R&D: Electrical and Structural Properties of Binary Ga–Sb PCM Alloys

Journal of Applied Physics has published an article written by Rubab Ume, Haibo Gong, Vadim Tokranov, Michael Yakimov, SUNY Polytechnic Institute, 257 Fuller Road, Albany, New York 12203, USA, Kevin Brew, IBM AI Hardware Center, 257 Fuller Road, Albany, New York 12309, USA, Guy Cohen, Christian Lavoie, IBM T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598, USA , Sandra Schujman, SUNY Polytechnic Institute, 257 Fuller Road, Albany, New York 12203, USA, Jing Liu, Department of Physics, Manhattan College, Riverdale, New York 10471, USA, Anatoly I. Frenkel, Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, New York 11793, USA, and Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, USA, Karsten Beckmann, Nathaniel Cady, and Serge Oktyabrsky, IBM AI Hardware Center, 257 Fuller Road, Albany, New York 12309, USA.

Abstract: “Material properties of Ga–Sb binary alloy thin films deposited under ultra-high vacuum conditions were studied for analog phase change memory (PCM) applications. Crystallization of this alloy was shown to occur in the temperature range of 180–264 °C, with activation energy >2.5 eV depending on the composition. X-ray diffraction (XRD) studies showed phase separation upon crystallization into two phases, Ga-doped A7 antimony and cubic zinc-blende GaSb. Synchrotron in situ XRD analysis revealed that crystallization into the A7 phase is accompanied by Ga out-diffusion from the grains. X-ray absorption fine structure studies of the local structure of these alloys demonstrated a bond length decrease with a stable coordination number of 4 upon amorphous-to-crystalline phase transformation. Mushroom cell structures built with Ga–Sb alloys on ø110 nm TiN heater show a phase change material resistance switching behavior with resistance ratio >100 under electrical pulse measurements. TEM and Energy Dispersive Spectroscopy (EDS) studies of the Ga–Sb cells after ∼100 switching cycles revealed that partial SET or intermediate resistance states are attained by the variation of the grain size of the material as well as the Ga content in the A7 phase. A mechanism for a reversible composition control is proposed for analog cell performance. These results indicate that Te-free Ga–Sb binary alloys are potential candidates for analog PCM applications.“

Acknowledgments:
This work was supported by the Semiconductor Research Corporation (Task 2960) and the SUNY-IBM AI Collaborative Research Alliance. XAFS analysis by AIF was supported by the National Science Foundation under Grant No. DMR 1911592. This research used beamline 7-BM (QAS) of the National Synchrotron Light Source II, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory (BNL) under Contract No. DE-SC0012704. The QAS beamline operations were supported in part by the Synchrotron Catalysis Consortium (U.S. DOE, Office of Basic Energy Sciences, Grant No. DE-SC0012335). The authors would like to acknowledge Steven Ehrlich and Lu Ma of 7-BM for their technical assistance.