On the photoinduced phase transition in (GeTe)n(Sb2Te3)m

TL;DR

This paper presents a phenomenological model explaining how photo-excitation and high temperatures induce phase transitions in Ge-Sb-Te alloys, highlighting the role of inverse population and Coulomb interactions in the process.

Contribution

It introduces a new phenomenological explanation for photoinduced phase transitions in Ge-Sb-Te alloys, emphasizing the combined effect of light and temperature on atomic configurations.

Findings

Photo-excitation and high temperature are both necessary for phase transition.

Inverse population of nucleons stabilizes the crystalline phase.

Ge ions are pushed into interstitial positions to reduce Coulomb energy.

Abstract

We suggest a phenomenological description of the photo-conversion in Ge-Sb-Te phase-change memory alloys from amorphous to crystalline phase which explains why both photo-excitation and high temperatures T > 160C are required for the transition from hexagonal to tetrahedral phase. The position of chemical potential at high temperatures allows light induced inverse population of the nucleons of the crystalline phase which are not stable otherwise. Then, inverse population accumulates holes on neighboring Te and Ge ions and locks the photo-conversion transition by pushing Ge ions into the interstitial position to minimize the Coulomb repulsion energy.