Complete strain relief of heteroepitaxial GaAs on silicon

High quality strain-free heteroepitaxial GaAs-on-Si has been produced by annealing chemically separated GaAs epitaxial layers grown by molecular beam epitaxy directly on silicon substrates. A process sequence has been developed which retains the GaAs layer in place during chemical separation and post-processing, thus maintaining a monolithic fabrication sequence. Using low temperature photoluminescence, it is shown that the majority of the residual strain is eliminated by chemical separation. Subsequent rapid thermal annealing is found to remove the remaining strain and significantly improve material quality. The presented process sequence forms the basis for monolithic integration of high quality strain-free (Al,Ga)As electrical and optical devices with silicon circuitry.