Demonstration of a High-Speed Multi-Level Cell Phase-Change Memory Using Ge-doped SbTe

We demonstrate a high-speed multi-level cell (MLC) operation of a phase change memory with a Ge-doped SbTe (Ge-ST) for the first time using a conventional pore-type device structure as well as a conventional programming method. The Ge-ST was selected to have a low Sb/Te ratio of 1.6 (Ge-ST L ) rendering a diminished growth speed and a nucleation time relative to the case of a high Sb/Te ratio typical of fast growth-dominated crystallization. With a writing time of less than 100 ns, each of the 4 resistance levels separated from one another at least by the factor of 4 is shown to form reliably and stay with a low drift coefficient ranging 0.067 - 0.1. Ge-ST L may thus be regarded as a promising material for high-speed MLC phase change memory applications.