Effect of substrate misorientation on x-ray rocking curves from InGaAs relaxed epitaxial layers

Abstract

The effect of substrate misorientation and epitaxial tilt on asymmetrical {hkl} reflections is discussed and a general procedure for characterizing the unit cell geometry of epitaxial layers is proposed. The absolute positions of {hkl} diffraction lines, and hence the line splittings, are derived as a function of the substrate misorientation, epitaxial layer tilt, and azimuthal angle. The procedure is applied to a 3-μm-thick In0.15Ga0.85As layer grown on a misoriented (100) GaAs substrate by recording (400) and {511} reflections as a function of the azimuthal angle. The analysis reveals the presence of residual strain in the epilayer and suggests that relaxation includes a triclinic distortion of the epitaxial film where the [100] direction of the epilayer is not parallel to the [100] direction of the substrate.