Germanium telluride (GeTe) is a phase change material (PCM) that undergoes an exponential decrease in resistance from room temperature to its transition temperature at approximately 200 °C. Its resistivity decreases by as much as six orders of magnitude between amorphous and crystalline phases as it is heated. Chalcogenides such as GeTe have been utilized typically in nonvolatile optical memories such as CDs, DVDs, and Blu-ray discs, where the change in reflectivity between phases gives enough contrast for ON and OFF bits. Research over the past several years has begun to characterize the electronic control of PCM thin films for advanced electronic memory applications. By applying a voltage to control its resistance and crystallinity, GeTe has become a candidate for ultra-fast switching electronic memory, perhaps as an alternative to Flash memory. In this research, micro-scale PCM cells were fabricated using RF sputtering of a GeTe target and electron-beam evaporation on c-Si, SiO₂/Si, Si₃N₄/Si, and Al₂O₃. Characterizations of the crystallization process were completed with spectroscopic ellipsometry (SE), varied voltage, and varied temperature in order to draw a comparison of the switching mechanism between thermally and electronically induced transition. The results show an optical contrast of ∆n + i∆k = -0.858 + i1.056. Heat conduction experiments prove a growthdominated crystallization and fracturing of conductive crystallites when deposited on Al₂O₃. PCM cells exhibit memory-like I-V curves for smaller cell dimensions according to the trap-limited conduction model in chalcogenides. RF structures show the capability of being utilized as improved RF switches.

Date Published: 13 March 2015
PDF: 10 pages
Proc. SPIE 9364, Oxide-based Materials and Devices VI, 93640G (13 March 2015); doi: 10.1117/12.2079359

Published in SPIE Proceedings Vol. 9364:
Oxide-based Materials and Devices VI
Ferechteh H. Teherani; David C. Look; David J. Rogers, Editor(s)