Elastically strain-relaxed GaAs/In 0.08 Ga 0.92 As/GaAs heterostructures on GaAs (0 0 1) substrates were fabricated by the in-place bonding method. Pseudomorphic heterostructures were patterned and an underlying sacrificial AlAs layer was removed by selective etching. As the GaAs/InGaAs/GaAs structure is released from the substrate, elastic strain relaxation occurs in agreement with a force-balance model and the strain-relaxed structures are weakly bonded in place to the substrate. The bond between the strain-relaxed structure and the substrate was subsequently strengthened by annealing at 400 • C. The increase in the in-plane lattice parameter of these bonded GaAs/In 0.08 Ga 0.92 As/GaAs structures is 0.25-0.37%.

Bonding of elastically strain-relaxed GaAs/InGaAs/GaAs heterostructures has been achieved on GaAs(001) substrates by the method of in-place bonding. Pseudomorphic heterostructures were patterned and a sacrificial AlAs layer was removed by selective etching. As etching proceeds and the GaAs/InGaAs/GaAs structure is released from the substrate, elastic strain relaxation occurs and the strain-relaxed structures are weakly bonded in-place to the substrate. The bond between the strain-relaxed structure and the substrate was then strengthened by annealing under conditions similar to those used for whole wafer bonding of GaAs. The degree of strain relaxation of the InGaAs layer is determined by the relative thickness of the GaAs and InGaAs layers. The increase in the in-plane lattice parameter of these bonded GaAs/InGaAs/GaAs structures is 0.3-0.4%.

Engineered or 'virtual' substrates are of interest to extend the range of epitaxially-grown semiconductor heterostructures available for device applications. To this end, elastically strain-relaxed square features up to 30 μm in size and having an in-plane lattice constant as much as 0.49% larger than the lattice constant of GaAs were fabricated from MOCVD-grown GaAs/In 0.08 Ga 0.92 As/GaAs heterostructures by the in-place bonding method, using either AlAs or Al 0.7 Ga 0.3 As as the sacrificial layer. TEM images show that the solution-bonded interface is flat with a network of sessile edge dislocations that accommodates the different in-plane lattice constants of the feature and the GaAs substrate and a small rotation of the bonded features. Micro-Raman spectroscopy, which has a spatial resolution of ∼1 μm, was shown to be useful for characterizing lattice mismatch strain 0.0023, i.e. with an order of magnitude lower sensitivity than high-resolution XRD.