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 mismatc hed and heterovalent, offering thus an additional flexibility, due to the intrinsic nonbulk character of the band offset at heterovalent jun ctions. Starting with a study of macroscopic and microscopic elasticit y, we evaluate the band offset for several fully relaxed inequivalent interfaces. Both macroscopic strain and microscopic morphology strongl y affect the offset between the topmost Si and GaAs valence bands, whi ch, consequently, is tunable, in principle, by as much as 1.1 eV.