Research On Switching Characteristics Of Germanium Telluride Phase Change Thin Film

The microwave switch can control the switching of the signal and the conversion of the communication channel,has been widely used in major fields such as radar,communication and electronic countermeasures.The phase change switch has the advantages of low insertion loss,high speed and small size,and has great potential for application in a new generation of high-speed reconfigurable radio frequency modules.In this paper,phase transition switching characteristics of GeTe thin films are studied systematically from the perspective of making and improving the phase transition of GeTe-based switching.In this paper,firstly,a high-quality,high-performance GeTe thin film is prepared,and then its switching characteristics are analyzed.Finally,an indirect heating type switching device is simulated,designed and manufactured.The main conclusions are as follows:1.The preparation of high-quality and high-performance of GeTe thin films.By changing the magnetron sputtering parameters and annealing process,dense and uniform films with a 1:1 ratio of Ge and Te atoms were prepared.When the sputtering power was 50W and the pressure was 0.5Pa,the minimum resistivity of crystalline GeTe was 2.48×10^-6Ω·m,the resistance ratio of amorphous and crystalline states exceeds 10⁶,which satisfies the material requirements of phase change switches.2.Thy study on the structural characteristics of GeTe thin films before and after phase transformations.By XRD analysis,GeTe is amorphous and orthorhombic structure before and after annealing.Raman and XPS analysis show that in the crystallization process,the Ge-Te bond increased and the Te-Te bond did not change to ensure rapid phase transformation.3.The study on the thermal mutagenesis and electrical properties of GeTe thin films.The resistance of the GeTe shows three phenomena which slowly declines,dips and remains essentially unchanged as the temperature rises.In the slow-declining region,GeTe does not crystallize,amorphous GeTe remains in a high-impedance state and and the stability is perfect;the increase in carrier concentration is the main reason for the decrease in resistance,exhibits properties of semiconductors and capacitance characteristics.In the dip region,GeTe undergoes a phase change.During this period,the crystallization rate and the crystallization speed are greatly increased,the lattice starts to be ordered,and the rapid increase of the mobility is the main reason for the decrease of the resistance.When the resistance is almost constant,GeTe crystallizes completely,showing the properties of the metal and resistance characteristic.4.Using GeTe as the phase change layer,a phase change switch model was designed by HFSS and COMSOL simulation software.For the first time,using TaN as the heating layer and Ta₂O₅ obtained by oxidation as the electrical isolation layer,a complete GeTe-based indirect heating type phase change switch was designed and manufactured.The microwave testing on the fabricated device in the frequency range of0-20 GHz shows the minimum insertion loss of 5dB"on-state",and the isolation of the"off-state"is between 20-40dB,which has preliminary switching characteristics.Via 6V,2μs pulse voltage can achieve the device from the"off"to"on"trigger.