Multiresistance Characteristics of PCRAM With $ \hbox{Ge}_{1}\hbox{Cu}_{2}\hbox{Te}_{3}$ and $\hbox{Ge}_{2} \hbox{Sb}_{2}\hbox{Te}_{5}$ Films

A phase-change random access memory (PCRAM) with multiresistance characteristics was fabricated. In this multiple PCRAM device, Ge
₂
Sb
₂
Te
₅
(GST) and Ge
₁
Cu
₂
Te
₃
(GCT) are utilized as phase-change materials to realize high and middle-resistance states, respectively. Since GCT has simultaneously lower melting point and higher crystallization temperature than GST, recording of multiple states was directly achieved without any additional step. It was confirmed that multiple resistances of 10
³
, 10
⁴
, and 10
⁵
Ω were measured by a selection of current pulse during crystallization. From this work, it is expected that a device structure with GST and GCT can be one of the candidates for an effective multilevel cell operation in PCRAM.