Future Trends in Microelectronics: From Nanophotonics to Sensors to Energy

Chalcogenide Glassy Semiconductors – Could They Replace Silicon in Memory Devices?

K. D. Tsendin

Ioffe Physical-Technical Institute of Russian Academy of Sciences St. Petersburg, Russia

1.   Introduction

The phase-change memory in the chalcogenide glassy semiconductors based on a “crystal-glass” phase transition has been known since the mid-1960’s.¹ The discovery of this phenomenon was not accidental, but was based on an understanding of the semiconducting properties of chalcogenide glassy semiconductors (CGS), which were discovered at loffe institute in 1955.²

Chalcogenide glassy semiconductors are semiconducting glasses incorporating elements of the VI group of the periodic table, such as sulfur, selenium, and tellurium. The ability of Ge-Te glasses to undergo fast crystalline-amorphous phase transition induced by a laser beam is being used in rewritable optical media, such as read/write CDs and DVDs. Moreover, a crystalline-amorphous phase transition may be produced by Joule heating due to an electric current. Accordingly, switching from a high (amorphous) to a low (crystalline) resistance state can be therefore used as a solid-state electronic memory, the more so as the resistance may be changed by many orders of magnitude.

The first generation of memory cells based on current-induced “crystal-glass” phase transitions was fabricated in the late 1970’s. Unfortunately, these first-generation memory cells were prone to frequent data loss and hence unsuccessful. This failure can ...