Triclinic deformation and anisotropic strain relaxation of an InAs film on a GaAs(0 0 1) substrate measured by a series of symmetric double crystal X-ray diffraction

Abstract

We presented a series of symmetric double crystal X-ray diffraction (DCXD) measurements, (0 0 4), (2 2 0) and (2 −2 0) diffraction, to investigate the strain relaxation in an InAs film grown on a GaAs(0 0 1) substrate. The strain tensor and rotation tensor were calculated according to the DCXD results. It is found that the misfit strain is relaxed nearly completely and the strain relaxation caused a triclinic deformation in the epilayer. The lattice parameter along the [1 1 0] direction is a little longer than that along the [1 −1 0] direction. Furthermore, a significant tilt, 0.2°, towards the [1 1 0] direction while a very slight one, 0.002°, towards [1 −1 0] direction were discussed. This anisotropic strain relaxation is attributed to the asymmetric distribution of misfit dislocations, which is also indicated by the variation of the full-width at half-maximum (FWHM) of (0 0 4) diffraction along four azimuth angles.