Electron beam evaporation deposition and properties of Abrupt GST/Si heterojunction structure

The ternary alloy, Ge₂Te₂Sb₅ is one of the most important compounds of the GeTe-Sb₂Te₃ pseudobinary systems. Ge₂Te₂Sb₅ thin films of thickness of 100 nm-300 nm were deposited by electron beam evaporation. After annealing at different temperatures, we did X-ray diffraction measurement to characterize the structure transformation of the material. In-situ resistance measurement depending on the temperature shows that there is about three orders of magnitude change between the high resistance state (amorphous state) and the low resistance state (face-centered cubic state). To construct a heterojunction diode, we deposited Ge₂Te₂Sb₅ thin films on n-type silicon wafers. Rectification effects were observed in voltage-current measurements of the abrupt heterojunctions. Traditional voltage-current relationship of p-n junctions and metal-semiconductor junctions are used to explain the characteristics of Ge₂Te₂Sb₅/n-Si heterojunctions.