P. Kidd et al., INTERPRETATION OF THE DIFFRACTION PROFILE RESULTING FROM STRAIN RELAXATION IN EPILAYERS, Journal of physics. D, Applied physics, 28(4A), 1995, pp. 133-138
We have studied the profiles of the Bragg peaks and diffuse scattering
in reciprocal space along both the plane perpendicular (q(perpendicul
ar to)) and plane parallel (q(parallel to)) directions for sample stru
ctures consisting of layers of In0.1Ga0.9As grown by molecular beam ep
itaxy on [001] oriented GaAs substrates. The samples have different la
yer thicknesses and different dislocation distributions. We have measu
red the dislocation distributions in the interfaces using plan view tr
ansmission electron microscopy. We find that, for thin layers with low
dislocation densities, the diffraction profiles in both the plane per
pendicular (q(perpendicular to)) and plane parallel (q(l)) can be mode
lled by considering two components of the diffraction profile, namely,
dynamical scattering from the coherently coupled regions of perfect l
ayer between dislocations and diffuse scattering from decoupled region
s around the dislocations. From the q(parallel to) profile a lateral d
imension can be associated with the regions that give rise to the diff
use scattering, and we show that this dimension scales with the layer
thickness. For thicker layers with higher dislocation densities, the s
train fields of the dislocations overlap. In this case the diffraction
profiles in (q(perpendicular to)) are modelled by considering the rat
io of the depth of coherently scattering decoupled crystal, above the
dislocation array, with the total depth of the layer, assuming that sc
attering from the greatly distorted crystal close to the array is lost
. Along q(parallel to) the diffuse scattering is discussed on the basi
s of a statistical distribution of finite correlation lengths and micr
oscopic tilts.