Ge₂ Sb₂ Te₅ charge trapping nanoislands with high- k blocking oxides for charge trap memory

Charge trap memory capacitors using Ge₂ Sb₂ Te ₅ (GST) nanoislands as charge storage media were fabricated. The GST nanoislands were prepared by plasma-enhanced cyclic chemical vapor deposition on a 6 nm thick tunneling SiO₂ layer. A 16 nm thick Al₂ O₃ or 40 nm thick HfO₂ film was used as the blocking oxide (BO). A shift in the flatband voltage in the capacitance-voltage test was achieved when the GST nanoislands were interposed between the SiO₂ and BOs, highlighting the feasibility of memory applications. The charges were trapped at the interface between the GST and BOs. Stable charge retention up to 104 s was observed.