Solid-solution strengthening in ordered InxGa₁ −xP alloys

Ordered In x Ga1 − x P alloys have been grown on to GaAs(001) substrates by metal–organic vapour-phase epitaxy. Lattice-matched compositions of alloys (In x Ga1 − x P with x ≈ 0.5) were used in order to produce epitaxial layers free of structural defects (threading dislocations). Growth temperature and substrate orientation were adjusted to control the degree η, of order, of the alloys in the range 0.3–0.5. Nanoindentation tests were carried out to measure the mechanical response of the heteroepitaxial layers. Transmission electron microscopy was used to characterize the structure as well as the plastic zones generated into the specimen by nanoindentation. Comparison of the alloys with binary references (InP and GaP bare substrates) showed strengthening, with the hardness and flow-stress values that are much larger than those of InP and of the same order of magnitude as those of GaP.