Long-range order in In_xGa_1-xAs

We have found by electron diffraction that In0.5Ga 0.5As thin crystals, grown on InP substrates by molecular beam epitaxy along the 〈110〉 direction, exhibit a long-range order identical to those observed previously in the AlxGa1-xAs alloy system. In the ordered In0.5Ga0.5As structure, the 0, 0, 0 and 1/2, 1/2, 0 sites in each unit cell are preferentially occupied by Ga atoms, and the 1/2, 0, 1/2 and 0, 1/2, 1/2 sites are occupied by In atoms. Our diffraction results also indicate the presence of a high density of antiphase boundaries in the ordered In0.5Ga0.5As phase.