DETERMINATION OF THE CRITICAL THICKNESS OF MISFIT DISLOCATION MULTIPLICATION USING IN-SITU DOUBLE-CRYSTAL X-RAY-DIFFRACTION

Two different kinds of critical thicknesses in the relaxation process were determined by means of in situ synchrotron double-crystal x-ray r eflection topography and in situ synchrotron double-crystal x-ray diff ractometry during the growth of an In0.066Ga0.934As epilayer on a GaAs (001) substrate. The first critical thickness, derived from the in si tu x-ray topographs, has been found to be in agreement with the Matthe ws and Blakeslee theory of misfit dislocation generation. We present m easurements of the lattice constant perpendicular to the interlace emp loying the rocking curves of the symmetric reflection and show that th e deep drop in the plot of the lattice constant versus epilayer thickn ess may be related to misfit dislocation multiplication rather than to misfit dislocation generation processes. Our second critical thicknes s, derived from the in situ x-ray diffraction data has been found to b e in reasonable agreement with recently published theories of misfit d islocation multiplication and substantial relaxation.