Transparent and electrically conductive GaSb/Si direct wafer bonding at low temperatures by argon-beam surface activation

Direct wafer bonds of the material system n-GaSb/n-Si have been achieved by means of a lowtemperature 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 degrees 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 m Omega cm(2) were reached reproducibly. These promising results make the monolithic integration of GaSb on Si attractive for various applications. (C) 2015 The Authors. Published by Elsevier B.V.