Threshold-Voltage Modulated Phase Change Heterojunction

Phase change random access memory(PCRAM) is one of the most important candidates for the next generation non-volatile memory technology. However, the ability to reduce its memory size is compromised by the fundamental limitations inherent in the CMOS technology. While 0T1 R configuration without any additional access transistor shows great advantages in improving the storage density, the leakage current and small operation window limit its application in large-scale arrays. Phase change heterojunction based on p-type phase change materials and n-type semiconductor are proposed to provide solutions for the current problem in PCRAM. It doesn't need any access transistor, realized the integration of selector and storage cell, and provide a large operate window which could enhance the operation stability.In this work, phase change heterojunction based on GeTe and n-Si is fabricated to address those problems. Phase change heterojunction with self-rectification realized the integration of selector and storage cell. The relationship between threshold voltage and doping concentration is investigated and energy band diagrams and XPS measurements are provided to explain the results. The threshold voltage is modulated to provide a large operational window based on this relationship. The switching performance of the heterojunction is also tested, showing a good reverse characteristic, which could effectively decrease the leakage current. Furthermore, a reliable read-write-erase function is achieved during the tests. Phase change heterojunction is proposed for high-density memory, showing some notable advantages, such as modulated threshold voltage, large operational window and low leakage current. Thus, phase change heterojunction is proposed for high-density memory, especially phase change memory.