IN-SITU DETECTION OF MISFIT DISLOCATIONS BY LIGHT-SCATTERING

The in situ detection of strain relaxation from misfit dislocation for mation using diffuse light scattering was studied during molecular bea m epitaxy (MBE) growth of InGaAs/GaAs(0 O 1), The technique can be imp lemented for either MBE or metal-organic vapor-phase-epilaxy growth an d is sensitive to atomic scale roughness with correlation lengths in t he range 0.4-30 mu m, providing information complementary to reflectio n high energy electron diffraction. An increase in scattering intensit y associated with roughening from dislocations is detected above a cer tain 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 rougheni ng from preferential growth associated with misfit dislocations and no t to the initial onset of dislocation formation. Information from AFM scans, ex situ optical and soft-X-ray light scattering are compared an d 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.