Development of cap-free sputtered GeTe films for inline phase change switch based RF circuits

Germanium telluride (GeTe) films have been recently demonstrated as the active element in low-loss RF switches where a 7.3 THz cut-off frequency (F-co) was achieved. In order to simultaneously realize the low ON-state transmission loss and large OFF-state isolation required for this application, significant optimization of the GeTe films was required. In particular, minimizing contact resistance (R-c) and sheet resistivity (R-sheet) without the use of a capping layer is a necessity. Varying the GeTe deposition conditions led to a wide range of structural, chemical, and electrical properties, which ultimately enabled the demonstration of a capless GeTe inline phase change switch (IPCS) structure. Conversely, improper deposition conditions led to extensive oxidation which would push R-c and R-sheet to unacceptable levels. In addition to its relevance for IPCS devices, this work has implications for the environmental stability of GeTe as a function of its physical morphology. (c) 2014 American Vacuum Society.