Indirect electrical-control through heating of a GeTe phase change switch and Its application to reflexion type phase shifting

International audienceThis paper presents a switch based on GeTe (Germanium-Telluride) phase-change material (PCM) suitable for millimeter-wave applications. A shunt configuration with indirect excitation through heating is proposed to facilitate the implementation process in integrated circuits and to reduce impact on RF signal. Electromagnetic simulations, from 50 GHz up to 70 GHz, of two parallel switches shunted a CPW transmission line (TL) show an overall ON-state resistance (RON) of 3 Ω with an OFF-state capacitance (COFF) of 7.1 fF. This leads to a high Figure-of-Merit with a cutoff frequency of 7.5 THz. The demonstrated performance is validated through the design of a reflection-type phase shifter (RTPS), where a 3-dB branch-line coupler is loaded with tunable-length lines using those shunt-switches. Simulation results of the RTPS show great precision in terms of phase tunability with an insertion loss (IL) less than 2.7 dB at 60 GHz

Optical Actuation Performance of Phase-Change RF Switches

International audienceOptical actuation of GeTe-based radio frequency switches is studied for the first time at 915-nm optical wavelength. By inducing self-heating of the phase change material through light absorption, this approach removes the need for integrated micro-heaters. First, laser pulse conditions required to set the RF switches in ON-and OFF-states are found with optical pulse peak powers up to few hundred mW. Amorphization is obtained for optical pulses of 100 to 500 ns, and crystallization for pulses of 2 to 6 &mu;s. A resistivity ratio of 2E4 is measured between both states. Cycling endurance is performed on a 4x5 &mu;m 2 switch, overpassing 1500 cycles, which is much higher compared to previously reported optical demonstrations. Small-signal measurements show 10% lower OFF-state capacitances using optical actuation compared to electrical actuation through micro-heaters. 37 dBm power handling capability is reported in the switch OFF-state at 915 MHz. This optical actuation demonstration corresponds to a standard wavelength in integrated photonic circuits and thus, this work constitutes a first step towards a CMOS compatible fully-integrated optical actuation solution for RF switches based on phase-change material.</p