Role of interface strain in a lattice-matched heterostructure

First-principles total-energy-minimization calculations show that the interface bonds are significantly strained in nominally lattice-matched ${\mathrm{In}}_{0.53}$ ${\mathrm{Ga}}_{0.47}$As/InP(001) heterostructures, in agreement with recent x-ray measurements. Anion intermixing at the interface reduces this strain. The calculated valence-band offset is sensitive to interface bond lengths so an energetically (meta)stable interface structure must be used. Then the calculated valence-band offset is independent of intermixing (hence measured strain) and in quantitative agreement with experiment.