STRUCTURE OF GA0.47IN0.53AS EPITAXIAL LAYERS GROWN ON INP SUBSTRATES AT DIFFERENT TEMPERATURES

The evolution of defect structures and surface reconstruction of Ga0.4 7In0.53As epitaxial layers grown by molecular beam epitaxy on InP subs trate have been investigated by TEM and RHEED over a wide growth tempe rature range (150 degrees C less than or equal to T-g less than or equ al to 450 degrees C) before and after annealing. In the growth tempera ture range 400 degrees C less than or equal to T-g less than or equal to 450 degrees C, extensive segregation of In near the layer surface t akes place. The maximum of In concentration was found to lie under the layer surface. The kinetic of surface pit formation after annealing w as explained in terms of surface reconstruction and As clustering. Ext ensive As clustering was observed after annealing for the growth tempe rature range 175 degrees C less than or equal to T-g less than or equa l to 300 degrees C. Analysis of diffuse scattering and dark-field imag es made it possible to propose an atomic model of cluster structure. P recipitate formation close to the interface was observed only for the samples grown at 150 degrees C and annealed at 500 degrees C. Differen ces in electrical properties between LT-grown GaAs and Ga0.47In0.53As are explained in terms of the structural defects.