Multi-level cell storage with a modulated current method for phase-change memory using Ge-doped SbTe

Abstract

We demonstrate a high-speed multi-level cell (MLC) storage for the phase-change memory using a Ge-doped SbTe (GeST) for the first time with a conventional pore-type device structure and a conventional modulated-current writing method. The GeST was selected to have a low Sb-to-Te ratio of 1.8 (GeST L), rendering a diminished growth rate relative to the case of a high Sb-to-Te ratio typically 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 of ∼0.1. GeST L may be regarded as a promising material for high-speed MLC phase-change memory application.