GeTe belongs to a chalcogenide phase change material, which can dynamically achieve reversible switching between low resistivity crystalline state and the high resistivity amorphous state of by utilizing the thermally induced phase change characteristics. The GeTe is an important functional material in the fields of memristors and nonvolatile RF switches. For RF switch applications, this paper focuses on optimizing the electrical performance of GeTe thin films prepared by magnetron sputtering. By comprehensively analyzing the effects of substrate materials, sputtering conditions, and annealing conditions on the resistivity of crystalline GeTe films, effective conditions for preparing low resistivity GeTe films are explored. Figure (a) shows that compared with the GeTe film on a SiO<sub>2</sub> substrate, the film on an Al<sub>2</sub>O<sub>3</sub> substrate can obtain high crystallinity and low resistivity. For the deposition power and pressure shown in Fig. (b), the combination of medium power (50–80W) and low pressure (2–3 mTorr) is beneficial for low crystalline resistivity of GeTe film. Additionally, Fig. (c) shows that higher annealing temperature (350–400 ℃) can realize lower film resistivity. Finally, the experimental results show that the lowest crystalline resistivity of the prepared GeTe thin film reaches 3.6×10<sup>–6</sup> Ω·m, and the resistance ratio is more than 10<sup>6</sup>. Based on rectangular chips of GeTe film, a parallel millimeter-wave switch with zero static power is also constructed. As shown in Fig. (d), the insertion loss is less than 2.4 dB, and the isolation is greater than 19 dB in a 1–40 GHz frequency band, demonstrating the potential application of GeTe thin films in the field of broadband high-performance discrete nonvolatile RF switches.
