Interface structures in GaAs wafer bonding: Application to compliant substrates

The interface of direct bonded GaAs to GaAs has been studied by scanning transmission electron microscopy and electron energy loss spectroscopy. Voids are seen along the boundary with most being partially filled with a gallium particle. Two general sizes of voids are seen. The large voids (d similar to 45 nm) are distributed in an approximately linear relationship and the smaller (d similar to 12 nm) randomly. In compliant substrates, one of the layers is made thin (less than or equal to 10 nm) and twisted similar to 45 degrees. The larger voids often extend past this thin compliant layer, but no evidence of granularity of the epitaxial film is observed. (C) 2000 American Institute of Physics. [S0003-6951(00)00119-4].