Browsing by Author "Reeves, GK"

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    dLow temperature of formation of nickel germanide by reaction of nickel and crystalline germanium
    (Springer Nature, 2014-12) Algahtani, F; Leech, PW; Reeves, GK; Holland, AS; Blackford, MG; Thorogood, GJ; McCallum, JC; Johnson, BC
    The formation of nickel germanide has been examined over a range of low temperatures (200-400 °C) in an attempt to minimize the thermal budget for the process. Cross-sectional Transmission Electron Microscopy (TEM) was used to determine the texture of the germanide layer and the morphology and constituent composition of the Ge/NiGe interface. The onset and completion of reaction between Ni and Ge were identified by means of a heated stage in combination with in-situ x-ray diffraction (XRD) measurements. The stages of reaction were also monitored using measurements of sheet resistance of the germanides by the Van der Pauw technique. The results have shown that the minimum temperature for the initiation of reaction of Ni and Ge to form NiGe was 225 °C. However, an annealing temperature > 275 °C was necessary for the extensive (and practical) formation of NiGe. Between 200 and 300 °C, the duration of annealing required for the formation of NiGe was significantly longer than at higher temperatures. The stoichiometry of the germanide was very close to NiGe (1:1) as determined using energy dispersive spectroscopy (EDS).
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    Low temperature of formation of nickel germanide on crystalline germanium
    (IEEE, 2014) Flgahtani, F; Blackford, MG; Alnassar, MSN; Reeves, GK; Leech, PW; Pirogova, E
    Germanides are conveniently formed by heating a metal layer on germanium and are suitable for forming low resistance ohmic contacts. Many metals form germanides this way and nickel germanide in the form of NiGe is advantageous for use in germanium semiconductor devices as it has a low resistivity comparable to that of NiSi which is a well known electrical contact material in silicon devices. Other forms of nickel germanide, other than NiGe, are not desirable as they have higher resistivities [1]. Thin films of NiGe conveniently form at the relatively low temperature of 300C in a matter of minutes and at lower temperatures over a longer time. Here we report on the heat treatment required to form NiGe on n and p-type germanium at low temperatures (300C and lower) and report on the temperature duration required for fully reacting Ni of different thicknesses to form NiGe. Ni was deposited on crystalline germanium and heat treatments undertaken on several samples for time durations at different temperatures of 5 minutes to 12 hour. © 2014 IEEE