Improved stability of a phase change memory device using Ge-doped SbTe at varying ambient temperature

Ge-doped SbTe (Ge–ST) was compared with Ge2Sb2Te5 (GST) for its potential use in the phase-change memory with improved stability at varying ambient temperature (TA). Device characteristics such as RESET current, RESET resistance, and SET resistance of Ge–ST devices were found to vary significantly less with TA than those of GST devices. From measured carrier density, mobility, and optical band gaps, these findings are interpreted to derive from a metallic nature of the crystalline Ge–ST in contrast with a semiconducting nature of the crystalline GST as well as a relatively weaker covalent bonding in amorphous Ge–ST.