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Interfacial phase-change memory

Nature Nanotechnology volume 6, pages 501–505 (2011)Cite this article

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Abstract

Phase-change memory technology relies on the electrical and optical properties of certain materials changing substantially when the atomic structure of the material is altered by heating1 or some other excitation process2,3,4,5. For example, switching the composite Ge2Sb2Te5 (GST) alloy from its covalently bonded amorphous phase to its resonantly bonded metastable cubic crystalline phase decreases the resistivity by three orders of magnitude6, and also increases reflectivity across the visible spectrum7,8. Moreover, phase-change memory based on GST is scalable9,10,11, and is therefore a candidate to replace Flash memory for non-volatile data storage applications. The energy needed to switch between the two phases depends on the intrinsic properties of the phase-change material and the device architecture; this energy is usually supplied by laser or electrical pulses1,6. The switching energy for GST can be reduced by limiting the movement of the atoms to a single dimension, thus substantially reducing the entropic losses associated with the phase-change process12,13. In particular, aligning the c-axis of a hexagonal Sb2Te3 layer and the 〈111〉 direction of a cubic GeTe layer in a superlattice structure creates a material in which Ge atoms can switch between octahedral sites and lower-coordination sites at the interface of the superlattice layers. Here we demonstrate GeTe/Sb2Te3 interfacial phase-change memory (IPCM) data storage devices with reduced switching energies, improved write-erase cycle lifetimes and faster switching speeds.

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Figure 1: Optical pump–probe testing of IPCM switching behaviour.
Figure 2: Electrical switching characteristics of IPCM devices.
Figure 3: Analysis of the RESET state.

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Acknowledgements

This work was supported by the New Energy and Industrial Technology Development Organization project ‘Research and development of nanoelectronic device technology’. The authors thank Elpida Memory Inc. for device measurement discussions, R. Kondo for technical assistance and S. Cook for reading the manuscript. R.E.S. and M.K. would like to thank the Japanese Society for the Promotion of Science for their research fellowships. All work presented here was performed under the auspices of the Center for Applied Near-Field Optics Research (CAN-FOR).

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Authors and Affiliations

  1. Nanoelectronics Research Institute, National Institute of Applied Industrial Science and Technology, Tsukuba Central 4, 1-1-1 Higashi, Tsukuba, 305-8562, Japan

    R. E. Simpson, P. Fons, A. V. Kolobov, T. Fukaya, M. Krbal & J. Tominaga

  2. SPring-8, Japan Synchrotron Radiation Research Institute (JASRI), Mikazuki Hyogo, 679-5198, Japan

    P. Fons & A. V. Kolobov

  3. National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 3, 1-1-1 Umezono, Tsukuba, 305-8563, Ibaraki, Japan

    T. Yagi

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Contributions

J.T. conceived and designed the entropy controlled interfacial phase-change memory structures. J.T., R.E.S. and T.Y. performed the experiments. R.E.S. wrote the paper. All authors analysed the results and contributed to the discussion presented in the manuscript.

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Correspondence to R. E. Simpson or J. Tominaga.

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Simpson, R., Fons, P., Kolobov, A. et al. Interfacial phase-change memory. Nature Nanotech 6, 501–505 (2011). https://doi.org/10.1038/nnano.2011.96

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