Zn-doped Ge2Sb2Te5 (GST) thin films are deposited on glass substrates by an electron-beam evaporation technique in an ultra-high vacuum. GST mixed with 5%, 10%, 20% Zn is used. Through in situ resistance measurements, an increase of crystalline temperature in Zn-doped GST was observed. From absorption spectra, the optical bandgap values of 10% Zn-doped GST in different structures are estimated to be 1.1, 0.9, and 0.7 eV, respectively, which are slightly wider than that of pure GST. A prototype phase-change memory (PCM) device using GST thin film doped with Zn was fabricated. The current–voltage test results of the devices show better switching performances in both SET and RESET processes than that of the device using pure GST film. The threshold voltage is greatly increased with the adding of Zn atom with fixed proportion, which can weaken the interaction during the read and write operation of PCM.