MRS Bulletin

Technical Feature

Technical Feature

Overview of Phase-Change Chalcogenide Nonvolatile Memory Technology

S. Hudgens and B. Johnson


Phase-change nonvolatile semiconductor memory technology is based on an electrically initiated, reversible rapid amorphous-to-crystalline phase-change process in multicomponent chalcogenide alloy materials similar to those used in rewriteable optical disks. Long cycle life, low programming energy, and excellent scaling characteristics are advantages that make phase-change semiconductor memory a promising candidate to replace flash memory in future applications. Phase-change technology is being commercialized by a number of semiconductor manufacturers. Fundamental processes in phase-change semiconductor memory devices, device performance characteristics, and progress toward commercialization of the technology are reviewed.


  • chalcogenides;
  • nonvolatile memory;
  • phase change.

Stephen Hudgens is director of research and chief technical officer at Ovonyx Inc. His research interest is primarily in the electrical properties of amorphous tetrahedral and chalcogenide alloy semiconductors, and he has been involved in the commercialization of a number of amorphous semiconductor-based technologies, including thin-film amorphous silicon solar cells and photoreceptor drums and chalcogenide alloy nonvolatile memory devices.

Hudgens received a PhD degree in physics from the University of Chicago in 1976. He was a postdoctoral fellow at MIT and a senior research physicist at Eastman Kodak Research Labs prior to joining the staff of Energy Conversion Devices in 1980. He was director of research at Energy Conversion Devices in 1999 when Ovonyx was formed. He is a member of the American Physical Society and the Materials Research Society.

Hudgens can be reached by e-mail at

Brian Johnson is a senior design engineer at Intel Corporation. His engineering work at Intel began with flash memory characterization and development, followed by device and process enhancement on four generations of Pentium microprocessors. In recent years, he has pursued advanced memory development with chalcogenide phase-change materials in a joint development program between Intel and Ovonyx Inc. Earlier work at Fairchild Research Center, ATT Technologies, and Solar Energy Systems involved light-wave devices with III–V materials and photovoltaic II–VI devices. He received an MS degree in physics from Wayne State University in 1971.

Johnson can be reached by e-mail at