Directly heated four-terminal phase change switches

Measured results of a four-terminal directly heated RF phase change switch are presented. Germanium telluride (GeTe) is used as the main resistance change element, connecting the RF input/output lines. The resistivity of GeTe is switched between the high-resistance amorphous-state value of several kΩ and low-resistance crystallized value of less than 3.9 Ω in less than 404 μsec using current pulses passing though GeTe. The loss of this ohmic switch at ON state is less than 0.5 dB with isolation of more than 18 dB at frequencies up to 20 GHz, indicating a cutoff frequency of > 4 THz. The switch active area is less than 5 μm × 20 μm with GeTe volume of only 1.5 μm × 15 μm × 0.25 μm. The results presented in this paper prove phase change switches are competitive contenders as low-loss and fast RF power switches.