function of temperature. The compositional analysis was performed by X-ray Fluorescence (XRF). The results showed that the T_camount grows linearly with the Ge content in the alloys; the amount of Ge segregation upon crystallization was also studied.<br/>This project has received funding from the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 824957 (“BeforeHand:” Boosting Performance of Phase Change Devices by Hetero- and Nanostructure Material Design).