Study on Resistance of Crystalline GeTe Thin Films and Enhancement on Electrical Properties of Phase Change Switch

Chalcogenide phase change materials (PCMs) stand as promising contenders in the realm of radio frequency (RF) switches owing to their remarkable attributes including high switching speed, strong integration potential, and low-power consumption. This study endeavors to explore methods for reducing the resistance of germanium telluride (GeTe) film in its crystalline phase and consequently lowering the RF insertion loss (IL) in a phase change switch. The investigation revealed that oxidation in GeTe thin films induces changes in crystalline resistance. To mitigate oxidation, plasma bombardment with Ar <tex-math notation="LaTeX">^+</tex-math> was employed, demonstrating a substantial decrease in the resistance of crystalline film. The optimized GeTe-based phase change switch achieved an ideal resistance of 7 <tex-math notation="LaTeX">Ω</tex-math> for the ON-state and 1.2 M <tex-math notation="LaTeX">Ω</tex-math> for the OFF-state, respectively. The <tex-math notation="LaTeX">R_off</tex-math> / <tex-math notation="LaTeX">R_on</tex-math> ratio of the switch could reach 1.7 <tex-math notation="LaTeX">×</tex-math> 10 <tex-math notation="LaTeX">⁵</tex-math> . Furthermore, the optimized switch can handle RF power of <tex-math notation="LaTeX">$+$</tex-math> 37 dBm in the ON-state and self-actuates at 30 dBm in the OFF-state. RF measurements show that the IL is better than 0.4 dB and the isolation is better than 17 dB from 1 to 20 GHz.