Investigation of HfO₂ doping on GeTe for phase change memory

The phase change characteristics of HfO₂ doping on GeTe thin films were investigated by X-ray photoelectron spectroscopy, X-ray diffraction patterns, scanning electron microscope, atom force microscopy, and in situ resistance-temperature measurements. It is shown that the crystallization of amorphous GeTe film could be suppressed by the incorporation of HfO₂, which had a favorable effect on the archival life stability. The activation energy for crystallization increased from 2.36 to 4.69 eV, and the temperature for 10 years data retention increased from 108 to 187 °C with the increasing concentration of HfO₂ form 0 to 12 mol%. Meanwhile, the grain size and surface roughness decreased. Phase change memory based on GeTe-HfO ₂ film was fabricated and characterized. A reversible phase change could be trigged by the pulse with at least 100 ns width which was shorter than that of Ge₂Sb₂Te₅ (500 ns). The resistance ratio between amorphous and crystalline states achieved 500 times. The minimum energy necessary for RESET operation of GeTe-HfO₂ based test cell was much smaller than that of Ge₂Sb₂Te₅-based one.