Nonvolatile memory based on phase change in Se-Sb-Te glass

The phase transitions from the amorphous to crystalline states, and vice versa, of Se-Sb-Te films by applying electrical pulses have been studied. This material can be used as nonvolatile memory. The reversible phase transition between the amorphous and crystalline states, which is accompanied by a considerable change in electrical resistivity, is exploited as a means to store bits of information. The nonvolatile memory cells are composed of a simple sandwich structure (metal/chalcogenide thin film/metal). More than 10(4) write/erase cycles were attained by applying electric pulses. In this case, the voltage and pulse width of crystallization and amorphization processes were 2.4 V, 2.0 mus, 2 V and 0.1 mus, respectively. The melting point of the Se-SbTe system is lower than that of the Ge-Sb-Te system, so that the current density for the amorphization process can be decreased to about 30 mA/mum(2).