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Cross-section TEM images of contacts to . (a) As-deposited thin film metal structure, showing the uniform thickness nickel and gold layers. (b) Annealed sample, showing the uniform thickness gold layer and rough Ni layer. (c) Low magnification image of annealed sample, showing gold platelets with uniform thickness.
Plan-view TEM of contacts to . (a) Image showing discontinuities in the Au layer (regions of light contrast). Ni inclusions are bound by Au facets. (b) Selected area diffraction pattern along GaN direction indicating that the Au film is epitaxial with the underlying GaN epilayer.
Atomic arrangement at the interface as observed by TEM along the projection. (a) High-resolution TEM image. The (0002) basal plane of GaN is parallel to the (111) plane of gold. (b) Enlarged view of the interface region in (a). (c) Calculated image at a sample thickness of and defocus of . The relative positions of Au, Ga, and N atoms are depicted schematically.
Lattice parameters, interplanar atomic distances relevant to epitaxy on the basal plane of GaN, and electronegativity of the elements involved. The lattices of Ni and Au belong to the space group and GaN to .
Atomic radii of Au, Ga, and N.
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