Structural and electronic properties of strained Si/GaAs heterostructures

Band offsets at lattice-mismatched heterojunctions can be tuned owing to their dependence on macroscopic strain, and hence on the substrate composition. The system studied here, GaAs/Si(001), is lattice mismatched and heterovalent, offering thus an additional flexibility, due to the intrinsic nonbulk character of the band offset at heterovalent junctions. Starting with a study of macroscopic and microscopic elasticity, we evaluate the band offset for several fully relaxed inequivalent interfaces. Both macroscopic strain and microscopic morphology strongly affect the offset between the topmost Si and GaAs valence bands, which, consequently, is tunable, in principle, by as much as 1.1 eV.