RF Power-Handling Performance for Direct Actuation of Germanium Telluride Switches

The study presented in this article concerns germanium telluride (GeTe) phase-change material-based switches, actuated via direct heating and arranged through two configurations: series or shunt. It is concluded that direct heating provides a performing solution for GeTe amorphization, preventing heater aging. The two configurations are compared in terms of RF performance, power handling, and linearity. Some design rules are derived from empirical data, consolidated with thermal simulations. In either configuration, a large, thick, and short GeTe switch geometry is preferable. Higher isolation can be obtained in shunt configuration, while lower insertion loss can be reached in a series configuration. The Figure-of-Merit, as cutoff frequency, is 11 and 21 THz for shunt and series configurations, respectively. In terms of power handling, for amorphous GeTe, results confirm the existence of a threshold voltage leading to better handling for longer switches in both configurations. For crystalline GeTe, design rules that link the maximum current through the switch before failure to the material geometry are derived for the very first time. It is shown that current is proportional to the GeTe switch width, to the square root of its thickness, and inversely proportional to its length. The shunt configuration presented here holds 31 dBm at ON-state and more than 35 dBm at OFF-state while the series configuration holds 27 dBm at ON-state and 32 dBm at OFF-state. For power handling, a balance exists between series and shunt configurations with a ratio of 4 in the crystalline phase and of 0.25 in the amorphous phase.