Twist wafer bonded ''fixed-film'' versus ''compliant'' substrates: Correlated misfit dislocation generation and contaminant gettering

Compliant film substrates, which ideally are free-standing thin-film substrates, can be used to grow lattice-mismatched hetero-epitaxial films without misfit dislocation generation to thicknesses beyond the usual critical conditions, because the elastic strain is shared by the epitaxial and the substrate films. Some recent studies have shown that heteroepitaxial films of superior quality have been grown on thin substrate films fixed to bulky handle wafers obtained via the wafer-bonding method at a rotation angle, which produced a relaxed twist boundary consisting of a screw dislocation network. We consider it as highly unlikely that during growth of the hetero-epitaxial film such a fixed film can be elastically deformed to resemble a free-standing compliant thin-film substrate. In this rapid communication, a tentative interpretation of the role of the fixed-film substrate in producing high-quality hetero-epitaxial films is presented: (i) the screw dislocations gettered away contaminants that would otherwise lead to the generation of growth stacking faults; and (ii) the screw dislocations also allowed the misfit dislocations to be generated in a correlated way so that few threading dislocation segments were left in the bulk of the hetero-epitaxial film.