A transmission electron microscopy study of optically annealed ohmic contacts to GaAs using a Zirconium Diboride diffusion barrier
✍ Scribed by M.P. Grimshaw; A.E. Staton-Bevan
- Publisher
- Elsevier Science
- Year
- 1989
- Tongue
- English
- Weight
- 699 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0921-5107
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✦ Synopsis
7he morphology of a nickel (5 nm), gold (45 nm), germanium (20 nm) ohmic contact to GaAs with a ZrB 2 (50nm) diffusion barrier, annealed to temperatures between 355 and 485 °C, was studied by transmission electron microscopy. The barrier was found to remain intact and unreacted after annealing. The contact annealed to 355 °C reacted in the solid state to form a -Au-Ga, germanium and orthorhombic NiGe phases. 7he morphology of contacts annealed above the melting point of the Ni-Au-Ge mixture consisted of two regions," type A contained a-Au-Ga and NiGeAs, and type B contained a-Au-Ga, cr'-Au-Ga, NiGe and epitaxial germanium, a-Au-Ga segregated to the contact pad edges on annealing above 400 °C. The transition from rectifying to ohmic behaviour corresponded to annealing above the melting point of the contact. Variations in contact resistance with temperature were related to changes in the contact pad edge (approximately the first O. 7 t~m pad edge) and bulk morphologies.