EFFECT OF SUBSTRATE MISORIENTATION AN X-RAY RACKING CURVES FROM INGAAS RELAXED EPITAXIAL LAYERS

The effect of substrate misorientation and epitaxial tilt on asymmetri cal {hkl} reflections is discussed and a general procedure for charact erizing the unit cell geometry of epitaxial layers is proposed. The ab solute positions of {hkl} diffraction lines, and hence the line splitt ings, are derived as a function of the substrate misorientation, epita xial layer tilt, and azimuthal angle. The procedure is applied to a 3- mu m-thick In0.15Ga0.85As layer grown on a misoriented (100) GaAs subs trate by recording (400) and {511} reflections as a function of the az imuthal angle. The analysis reveals the presence of residual strain in the epilayer and suggests that relaxation includes a triclinic distor tion of the epitaxial film where the [100] direction of the epilayer i s not parallel to the [100] direction of the substrate.