The crystal structure of (In1-xGax)2Se3, where x was between 0.08 and 0.40, was grown by means of vapor transport, and was studied by using electron diffraction and high-resolution electron microscopy. The crystal structure was of defect wurtzite type, and one third of the cation sites were vacant. These structural vacancies were ordered so as to form screws along the c-axis. The space group was P61 or P65, and the lattice constants were a = 0.692nm and c = 1.887nm when x = 0.38. This suggested that the lattice mismatch between the c-plane and the (111) plane of GaAs became equal to zero. Systematic displacements of atoms from the atomic positions of the ideal wurtzite structure were easily described in terms of displacements of the 2-coordinated Se atoms around the vacancies. These were a 30 rotation of the 2-coordinated Se atom towards the [001] direction, and a 9% shrinkage of the bond length between the 2-coordinated Se atom and the 2 neighboring group-III atoms.

J.Ye, Y.Nakamura, O.Nittono: Philosophical Magazine A, 1996, 73[1], 169-86