Elastically Strain-Relaxed GaAs/InGaAs/GaAs Heterostructures on GaAs(001)

Engineered substrates with surface regions having an in-plane lattice parameter different from that of available semiconductor wafers are of interest to extend the properties of semiconductor devices. This was achieved by bonding strain-relaxed GaAs/In$_{0.08}$Ga$_{0.92}$As/GaAs structures on GaAs(001) substrates. Pseudomorphic heterostructures having a lattice mismatch of 0.56{\%} were grown by metal-organic chemical vapor deposition (MOCVD) and patterned using conventional photolithography to define arrays of 10 or 20 micron square structures. A sacrificial AlAs layer was then removed by selective etching with HF. During etching, the strained structures relax elastically, without introducing misfit dislocations, and bond weakly in-place to the substrate. The degree of strain relaxation of the InGaAs layer is determined by the relative thickness of the GaAs and InGaAs layers in agreement with a force balance model.\footnote{G.M. Cohen, et al., App. Phys. Lett. \textbf{86}, 251902 (2005).} The bond was then strengthened by annealing at 400$^{\circ}$C for 2hrs, while stabilizing the surface with TBAs in the MOCVD reactor. The increase in the in-plane lattice parameter of the bonded structures compared to the GaAs substrate was 0.25-0.44{\%}.