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Phase Change Materials pp 175–198Cite as

Optical and Electrical Properties of Phase Change Materials

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Abstract

Optical and electrical properties of the phase change material Ge2Sb2Te5 are reviewed for its three phases. Implications of these data for the energy distribution of the density of electron states in the vicinity of the band edges are described. Near-band edge optical data obtained from ellipsometry and optical absorption spectra have been fitted with dispersion equations to determine values of ∼ 0.7 eV for the optical bandgap of the amorphous phase, and ∼ 0.5 eV for the highly conducting fcc and hexagonal phases. Infrared absorption spectra exhibit the effects of free carrier absorption in both crystalline phases. Conductivity at ∼ 300 K is dominated by holes in all three phases; hole concentrations and mobilities are 1020 cm−3 and ∼ 30 cm2/V-s in hexagonal, and 1020 cm-3 and ∼ 1 cm2/V-s in fcc. Temperature dependence of the sheet resistance of thin film Ge2Sb2Te5 documents the dramatic decreases in electrical resistance at the amorphous-to-fcc and fcc-to-hexagonal phase transitions. Comparison of the temperature dependence of the electrical properties in each of the three phases of Ge2Sb2Te5 provides additional insights concerning their conduction mechanisms.

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Authors and Affiliations

  1. Department of Materials Science and the Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, 1-110 Engineering Sciences Building 1101 W. Springfield Ave., Urbana, IL, 61801, USA

    Dr. Bong-Sub Lee

  2. Dept. Head for Administrative and Instructional Affairs, Electrical and Computer Engineering Department, University of Illinois at Urbana-Champaign, 153 Everitt Laboratory, 1406 West Green St, MC-702, Urbana, IL, 61801, USA

    Prof. Stephen G. Bishop (Professor and Assoc.)

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Correspondence to Bong-Sub Lee .

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Editors and Affiliations

  1. IBM Almaden Research Center, 650 Harry Road, San Jose, CA, 95120, USA

    Simone Raoux

  2. 1. Physikalisches Institut (1A), RWTH University of Technology, 52056, Aachen, Germany

    Matthias Wuttig

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Lee, BS., Bishop, S.G. (2009). Optical and Electrical Properties of Phase Change Materials. In: Raoux, S., Wuttig, M. (eds) Phase Change Materials. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-84874-7_9

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