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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 7443-7448 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermally stable, low-resistance p-type ohmic contacts have been developed by depositing NiInW metals on GaAs substrates in which Be and F were coimplanted. The contacts provided resistances of about 1.4 Ω mm after annealing at temperatures in the range of 300–800 °C for short times. The electrical properties did not deteriorate after annealing at 400 °C for more than 100 h, which far exceeds the requirements for current GaAs device fabrication. The present study demonstrated for the first time that thermally stable, low-resistance ohmic contacts to both n- and p-type GaAs can be fabricated using the same metallurgy. In addition, NiInW ohmic contacts were prepared by simultaneous (one-step) annealing for ion-implant activation and contact formation, which simplifies significantly the device fabrication process. A factor-of-2 reduction of the contact resistances was achieved by slight etching of the GaAs surface prior to the contact metal deposition so that the metal/GaAs interface contacted the peak position of the Be concentration in the GaAs substrate. Another method used to reduce the contact resistance was to add a small amount of Mn to the NiInW metals: the resistance decreased with increasing amounts of Mn. The contacts had smooth morphology and shallow depth, less than 70 nm, which is desirable for very-large-scale integration device application.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2468-2474 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of Si or Ge addition to NiInW ohmic contacts on their electrical behavior were studied, where the samples were prepared by evaporating Ni(Si) or Ni(Ge) pellets with In and W and annealed by a rapid thermal annealing method. An addition of Si affected the contact resistances of NiInW contacts: the resistances decreased with increasing the Si concentrations in the Ni(Si) pellets and the lowest value of ∼0.1 Ω mm was obtained in the contact prepared with the Ni-5 at. % Si pellets after annealing at temperatures around 800 °C. The contact resistances did not deteriorate during isothermal annealing at 400 °C for more than 100 h, far exceeding process requirements for self-aligned GaAs metal-semiconductor field-effect-transistor devices. In addition, the contacts were compatible with TiAlCu interconnects which have been widely used in the current Si process. Furthermore, the addition of Si to the NiInW contacts eliminated an annealing step for activation of implanted dopants and low resistance (∼0.2 Ω mm) contacts were fabricated for the first time by a "one-step'' anneal. In contrast, an addition of Ge to the NiInW contacts did not significantly reduce the contact resistances.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6589-6591 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The outdiffusion of Be implanted into GaAs has been found to be identical after capless or capped (Si3N4 or SiO2 ) rapid thermal annealing (RTA) at 900–1000 °C and to depend on the Be dose and its proximity to the surface. The outdiffusion is more pronounced when the Be implant is shallow (〈0.1 μm) and/or the Be+ dose is high (〉1×1015 cm−2 ). It is demonstrated that the Be outdiffusion is driven by the presence of a highly damaged surface layer. Auger results suggest the formation of a BeOx compound at the surface of a high-dose (1×1016 cm−2 ) Be-implanted sample that underwent capless RTA at 1000 °C/1 s. It appears that BeOx formation occurs when the outdiffused Be interacts with the native Ga/As oxides during annealing. All the Be remaining in the GaAs after a 〉900 °C/2 s RTA is electrically active.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 569-571 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: F+ co-implantation at different doses and energies was performed into GaAs already implanted with Be+ at high dose (1015 cm−2) and low energy (20 keV), in order to reduce the beryllium diffusion during post-implant annealing. The redistribution behavior of Be and associated electrical effects were studied by secondary-ion mass spectrometry, transmission electron microscopy (TEM), Hall effect measurements, and current-voltage profiling. Be outdiffusion was reduced by co-implantation of F; more than 80% of the implanted Be was retained during rapid thermal annealing up to 850 °C. The dose and energy of the F implant strongly influenced Be electrical activation efficiency. High activation, up to 48.5%, was obtained when F was co-implanted at high dose (1015 cm−2) and low energy (10 keV). Hole profiles shown reduced electrical activation in the region where F and Be profiles overlapped and TEM studies indicated the formation of {111} coherent plates, possibly BeF2 precipitates, in the same region. The reduction of Be outdiffusion in F co-implanted samples led to high activation after annealing, and was believed to be due to chemical interaction between Be and F.
    Type of Medium: Electronic Resource
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