Structure investigations of low-temperature MBE grown InAlAs layers on InP[001] substrate

The real crystal structure of In/sub 0.52/AI/sub 0.48/As layers grown on InP<001> substrate as a function of the growth temperature (between 150/spl deg/C and 450/spl deg/C) was investigated. Both as-grown and annealed samples (500/spl deg/C) show a high electrical resistivity (10/sup 6-10/sup 7//spl Omega/cm). The following structural /electrical analyses were applied to these samples: transmission electron microscopy (TEM), x-ray diffraction, particle induced x-ray emission (PIXE). In the temperature range between 200/spl deg/C and 450/spl deg/C good crystalline InAlAs layers can be achieved with a low density of dislocations and stacking faults. A generation of precipitates as in the case of LT-GaAs could not be observed. Furthermore, ordering of group-III elements on {111} planes was observed in these layers. Structure models of such ordered domains are discussed. At growth temperatures below 300/spl deg/C additional As (/spl ap/1-2%) is incorporated in the lattice. For layers grown below 200/spl deg/C "pyramidal defects" are formed containing small inclusions of hexagonal As precipitates in the core of these defects.