STRUCTURAL AND ELECTRONIC-PROPERTIES OF GA2SE3

We study the defect tetrahedral semiconductor Ga2Se3 with ordered vaca nt sites using state-of-the-art density-functional calculations. The c alculated main structural properties (the average cubic lattice parame ter, a(0)=10.20 a.u., and the average Ga-Se bond length, r=4.52 a.u.) and electronic properties (the forbidden energy gap, direct, which amo unts to about 2.4 eV) are in good agreement with the experimental data . The role of the coordination defects is analyzed in detail, and the contribution of the different atoms to the electronic density of state s is also discussed. No significant differences are found if the vacan t sites are ordered according to a monoclinic structure rather than or thorhombic, both previously proposed in literature, since the peculiar features of the structural and electronic properties are strongly rel ated to the vacancies and their local environment rather than to their particular ordering. We also discuss the results obtained for the ort horhombic phase pseudomorphically grown on GaAs or ZnSe(001) substrate s. (C) 1998 American Institute of Physics.