atomic scale dynamics of contact formation in the cross-section and along the channel of ingaas nanowires

Department: Electrical & Computer Engineering
Faculty Advisor(s): Shadi A. Dayeh

Primary Student
Name: Renjie Chen
Phone: 858-534-6940
Grad Year: 2018

Alloyed contacts, formed by thermal annealing of metal-semiconductor nanowires (NWs), are prescribed for lithography-free self-aligned gate processes. Prior research on nanoscale metallization has revealed large differences with their bulk counterparts, evoking reevaluation of the thermodynamics, kinetics, and resultant phases in alloyed and compound nanoscale contacts. The in situ heating inside a transmission electron microscope (TEM) permitted imaging of the atomic scale dynamics in contact phase transformation in elemental Si and Ge NWs but not yet in III-V NW channels. Here, we carried out in-situ heating TEM experiments to study the dynamics of contact metallization between Ni and In0.53Ga0.47As NW channels fabricated by top-down method, and observed at atomic resolution the initial stages of ledge formation and movement behaviors of Ni2In0.53Ga0.47As (nickelide) in both the NW cross-section and along the NW channel. In the square cross-section of a <110> oriented InGaAs NW that is composed of {100} and {110} side-wall facets, the nickelide reacted in a layer-by-layer manner with ledge formation and movement on {111} facets and along <112> directions. To limit the naturally occurring intermixing between Ni and InGaAs NW due to latent heat during metal deposition, we tailored the interfacial structure of the InGaAs NW and found significant changes in the contact formation dynamics, captured by a model that was specifically developed for the cross-sectional geometry of NW channels. The dynamics of the reaction along the NW channel were more revealing. We observed consistent nucleation of strained single-bilayers that rapidly merge to form a stable double-bilayer, which moves on the reaction interface of In0.53Ga0.47As (111) || Ni2In0.53Ga0.47As (0001). The single-bilayer ledges transfer into double-bilayers by collective gliding of Shockley partial dislocations and by forming a misfit dislocation. Consequently, the double-bilayer height became the unit height of the nickelide ledges in this phase transformation. We also monitored the solid-phase-regrowth (SPR) to incorporate dopants at the surface of the InGaAs channel under in situ TEM, and demonstrated the improved contact resistance by fabricating functional InGaAs MISFETs. Our in-situ studies provided guidance for the phase selection of crystalline self-aligned contacts in nanoscale channels cross-sections.

Industry Application Area(s)
Electronics/Photonics | Materials | Semiconductor

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