Free carrier absorption in the Ge:Sb:Te system

González‐Hernández, J.; López-Cruz, E.; Yanez-Limon, M.; Strand, David; Chao, Bing-Fong; Ovshinsky, Stanford R.

doi:10.1016/0038-1098(95)00335-5

Cited by 25 publications

(11 citation statements)

References 6 publications

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“…This indicates that the Ge is incorporated in lattice sites, perhaps substituting the Sb atoms, as previously found in Ge:Sb:Te compounds [15]. From the Full-Width Half-Maximum of the peak at about 28.5 degrees, the crystallite sizes have been estimated (see Table 1).…”

Section: Discussionmentioning

confidence: 98%

Effects of Ge addition on the optical and electrical properties of eutectic Sb70Te30 films

Prokhorov

Mendoza-Galván

González‐Hernández

et al. 2007

Journal of Non-Crystalline Solids

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Section: Discussionmentioning

confidence: 98%

Effects of Ge addition on the optical and electrical properties of eutectic Sb70Te30 films

Prokhorov

Mendoza-Galván

González‐Hernández

et al. 2007

Journal of Non-Crystalline Solids

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“…22 Comparable to pure GeTe, 23 a stable undistorted cubic high-temperature modification does exist; the transition temperature between the rhombohedral and the cubic phases increases with rising GeTe content. Furthermore, a B1-type crystalline phase Ge 4 SbTe 5 ͑=Ge 0.8 Sb 0.2 Te͒, has been described, 15,[24][25][26] this composition point slightly deviates from the compositions corresponding to the pseudobinary GeTe-Sb 2 Te 3 line.…”

Section: Introductionmentioning

confidence: 93%

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

et al. 2010

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Rewritable data-storage media and promising nonvolatile random-access memory are mainly based on phase-change materials ͑PCMs͒ which allow reversible switching between two metastable ͑amorphous and crystalline͒ modifications accompanied by a change in physical properties. Although the phase-change process has been extensively studied, it has not been elucidated how and why the metastable crystalline state is kinetically stabilized against the formation of thermodynamically stable phases. In contrast to thin-film investigations, the present study on bulk material allows to demonstrate how the cubic high-temperature phase of GeTe-rich germanium antimony tellurides ͑GST materials͒ is partially retained in metastable states obtained by quenching of bulk samples. We focus on compositions such as Ge 0.7 Sb 0.2 Te and Ge 0.8 Sb 0.13 Te, which are important materials for Blu-ray disks. Bulk samples allow a detailed structural characterization. The structure of a multiply twinned crystal isolated from such material has been determined from x-ray diffraction data ͑Ge 0.7 Sb 0.2 Te, R3m, a = 4.237 Å, c = 10.29 Å͒. Although the metrics is close to cubic, the crystal structure is rhombohedral and approximates a layered GeTe-type atom arrangement. High-resolution transmission electron microscopy ͑HRTEM͒ on quenched samples of Ge 0.8 Sb 0.13 Te reveal nanoscale twin domains. Cation defects form planar domain boundaries. The metastability of the samples was proved by in situ temperature-dependent powder diffraction experiments, which upon heating show a slow phase transition to a trigonal layered structure at ca. 325°C. HRTEM of samples annealed at 400°C shows extended defect layers that lead to larger domains of one orientation which can be described as a one-dimensionally disordered long-periodical-layered structure. The stable cubic high-temperature modification is formed at about 475°C. Powder diffraction on samples of Ge 0.8 Sb 0.13 Te with defined particle sizes reveal that the formation of the stable superstructure phase is influenced by stress and strain induced by the twinning and volume change due to the cubic → rhombohedral phase transition upon quenching. The associated peak broadening is larger for small crystallites that allow relaxation more readily. Consequently, the degree of rhombohedral distortion as well as the appearance of superstructure reflections upon annealing is more pronounced for small crystallites. The same is true for samples which were slowly cooled from 500°C. Hence, the lattice distortion accompanying the phase transition toward a stable trigonal superstructure is, to a certain degree, inhibited in larger crystallites. This kinetic stabilization of metastable states by stress effects is probably relevant for GST phase-change materials.

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“…While many appreciated the technological possibilities of this rapid switching, Ovshinsky et al spent decades developing useful chalcogenide alloys for both optical and electrical nonvolatile memories. 2,[5][6][7] It is tantalizing that even after significant commercial exploitation of the crystallineamorphous phase transition, much of the basic science, including the mechanism for the transition itself, is not well understood. For example, upon thermal heating, the transition can take minutes 8 rather than nanoseconds.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5] Many of these systems switch between these two states within tens of nanoseconds when exposed to laser light or to electrical current. While many appreciated the technological possibilities of this rapid switching, Ovshinsky et al spent decades developing useful chalcogenide alloys for both optical and electrical nonvolatile memories.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of intrinsic defects in crystalline germanium telluride

et al. 2006

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Germanium telluride undergoes rapid transition between polycrystalline and amorphous states under either optical or electrical excitation. While the crystalline phases are predicted to be semiconductors, polycrystalline germanium telluride always exhibits p-type metallic conductivity. We present a study of the electronic structure and formation energies of the vacancy and antisite defects in both known crystalline phases. We show that these intrinsic defects determine the nature of free-carrier transport in crystalline germanium telluride. Germanium vacancies require roughly one-third the energy of the other three defects to form, making this by far the most favorable intrinsic defect. While the tellurium antisite and vacancy induce gap states, the germanium counterparts do not. A simple counting argument, reinforced by integration over the density of states, predicts that the germanium vacancy leads to empty states at the top of the valence band, thus giving a complete explanation of the observed p-type metallic conduction.

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Free carrier absorption in the Ge:Sb:Te system

Cited by 25 publications

References 6 publications

Effects of Ge addition on the optical and electrical properties of eutectic Sb70Te30 films

Effects of Ge addition on the optical and electrical properties of eutectic Sb70Te30 films

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

Electronic structure of intrinsic defects in crystalline germanium telluride

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