Two different critical thicknesses for relaxation were determined by means of  in situ  synchrotron double-crystal X-ray reflection topography and  in situ  synchrotron double-crystal X-ray diffractometry during the growth of an Ga0.934In0.066As epilayer on an (001) GaAs substrate. The first critical thickness, as deduced from  in situ  X-ray topographs, was found to agree with the Matthews-Blakeslee theory of misfit dislocation generation. The lattice constant, perpendicular to the interface, was deduced from rocking curve measurements of the symmetrical reflections. This showed that a sharp drop in the lattice constant, as a function of epilayer thickness, could be related to misfit dislocation multiplication rather than to misfit dislocation generation. The second critical thickness, as derived from  in situ  X-ray diffraction data, was found to be in reasonable agreement with recently published theories of misfit dislocation multiplication and relaxation.

P.Möck, B.K.Tanner, C.R.Li, A.M.Keir, A.D.Johnson, G.Lacey, G.F.Clark, B.Lunn, J.C.H.Hogg: Semiconductor Science and Technology, 1996, 11[7], 1051-5