Recordings and Analysis of Atomic Ledge and Dislocation Movements in InGaAs to Nickelide Nanowire Phase Transformation.

The formation of low resistance and self-aligned contacts with thermally stable alloyed phases is a prerequisite for realizing reliable functionality in ultrascaled semiconductor transistors. Detailed structural analysis of the phase transformation accompanying contact alloying can facilitate contact engineering as transistor channels approach a few atoms across. Original in situ heating transmission electron microscopy studies are carried out to record and analyze the atomic scale dynamics of contact alloy formation between Ni and In Ga As nanowire channels. It is observed that the nickelide reacts on the In Ga As (111) || Ni In Ga As (0001) interface with atomic ledge propagation along the Ni In Ga As [101¯0] direction. Ledges nucleate as a train of strained single-bilayers and propagate in-plane as double-bilayers that are associated with a misfit dislocation of b→=2c3[0001]. The atomic structure is reconstructed to explain this phase transformation that involves collective gliding of three Shockley partials in In Ga As lattice to cancel out shear stress and the formation of misfit dislocations to compensate the large lattice mismatch in the newly formed nickelide phase and the In Ga As layers. This work demonstrates the applicability of interfacial disconnection (ledge + dislocation) theory in a nanowire channel during thermally induced phase transformation that is typical in metal/III-V semiconductor reactions.