Lattice relaxation in InxAl1−xAs/GaAs heterostructure grown on exact oriented and misoriented GaAs substrates

Abstract

We have examined lattice relaxation properties of 2 μm thick InxAl1−xAs epitaxial layers grown simultaneously on a (100) exact oriented GaAs substrate and on a 2° misoriented GaAs substrate by low pressure metalorganic chemical vapor deposition method. Double crystal x-ray diffractometry has been used to determine the alloy compositions at various azimuthal angles. As a result of (400) x-ray rocking curve analysis, it was found that the full width at half-maximum (FWHM) of x-ray rocking curves for both samples were strongly dependent on the azimuthal angle, indicating that the lattice relaxation depended greatly on the substrate orientation. From the data of {511} asymmetric measurements for four different directions, the In contents of the epitaxial layers found were 24%. The In0.24Al0.76As epitaxial layers grown on an exact oriented substrate and on a misoriented substrate both showed 82% relaxation, which was a larger value in comparison with the similarly mismatched InGaAs/GaAs heterostructure. The periodic FWHM of the x-ray rocking curves shows that the anisotropy of residual strain was independent of the nominal substrate misoriented direction. For both types of substrate, it is most likely that the variation of the FWHM originates from asymmetric densities of misfit dislocation.