GeTe薄膜电性能优化及射频应用

Optimization of electrical properties and radio frequency applications of GeTe thin film

GeTe属于硫系相变材料中的一种,利用热致相变特性可以动态实现低电阻率的晶态与高电阻率的非晶态之间可逆切换,是忆阻器和非易失射频开关领域的重要功能材料.本文以面向射频开关应用为出发点,重点对磁控溅射制备的GeTe薄膜进行电性能优化研究.通过综合分析衬底材料、溅射条件以及退火条件等因素对晶态GeTe薄膜电阻率的影响,探索出低电阻率GeTe薄膜的有效制备条件.结果表明,制备的GeTe薄膜最低晶态电阻率达到3.6×10^(-6)Ω·m,电阻比大于10~6.此外,基于规则的方形薄膜切片,构建了一款零静态功耗并联型毫米波开关,在1—40 GHz频带内,插损小于2.4 dB,隔离度大于19 dB,展示了GeTe薄膜在宽带高性能分立式非易失射频开关领域的应用潜力.

GeTe belongs to a chalcogenide phase change material,which can dynamically achieve reversible switching between the crystalline state of low resistivity and the amorphous state of high resistivity by utilizing the thermally induced phase change characteristics.The GeTe is an important functional material in the fields of memristors and nonvolatile radio frequency(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.Fig.(a) shows that compared with the GeTe film on a SiO_(2) substrate,the film on an Al_2O_(3) substrate can obtain higher crystallinity and lower resistivity.For the deposition power and pressure shown in Fig.(b),the combination of medium power(50-80 W) 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 reaches3.6×10~(-6) Ω·m,and the resistance ratio is more than 106.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.