Memory switching of ZnGa₂Se₄ thin films as a new material for phase change memories (PCMs)

ZnGa₂Se₄ thin films were prepared by using thermal evaporation technique. X-ray diffraction patterns revealed the amorphous nature of the as- deposited films. The dc conductivity was studied as a function of temperature and thickness. The obtained results of dc electrical conductivity showed its semiconductor behavior and can be explained according to Mott and Davis model. The conduction activation energy ΔE_σ has one value for each thickness indicating the presence of one conduction mechanism through the studied range of temperature. Both dynamic and static I-V characteristic curves of amorphous ZnGa₂Se₄ thin films for switching and memory behavior have been studied as a function of thickness in the range (136-260 nm) and temperature in the range (305-373 K). I-V characteristic curves showed a memory switching at the threshold point [turnover point (TOP)] from the high resistance state (OFF state) to the low resistance state (ON state). The mean value of threshold voltage V̄th increases linearly with increasing the film thickness while decreases exponentially with the increase of temperature. The mean value of the threshold electrical field Eth decreases exponentially with increasing temperature. The values of threshold activation energy ε and threshold resistance activation energy ΔE_R were calculated. The rapid transitions between the high resistive and conductive states were attributed to an electrothermal model initiated from Joule heating of current channel.