Observation of a novel form of ordering in Al_0.5In_0.5As and (Ga,Al)_0.5In_0.5As

We have found a novel form of ordering in Al0.5In0.5As and (Ga,Al)0.5In0.5As as grown on (001) substrates by molecular beam epitaxy (MBE). Electron diffraction patterns reveal a four-fold periodicity along the [110] direction as well as the more usual two-fold periodicity along 〈111〉 directions. The morphology of the latter type of ordering is also different from its normal form. © 1993.