CRITICAL THICKNESS DETERMINATION OF INAS, INP AND GAP ON GAAS BY X-RAY INTERFERENCE EFFECT AND TRANSMISSION ELECTRON-MICROSCOPY

X-ray interference effect, reflection high-energy electron diffraction , and transmission electron microscopy were used to determine the crit ical thickness of InAs, InP and GaP on GaAs {001} grown by atomic laye r molecular beam epitaxy. Three different series of samples consisting in N monolayers of InAs (N = 1, 2, 3, 4), M monolayers of InP (M = 3, 4, 5, 6, 7) and L monolayers of GaP (L = 2, 3, 4, 5, 6, 9) covered by a 200 nm GaAs cap layer were grown at 350-degrees-C. The thicknesses of the strained layers were chosen to cover the range from strained la yers (below the critical thickness for generation of misfit dislocatio ns) to relaxed layers (where all lattice mismatch is relieved by the g eneration of misfit dislocations). Sample growth was monitored by refl ection high-energy electron diffraction in order to in-situ study the relaxation process. X-ray interference effect was used to determine th ickness and strain status of the strained layers comparing experimenta l diffraction patterns with simulated ones using dynamical theory of X -Tay diffraction. Transmission electron microscopy was used to assess thickness, relaxation status and dislocation nucleation in the straine d layer.