Improving the performance of Ge$_2$Sb$_2$Te$_5$ materials via nickel doping: Towards RF-compatible phase-change devices

TL;DR

This study demonstrates that nickel doping in Ge2Sb2Te5 significantly reduces resistivity contrast between amorphous and crystalline states, enhancing electrical switching performance without affecting optical or structural properties, enabling RF-compatible phase-change devices.

Contribution

Introduces a nickel doping method that improves electrical switching in GST materials while maintaining optical and structural integrity, advancing phase-change device technology.

Findings

Resistivity contrast reduced by nearly three orders of magnitude.

Optical properties remain unchanged after doping.

Lattice structure and thermal transport are unaffected.

Abstract

High-speed electrical switching of Ge2Sb2Te5 (GST) remains a challenging task due to the large impedance mismatch between the low-conductivity amorphous state and the high-conductivity crystalline state. In this letter, we demonstrate an effective doping scheme using nickel to reduce the resistivity contrast between the amorphous and crystalline states by nearly three orders of magnitude. Most importantly, our results show that doping produces the desired electrical performance without adversely affecting the film's optical properties. The nickel doping level is approximately 2% and the lattice structure remains nearly unchanged when compared with undoped-GST. The refractive indices at amorphous and crystalline states were obtained using ellipsometry which echoes the results from XRD. The material's thermal transport properties are measured using time-domain thermoreflectance (TDTR), showing no change upon doping. The advantages of this doping system will open up new opportunities for designing electrically reconfigurable high speed optical elements in the near-infrared spectrum.