Direct wafer bonds of the material system n-GaSb/n-Si have been
achieved by means of a low-temperature direct wafer bonding process, enabling an
optical transparency of the bonds along with a high electrical conductivity of
the boundary layer. In the used technique, the surfaces are activated by
sputter-etching with an argon fast-atom-beam (FAB) and bonded in ultra-high
vacuum. The bonds were annealed at temperatures between 300 and 400 °C, followed
by an optical, mechanical and electrical characterization of the interface.
Additionally, the influence of the sputtering on the surface topography of the
GaSb was explicitly investigated. Fully bonded wafer pairs with high bonding
strengths were found, as no blade could be inserted into the bonds without
destroying the samples. The interfacial resistivities of the bonded wafers were
significantly reduced by optimizing the process parameters, by which Ohmic
interfacial resistivities of less than 5 mΩ cm2 were reached
reproducibly. These promising results make the monolithic integration of GaSb on
Si attractive for various applications.