Journal of Crystal Growth

In situ detection of misfit dislocations by light scattering

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The in situ detection of strain relaxation from misfit dislocation formation using diffuse light scattering was studied during molecular beam epitaxy (MBE) growth of InGaAs/GaAs(0 0 1). The technique can be implemented for either MBE or metal-organic vapor-phase-epitaxy growth and is sensitive to atomic-scale roughness with correlation lengths in the range 0.4-30 μm, providing information complementary to reflection high energy electron diffraction. An increase in scattering intensity associated with roughening from dislocations is detected above a certain thickness. However, ex situ characterization of quenched samples by transmission electron microscopy, atomic force microscopy (AFM) and X-ray diffraction showed that this onset was associated with roughening from preferential growth associated with misfit dislocations and not to the initial onset of dislocation formation. Information from AFM scans, ex situ optical and soft-X-ray light scattering are compared and show that the detection of lines of steps signaling the first misfit dislocations from strain relaxation was lost in the background signal from the initial roughness of the GaAs substrate buffer surface used in our studies.