ELECTRON-MICROSCOPY AND X-RAY-DIFFRACTION DETERMINATIONS OF STRAIN RELEASE IN INGAAS GAAS SUPERLATTICES GROWN BY MOLECULAR-BEAM EPITAXY/

Strain-induced dislocations have been studied in low and medium mismat ched (001) oriented InxGa1-xAs/GaAs superlattice heterostructures. The ir optical quality, composition, residual strain, dislocation nature, and location have been studied by x-ray diffraction and electron micro scopy techniques. Different predictions of the residual strain have be en discussed briefly. All the samples presented perpendicular networks of misfit dislocations with different densities along the [110] and [ 110] directions. The dislocations were confined inside the buffer laye r or at the buffer-superlattice interface without threading the superl attice. A symmetric dislocation movement along the [110] type directio ns were induced by the electron beam in a scanning electron microscope . Panchromatic cathodoluminescence observations allowed the on-line ob servation of the dislocation movement when thickness and composition w ere such that a low linear dislocation density (<2 X 10(3) cm-1) was p resent. The effect was correlated to the different level of metastabil ity of the superlattice. Almost only 60-degrees type misfit dislocatio ns were observed in all the specimens.