X-ray diffraction characterization of highly strained InAs and GaAs layers on InP grown by metalorganic vapor-phase epitaxy

Abstract

Using high resolution x-ray diffraction highly strained extremely thin InAs and GaAs layers grown on InP substrates by low-pressure metalorganic vapor-phase epitaxy have been studied. In order to determine the growth rate and the layer quality of extremely thin InAs and GaAs different kind of test structures are developed. InAs/In0.53Ga0.47As, GaAs/In0.53Ga0.47As, and InAs/GaAs/In0.53Ga0.47As superlattice structures were prepared, providing independent informations about InAs and GaAs growth rate under high strain, layer quality, and strain compensation effects. A relation was derived, which allows the direct calculation of the layer thicknesses of individual layers within a superlattice, avoiding the time consuming computer fitting. The thicknesses of very thin InAs and GaAs layers can be determined by extracting parameters from the rocking curve. Samples grown with various strained layer thicknesses and periods were analyzed and compared. Dramatic broadening of satellite peaks with increasing InAs thickness was observed, and this is attributed to the three-dimensional growth of InAs highly strained layers and the onset of strain relaxation. Smooth GaAs surfaces seem easier to form, although GaAs layers are under a similar amount of strain as InAs. The effect of period number on the rocking curve quality was also studied. Only in case of coherent growth with good interfaces and small fluctuations the satellite-peak intensities increased with increasing the period number, as theoretically predicted. In addition, strain compensation in the InAs/GaAs/InGaAs SLS’s and InAs/GaAs interface quality was also discussed.