KGaA, Weinheim. We study the effects of nitrogen (N)-doping on the electrical memory reliability of GeSbTe phase-change materials based on GeTe prototype models. We find that the loss of secondary bonding (e.g., resonant interlayer bonding) determines the feasibility of various types of N-doping that can be easily adopted by the GeSbTe system. We give a more generalized explanation beyond compliance with the formation of local Ge3N4 motifs. The nitrogen-induced change in local order produces crystalline GeTe with shallow states near the valence band edge. These states are localized on the nearest-neighbor Ge sites, thus reducing the conductivity in the crystalline phase. This trend carries over to c-GeTe with Ge vacancy. The N-doped amorphous GeTe models exhibit enhanced degrees of band tail overlap, which pins the Fermi energy in the mid-gap and thus gives rise to even higher resistivities in the amorphous phases.
- Band overlapping
- Loss of secondary bonding
- Phase change memory materials
- Shallow states
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics